Sept08

ASTRONOMY

TECHNOLOGY TODAY Your Complete Guide to Astronomical Equipment

A SHOOTING STAR INN • THE APT WEDGE FROM APPLIED PRECISION TECHNOLOGY COLLIMATION MADE EASY FOR A NEWBIE • THE VIRTUAL OBSERVER IMAGE QUALITY AS A FUNCTION OF BACK FOCUS SHIFT FOR CASSEGRAIN SYSTEMS

Vixen VMC200L Mak-Cass and SXD Sphinx Deluxe Equatorial Mount Volume 2 • Issue 9 September 2008 $5.00 US

Contents Industry News

Cover Story Images -29 The VMC200L is an 8-inch aperture, f/9.75 Cassegrain that incorporates a unique meniscus corrector lens positioned between the secondary and primary mirrors and eschews the front mounted corrector of more common Cassegrains. The SXD Mount is a beefier version of the groundbreaking Vixen Sphinx SXW Mount and features control via Vixen’s innovative Star Book handset with star-chart interface. The image of the moon was taken by Jon Betancourt with his VMC200 and a Canon 20D.

ASTRONOMY

TECHNOLOGY TODAY Your Complete Guide to Astronomical Equipment

A SHOOTING STAR INN • THE APT WEDGE FROM APPLIED PRECISION TECHNOLOGY COLLIMATION MADE EASY FOR A NEWBIE • THE VIRTUAL OBSERVER IMAGE QUALITY AS A FUNCTION OF BACK FOCUS SHIFT FOR CASSEGRAIN SYSTEMS

11 UPCOMING EVENTS Summer is Winding Down 12 SKY-WATCHER U.S.A. Synta Optical Technology Establishes U.S. Subsidiary 14 BAADER PLANETARIUM Announce Limited, One-Time Production of Carl Zeiss Abbe II

Vixen VMC200L Mak-Cass and SXD Sphinx Deluxe Equatorial Mount Volume 2 • Issue 9 September 2008 $5.00 US

15 JMI TELESCOPES Prototyping New Lightbridge Accessories Project

In This Issue 8

Editor’s Note Supporting Stellafane with the SDS Scope Project

By Gary Parkerson

29 Vixen VMC200L Mak-Cass and SXD Sphinx Deluxe Equatorial Mount I Guess it’s Possible to Have Your Cake and Eat it Too After All!!

By Erik Wilcox 35 A Shooting Star Inn Sharing Astronomy in the Comfort of a Private and Personal Setting

By Ion Dodd 41 The Virtual Observer A New Breakthrough Technology for the Visual Observer - Part 1

By Roger Blake 49 The APT Wedge from Applied Precision Technology A Wedge that Answers the Challenge!

By Cliff De Lacy

16 EXPLORE SCIENTIFIC Scott Roberts Announces Return to Telescope Manufacturing

53 Collimation Made Easy for a Newbie With a Little Help from Friends!

By Dave Snay 59 Image Quality as a Function of Back Focus Shift for Cassegrain Systems Investigating Popular Cassegrains that Focus Via Changing the Spacing Between the Primary and Secondary Mirrors

By Mike Jones 68 Astro Tips, Tricks, and Novel Solutions The ELF

By Craig Stark

17 PAUL VAN SLYKE AND BLACK FOREST OBSERVATORY A Dream Garage Sale!

18 SIERRA STARS OBSERVATORY Awards Grant to Develop a Software System 19 ROCHESTER INSTITUTE OF TECHNOLOGY New Astrophysical Sciences and Technology Doctorate at RIT Blends Theory, Observation and Instrumentation

Astronomy TECHNOLOGY TODAY

5

Contributing Writers

Contents New Products

Roger Blake is a retired nuclear engineer with a degree in physics from Drexel University in Philadelphia. He has been an amateur astronomer and astrophotographer for 30 plus years. Roger spent his early years in research, but later migrated into the nuclear power industry, responsible for the computer modeling and analysis of reactor physics behavior and thermal margins. He now applies his modeling skills to several astronomy related research and development projects, including the creation of the new Dark Sky Maps and the Virtual Observer.

Cliff De Lacy retired from the Defense Department after 35 years. He has a Master’s degree in HR Management and has taught Nuclear Physics/Radiological Control Fundamentals. A credentialed teacher, he also taught astronomy for the Napa Valley College for Kids Program and is currently a guest teacher in local school districts. He was appointed by JPL in 2003 as a Volunteer Solar System Ambassador for Outreach on NASA missions and enjoys conducting corporate and private star gazing sessions in Northern California. See his Website www.thestarguide.com.

Ian Dodd is a newcomer to astronomy – his curiosity about astronomy was piqued when a family member gave his kids a telescope for Christmas 2007 (a 6-inch Dobsonian).

Although he’s a beginning astronomy observer, Ian has spent thousands of hours peering into eyepieces as a camera operator for film and television.

Mike Jones has been an optical designer and EO/IR engineer for nearly 30 years. He is also an active amateur astronomer and ATM, having made over 55 mirrors and several telescopes. He created the optical designs for numerous systems at McDonald Observatory, Texas A&M University, George Observatory and others. He is a sustaining member of AAVSO, and enjoys classical and blues guitar, birdwatching and photography.

21 WILLIAM OPTICS Introduces a Variety of New Products

22 CATSEYE COLLIMATION/WOOD WONDERS Offers New Fieldcase Designs 23 ORION TELESCOPES & BINOCULARS Introduces Several New Products 25 BAADER PLANETARIUM New LRGBC Anti-Reflection Filters 26 SEAPORT DIGITAL i-Visor Laptop Case Gains Popularity with Astronomers

David Snay is a retired software engineer living in central Massachusetts. He graduated from Worcester Polytechnic Institute and has been an astronomer and astrophotographer for more than 10 years. David currently pursues fine art photography, specializing in traditional black/white images.

Craig Stark, Ph.D. is, by day, a professor whose research involves trying to pull faint signals out of noisy, moving images of people’s brains. By night, he is an amateur astrophotographer and operates Stark Labs which provides software to help users pull faint signals out of noisy, moving images of the heavens.

Erik Wilcox has been observing the sky for more than 20 years. In addition to being a longtime moderator on the popular astronomy forum at www.cloudynights.com, he recently started a new forum at www.starstuffforums.com. When he’s not viewing the sky, he sings and plays guitar in a rock band.

SUBSCRIBERS can now renew their subscription online! www.AstronomyTechnologyToday.com 6

Astronomy TECHNOLOGY TODAY

26 JMI TELESCOPES New Configurable Carry Case

s

S

The Supporting

CAST

The Companies And Organizations That Have Made Our Magazine Possible!

We wish to thank our advertisers without whom this magazine would not be possible. When making a decision on your next purchase, we encourage you to consider these advertisers’ commitment to you by underwriting this issue of Astronomy Technology Today.

20/20 Telescopes and Binoculars www.2020telescopes.com page 36

Catseye Collimation www.catseyecollimation.com page 31

Lunt Solar Systems www.luntsolarsystems.com page 72

ScopeGuard www.scopeguard.com page 30

Adirondack Astronomy www.astrovid.com page 47

CCD-LABS www.ccd-labs.com page 15

Malco Precision www.malcoprecision.com page 30

ScopeStuff www.scopestuff.com page 26

Celestron www.celestron.com page 28

Meade Instruments www.meade.com page 4, 69

DayStar Filters www.daystarfilters.com page 48

MoonLite Telescope Accessories www.focuser.com page 54

Deep Sky Instruments www.deepskyinstruments.com page 43

Oceanside Photo and Telescope www.optcorp.com page 56

Alvin Huey Observing Guides www.faintfuzzies.com page 15

Amateur Astronomy Magazine www.amateurastronomy.com page 43 APM Telescopes www.apm-telescopes.de page 10

Durango Skies www.durangoskies.com page 34

Astro Domes www.astrodomes.com page 64

Explore Scientific www.explorescientific.com page 58

Astro Hutech www.hutech.com page 40

Farpoint Astronomical Research www.farpointastro.com page 45

Astronomical Tours www.astronomicaltours.net page 13

AstroPhoto Insight Magazine www.skyinsight.net page 43 Astro Physics www.astro-physics.com page 9, 51

Glatter Collimation www.collimator.com page 18 Great Red Spot Astronomy www.greatredspot.com page 39 Half Hitch Telescope www.halfhitchtelescope.com page 47

AstroSystems www.astrosystems.biz page 50

Optec www.optecinc.com page 38 Optical Mechanics www.opticalmechanics.com page 31 Optic-Craft Machining www.opticcraft.com page 55 Orion Telescopes and Bionoculars www.oriontelescopes.com page 52 Ostahowski Optics www.ostahowskioptics.com page 26 Pacific Design www.casesandcovers.com page 11 ProtoStar www.fpi-protostar.com page 44

SkyShed Observatories www.skyshed.com page 46 Starizona www.starizona.com page 2 Stark Labs www.stark-labs.com page 64 Starlight Instruments www.starlightinstruments.com page 16 Stellar Technologies International www.stellar-international.com page 57 Stellarvue www.stellarvue.com page 60 Taurus Technologies www.taurus-tech.com page 22 Tele Vue Optics www.televue.com page 70, 71 Teton Telescope www.tetontelescope.com page 55 Thousand Oaks Optical www.thousandoaksoptical.com page 31

iOptron www.ioptron.com page 27

Quantum Scientific Imaging www.qsimaging.com page 24

Jack’s Astro Accessories www.waningmoonii.com page 62

Backyard Observatories www.backyardobservatories.com page 18, 19

Rigel Systems www.rigelsys.com page 25

JMI Telescopes www.jmitelescopes.com page 20

Rubylith www.astro-rubylith.com page 17

Vixen Optics www.vixenoptics.com page 3

The Binoscope Company www.binoscope.com page 39

Kendrick Astro Instruments www.kendrickastro.com page 42

ScopeBuggy www.scopebuggy.com page 32

Woodland Hills Telescopes www.whtelescopes.com page 12

Bobs Knobs www.bobsknobs.com page 44

Lumicon www.lumicon.com page 36

Scope City www.scopecity.com page 14

Zeke’s Seats www.zekesseats.com page 33

Astrozap www.astrozap.com page 17

Van Slyke Instruments www.observatory.org page 39

TO ADVERTISE CONTACT advertise@astronomytechnologytoday.com

ASTRONOMY

TECHNOLOGY TODAY

Volume 2 • Issue 9 September 2008 Publisher Stuart Parkerson

Managing Editor Gary Parkerson

Associate Editors Russ Besancon Karol Birchfield Jessica Parkerson

Art Director Lance Palmer

Staff Photographer Jim Osborne

Web Master Richard Harris

3825 Gilbert Drive Shreveport, Louisiana 71104 info@astronomytechnologytoday.com www.astronomytechnologytoday.com Astronomy Technology Today is published monthly by Parkerson Publishing, LLC. Bulk rate postage paid at Dallas, Texas, and additional mailing offices. ©2008 Parkerson Publishing, LLC, all rights reserved. No part of this publication or its Web site may be reproduced without written permission of Parkerson Publishing, LLC. Astronomy Technology Today assumes no responsibility for the content of the articles, advertisements, or messages reproduced therein, and makes no representation or warranty whatsoever as to the completeness, accuracy, currency, or adequacy of any facts, views, opinions, statements, and recommendations it reproduces. Reference to any product, process, publication, or service of any third party by trade name, trademark, manufacturer, or otherwise does not constitute or imply the endorsement or recommendation of Astronomy Technology Today.

The publication welcomes and encourages contributions; however is not responsible for the return of manuscripts and photographs. The publication, at the sole discretion of the publisher, reserves the right to accept or reject any advertising or contributions. For more information contact the publisher at Astronomy Technology Today, 3825 Gilbert Drive, Shreveport, Louisiana 71104, or e-mail at info@astronomytechnologytoday.com.

8

Astronomy TECHNOLOGY TODAY

Editor’s

Note

Gary Parkerson, Managing Editor

The Stellafane Donation Scope (SDS) has been completed and was presented by Rob Teeter to the Springfield Telescope Makers (STM) at its 73rd annual convention, Stellafane 2008. SDS was so named because it was, from conception, intended for donation to STM for its Flanders Pavilion fund.

Three years ago, the club borrowed to fund the much needed pavilion, which opened in 2006. The 6,000 square-foot structure provides a comfortable venue for lectures and demonstrations during Stellafane and much needed secure storage for the remainder of the year. It enhances the Stallafane experience for the thousands who make the annual pilgrimage to the home of American amateur telescope makers.

SDS is the product of the generosity of a number of contributors, including those in the accompanying alphabetic list, and would not have been possible without the generous investment of time, skill and money by Rob Teeter of Teeter’s Telescopes. Our goal was to create a truly premium telescope and to that end excellent principal optics were provided by Ostahowski Optics and consist of a 12.5-inch f/4.8 Pyrex primary mirror and matched secondary, both certified by interferometry. The primary is supported by a 9-point floatation cell hand crafted by James Grigar of Astro Sky Telescopes in the traditional “Kriege-style.” This remarkable cell was custom configured for optimum function with the specific Teeter design. SDS’s cabinetry was CNC milled by Specialty Millwork of Howell, New Jersey from Teeter’s CAD drawings. The result is a truly professional level of execution. The milled components were given a custom artistic finish that tastefully highlights the woodwork.

SDS’s precision focuser is MoonLite’s dualspeed, tri-knob with compression ring drawtube.

The body of the focuser is superbly anodized in gold, a color that compliments the woodwork finish perfectly. The scope also incorporates MoonLite’s unique ball and socket truss-pole connector system and truss poles. The secondary mirror is supported by ProtoStar’s premium 4vane spider assembly, a design that features very

thin vanes to minimize diffraction and a unique holder that greatly simplifies collimation. The secondary mount includes ProtoStar’s anti-dew heater and is powered without addition of diffraction exaggerating wires.

StellarCAT’s industry leading ServoCAT Jr go-to/tracking drive system was installed and includes its powered ground-board. ServoCAT Jr is a perfect fit for the 12.5-inch SDS and provides fast slew rates, fully automatic tracking and accurate go-to pointing. Go-to coordinates are provided by JMI’s SuperMAX (Argo Navis designed) computer. The feature rich, upgradeable digital telescope control directs the scope to more than 29,000 objects and its LCD display even has a heater for cold weather use.

Controls for both are supported by a Markless Astronomics DSC Stalk II which incorporates a MoonLite clamp and mount block to secure the riser tube. An integrated panel insures clutter-free connection to encoders, controls and input power.

SDS is well equipped for old-school star hopping as well. Included is Stellarvue’s remarkable F50W2 50-mm right-angle finder with illuminated, focusing cross-hair reticle powered by a Rigel Systems PulsGuide Illuminator. Also included is Rigel Systems’ Quikfinder Compact Reflex Sight.

The lucky owner will enjoy matchless views through two eyes as well as one thanks to a Denkmeier binoviewer with the Power x Switch that provides instant selection from two magnifications from a single pair of eyepieces. To make sure a ready pair of eyepieces are on hand, twin Burgess Optical TMB/Burgess 20-mm Stellar Series eyepieces are included. The Stellar Series was designed to take over where the popular TMB/Burgess Planetary line left off and are superb for binoviewing.

The package includes a Tele Vue tunable Paracorr, the accessory that is essential to all fast Newtonians. It tames the coma inherent in the fast f/4.8 optics, significantly increasing the diffraction-limited field of the scope. To insure there’s never an excuse for poor collimation, the

package includes Jim Fly’s Catseye TriplePack Pro XL collimation kit that consists of the Catseye Teletube XL adjustable sight tube, Blackcat XL Cheshire, and Infinity XL autocollimator.

The primary mirror is protected from stray light, dew and dropped objects by a custom truss-shroud from Shrouds by Heather. This form-fitting, curve-hugging, esthetically-pleasing accessory will not sag into the optical path and there are no draw-strings to break or tie-downs to fumble with. The ProtoStar dew heater is controlled via a Kendrick Astro Instruments DigiFire 7 controller and all SDS electronics can be powered by the included Celestron Power Tank 17, both from 20/20 Telescopes.

Design and construction of SDS has been documented by Rob Teeter in a series of articles that will continue with the October 2008 issue of ATT and a subsequent announcement will be published here when the date of the auction of SDS has been set by STM. Meanwhile, we want to encourage all to contribute directly to the Flanders Pavilion cause. For more information on donation opportunities, please visit www.stellafane.org/help/pavilion.html.

SDS PROJECT CONTRIBUTORS 20/20 Telescopes and Binoculars (www.2020telescopes.com) AstroSky Company (www.astrosky.homestead.com/Astrosky.html) Burgess Optical (www. burgessoptical.com) Catseye Collimation (www.catseyecollimation.com) Denkmeier Optical (www.deepskybinoviewer.com) JMI Telescopes (www.jimsmobile.com) Markless Astronomics (www.marklessastronomics.com) MoonLite Telescope Accessories (www.focuser.com) Ostahowski Optics (www.ostahowskioptics.com) ProtoStar (www.fjp-protostar.com) Rigel Systems (www.rigelsys.com) Shrouds by Heather (www.teeterstelescopes.com) StellarCAT (www.stellarcat.com) Stellarvue (www.stellarvue.com) Tele Vue (www.televue.com)

The new Astro-Physics 6" Eagle Adjustable Folding Pier is a versatile work-of-art as well as a totally practical tool for the advanced imager.

The one piece assembly sets up quickly in the field and allows adjustment of pier height, leveling of the mount, and eases the process of polar alignment.

www.astro-physics.com • 815-282-1513 Astronomy TECHNOLOGY TODAY

9

s

S

The Supporting

CAST

The Companies And Organizations That Have Made Our Magazine Possible!

We wish to thank our advertisers without whom this magazine would not be possible. When making a decision on your next purchase, we encourage you to consider these advertisers’ commitment to you by underwriting this issue of Astronomy Technology Today.

20/20 Telescopes and Binoculars www.2020telescopes.com page 36

Catseye Collimation www.catseyecollimation.com page 31

Lunt Solar Systems www.luntsolarsystems.com page 72

ScopeGuard www.scopeguard.com page 30

Adirondack Astronomy www.astrovid.com page 47

CCD-LABS www.ccd-labs.com page 15

Malco Precision www.malcoprecision.com page 30

ScopeStuff www.scopestuff.com page 26

Celestron www.celestron.com page 28

Meade Instruments www.meade.com page 4, 69

DayStar Filters www.daystarfilters.com page 48

MoonLite Telescope Accessories www.focuser.com page 54

Deep Sky Instruments www.deepskyinstruments.com page 43

Oceanside Photo and Telescope www.optcorp.com page 56

Alvin Huey Observing Guides www.faintfuzzies.com page 15

Amateur Astronomy Magazine www.amateurastronomy.com page 43 APM Telescopes www.apm-telescopes.de page 10

Durango Skies www.durangoskies.com page 34

Astro Domes www.astrodomes.com page 64

Explore Scientific www.explorescientific.com page 58

Astro Hutech www.hutech.com page 40

Farpoint Astronomical Research www.farpointastro.com page 45

Astronomical Tours www.astronomicaltours.net page 13

AstroPhoto Insight Magazine www.skyinsight.net page 43 Astro Physics www.astro-physics.com page 9, 51

Glatter Collimation www.collimator.com page 18 Great Red Spot Astronomy www.greatredspot.com page 39 Half Hitch Telescope www.halfhitchtelescope.com page 47

AstroSystems www.astrosystems.biz page 50

Optec www.optecinc.com page 38 Optical Mechanics www.opticalmechanics.com page 31 Optic-Craft Machining www.opticcraft.com page 55 Orion Telescopes and Bionoculars www.oriontelescopes.com page 52 Ostahowski Optics www.ostahowskioptics.com page 26 Pacific Design www.casesandcovers.com page 11 ProtoStar www.fpi-protostar.com page 44

SkyShed Observatories www.skyshed.com page 46 Starizona www.starizona.com page 2 Stark Labs www.stark-labs.com page 64 Starlight Instruments www.starlightinstruments.com page 16 Stellar Technologies International www.stellar-international.com page 57 Stellarvue www.stellarvue.com page 60 Taurus Technologies www.taurus-tech.com page 22 Tele Vue Optics www.televue.com page 70, 71 Teton Telescope www.tetontelescope.com page 55 Thousand Oaks Optical www.thousandoaksoptical.com page 31

iOptron www.ioptron.com page 27

Quantum Scientific Imaging www.qsimaging.com page 24

Jack’s Astro Accessories www.waningmoonii.com page 62

Backyard Observatories www.backyardobservatories.com page 18, 19

Rigel Systems www.rigelsys.com page 25

JMI Telescopes www.jmitelescopes.com page 20

Rubylith www.astro-rubylith.com page 17

Vixen Optics www.vixenoptics.com page 3

The Binoscope Company www.binoscope.com page 39

Kendrick Astro Instruments www.kendrickastro.com page 42

ScopeBuggy www.scopebuggy.com page 32

Woodland Hills Telescopes www.whtelescopes.com page 12

Bobs Knobs www.bobsknobs.com page 44

Lumicon www.lumicon.com page 36

Scope City www.scopecity.com page 14

Zeke’s Seats www.zekesseats.com page 33

Astrozap www.astrozap.com page 17

Van Slyke Instruments www.observatory.org page 39

TO ADVERTISE CONTACT advertise@astronomytechnologytoday.com

INDUSTRYNEWS

UPCOMING EVENTS Summer is winding down and, unfortunately, so are the number of stargazing events. As such, this will be the last stargazing events column until spring of 2009. For a list of the remaining events in 2008, visit www.durangoskies.com and navigate the Events Calendar.

Mid-Atlantic Star Party The Mid-Atlantic Star Party takes place October 27 through November 2 east of the community of Robbins, North Carolina. Star and Arrow road signs are placed at intersections within a few miles of MASP to point the way to the site. The MASP location affords views of many deep-sky objects including the Milky Way, some of the southern sky objects, good planetary views as well as great observing of galaxies, nebulae, and star clusters. For details, visit www.masp.org.

Twin Lakes Star Party The 19th Annual Twin Lakes Star Party takes place September 27 thru October 5 at Pennyrile Forest State Park in Kentucky. Pennyrile Forest SP is a prime dark-sky location with broad horizons near a pristine wilderness area and is located approximately 20 miles northwest of Hopkinsville. There will be door prizes, informal talks, and visits to nearby club members’ observatories (by request). For details on this event, visit www.wkaa.net/article.php?articleid=56&cat=SE&ret=index.php.

Deep South Regional Star Gaze The DSRSG, which is the oldest continuously held star party in the south, takes place October 28 through November 2 at Camp Ruth Lee, Louisiana. Camp Ruth Lee, located approximately 45 miles north of Baton Rouge and near the LouisianaMississippi border, is an excellent dark-

sky location with good horizons and a limiting magnitude of about 7.0 at zenith. The weather at the DSRSG in early November is typically very good with average daytime highs in the mid 70s and average nighttime lows in the upper 40s. For more information, visit www.stargazing.net/DSRSG or join the Deep-South-Regional-Star-Gaze Yahoo discussion group.

Eldorado Star Party The Eldorado Star Party takes place October 27 through November 2 on the X-Bar Ranch near Eldorado, Texas.

Sponsored by the Austin Astronomical Society with the support of the Texas Star Party, this event is all about dark sky stargazing in the protected area of the 7,100 acre ranch. And new for this year, you can observe at ESP up to 2 days earlier to enjoy more of the dark skies.

Camping and RV sites will be available for early occupancy, but the registration desk and catered meals will not be open until Wednesday. For more information on this event, visit www.texasstarparty.org/eldorado.html.

All-Arizona Star Party “The monsoon storms are over...

The skies are clearing again... It's getting cooler... It must be time for a big star party!” This is the mantra of AASP, and as a resident of the southwest, I can say that they have summed up the fall weather patterns perfectly. Hosted by the East Valley Astronomy Club, the All-Arizona Star Party takes place Friday, October 25th and Saturday, October 26th at the Farnsworth Ranch. The ranch is located about 30 miles south of Arizona City, which is midway between Phoenix and Tucson. For all the details on AASP, visit www.eastvalleyastronomy.org/aasp.htm.

Nightfall Nightfall is produced by RTMC and is hosted by the Palm Canyon Resort in

Borrego Springs, California. This event takes place October 30 through November 2 and is a great opportunity to bring family and friends to a star party with amenities such as pools, high-speed Internet access, and air-conditioned rooms. Nightfall is unique in that it takes place at a desert resort that cooperates in creating a dark, red light only environment throughout its sprawling property. For more information, visit the Nightfall site at www.rtmcastronomyexpo.org/nightfall.h tm, the Palm Canyon Resort site at www.pcresort.com, or calling (800) 242-0044 and mentioning “astronomy event.”

Astronomy Events is written by Dave Miller. For a complete list, visit www.durangoskies.com and navigate the Events Calendar. To have an event added to the calendar, please contact: events@durangoskies.com.

Telecope Cases & Covers

by Pacific Design

Check Out Our New Soft SC Cases!

Telescope Cases Telescope Covers Tripod Bags Scope Caps Dew Shields

www.casesandcovers.com Astronomy TECHNOLOGY TODAY

11

INDUSTRYNEWS

SKY-WATCHER U.S.A. Synta Optical Technology Establishes U.S. Subsidiary

Super Blowout on Select Meade Products Limited Time!

ETX

LX90 CPS

ACF

LX200 GPS

SkyScout Personal Planetarium Now Just $299!

CGE

Nexstar GPS

Nexstar 8SE

CPC

We are a Coronado Elite Dealer!

P.S.T.

Filters

Get Your Tele Vue 8MM Ethos Eyepiece NOW SHIPPING!

12

Astronomy TECHNOLOGY TODAY

Telescopes

Sky-Watcher 12-inch Collapsible Truss-Dob

The Sky-Watcher brand of astronomical products is well known to those who follow the international telescope market. In fact, Synta Optical Technology, parent of the Sky-Watcher family of companies, is one of the largest manufacturers and distributors of astronomical telescopes in the world. Until recently Sky-Watcher products were not available through dealers in the United States, but that state of affairs is changing.

Synta Optical Technology has established Sky-Watcher U.S.A., a wholly owned subsidiary with its principal offices in Costa Mesa, California. While this new entity is in the process of establishing a network of U.S. dealers for distribution of the Sky-Watcher brands, a growing number of Sky-Watcher products are already available directly from the company’s principal website, www.skywatcherusa.com.

Current offerings include large achromatic and apochromatic refractors, Newtonian and Schmidt Cassegrain telescopes mounted on goto or non-go-to German equatorial mounts, as well as a unique design of quick setup, collapsible truss-Dobsonians. Additional products will be offered as the company expands its operations within the U.S. For more information, please visit www.skywatcherusa.com.

INDUSTRYNEWS

BAADER PLANETARIUM Announce Limited, One-Time Production of Carl Zeiss Abbe II Many consider the Carl Zeiss Abbe Orthoscopics to be among the finest planetary eyepieces ever produced. Unfortunately, they have long been out of production and unavailable. For some years now, Baader Planetarium has worked with Carl Zeiss, Inc., to produce a series of eyepieces that offer the unique characteristics of the original Carl Zeiss Abbe, while taking full advantage of modern design and fabrication techniques.

That project has now resulted in the introduction of the Carl Zeiss Abbe II Orthoscopic Eyepieces, a limited quantity, one-time run of four focal lengths to be sold as sets only. Each Abbe II eyepiece will be fabricated and assembled by Carl Zeiss, Inc., in its Jena optical facility by special arrangement with Baader Planetarium.

The Abbe II eyepieces incorporate glasses of the highest purity and that promise to be the most transparent and colorless that can be produced, into a new lens design that consists of four elements in two groups and that is well corrected on-axis to f/4. Every air-to-glass surface is coated with Zeiss high-efficiency multi-coatings and the eyepieces produce an

14

Astronomy TECHNOLOGY TODAY

apparent field of view of 43 degrees. The Abbe II eyepieces also feature unique Micrometric Field Marks which can be used for accurate centering of objects and for drift measurements.

Each set of Carl Zeiss Abbe II eyepieces includes focal lengths of 4, 6, 10 and 16 mm and are priced at $2390 US. The set is also available with the Carl Zeiss 2x Abbe Barlow for $2790 US. The Abbe II

eyepiece sets are scheduled to begin shipping in October 2008 and are going very quickly. For information on reserving yours, please visit Baader’s U.S. distributor Alpine Astonomical’s Website at www.alpineastro.com.

INDUSTRYNEWS

JMI TELESCOPES Prototyping New Lightbridge Accessories Project

UTA Tabs

In the May 2008 issue, ATT announced that JMI was developing a motor drive retrofit system for Meade’s popular LightBridge series of trussDobsonians. The resulting product has since been named “Train-n-Track” and production units are already being shipped with introductory pricing of $424 US for the 10- and 12-inch, and $449 US for the 16-inch Lightbridge Dobs.

Before it had even begun production of the new Train-n-Track systems, the JMI crew was already at work developing even more LightBridge accessories, including an equipment package that promises to greatly enhance the functionality and portability of Meade’s truss-Dobs. Prototyping is already well underway on the JMI LightBridge “Transporter Kit,” a system that will include holders for convenient

Truss-Rod Holder

Deluxe Counterweight

storage of the three truss-rod pair assemblies, tabs for quickly and simply securing the upper tube assembly (UTA) to the lower tube, and counterweights for counterbalancing heavy accessories that may be added to the focuser or UTA. Two counterweight options are planned: a one-pound (standard version) and a two-pound (deluxe version).

Pricing and the production schedule for the JMI LightBridge Transporter Kits had not been determined as this issue went to press. For more information on these and other innovative JMI products, please visit www.jmitelescopes.com and watch for further announcements in these pages.

"At The Eyepiece" Observing Guides

by Alvin Huey Hickson Group Observer's Guide Abell Planetary Nebulae Observer's Guide Observing the Arp Peculiar Galaxies

www.faintfuzzies.com

BOTH CAMERAS OFFER

Q453-HR – Only $1,499!

The Q453-HR (QHY-8) is a large format 1.8" 6 mega pixel one shot color camera at world beater prices costing less than many competitors’ medium format cameras!

· · · · · · · ·

High resolution / High sensitivity / Excellent Ha sensitivity Full 16 bit analog to digital conversion Extremely low dark current (no dark frames needed if cooling is active) Computer controlled regulated TEC supply (Q285-M only) High speed USB2.0 interface (full frame downloads in less than 10 seconds) High speed focus mode full frame downloads in 1 second Includes Nebulosity for capture (AstroArt and MaximDL drivers available) Sealed CCD chamber with Argon gas purge

www.ccd-labs.com

Q285-M – Only $1,499!

The Q285-M (QHY2-Pro) is a medium format 2/3" 1.4 mega pixel monochrome camera that uses the Sony ICX285AL ExView HAD CCD, the same CCD used in competitors’ cameras that cost as much as $3,000!

Astronomy TECHNOLOGY TODAY

15

INDUSTRYNEWS

EXPLORE SCIENTIFIC Scott W. Roberts Announces Return to Telescope Manufacturing Astronomy outreach enthusiast and former VP of Meade Instruments, Scott W. Roberts, announced his return to the telescope manufacturing industry with the launch of Explore Scientific. The announcement was made during the annual Astronomical League’s Awards Banquet in Des Moines, Iowa, to an amateur astronomer audience that included well-known planetary researchers, astronomy club presidents, active supporters of the Astronomical League, and award recipients who have made major contributions to astronomical science and educational outreach.

Explore Scientific is designing and building telescopes, spotting scopes, binoculars, and microscopes and will engage their customers and the interested public with recognition programs, awards, workshops, and expeditions. The company will also be heavily involved in celebrating the 2009 International Year of Astronomy that was sanctioned by UNESCO and the International Astronomical Union to spread worldwide awareness of astronomy. But the announcement of Explore Scientific comes early as the company will not have products available for market until later this fall.

As to the early timing of the announcement, Roberts explained, “For many years, I exhibited products for and presented awards on behalf of telescope maker Meade Instruments at ALCON, and when the Astronomical League’s President,

16

Astronomy TECHNOLOGY TODAY

Terry Mann, contacted me to let me know that they were looking for a new sponsor for their National Young Astronomer Award, and Leslie C. Peltier Award, I made a commitment on the spot that we would support these venerable programs.

Programs to recognize astronomical achievement by youth and for lifetime contributions in astronomy fit perfectly with the mission of Explore Scientific. So although an announcement in July would be premature, it was important to let the amateur astronomical community know that we are committed to supporting the

causes and recognition programs that are important to them.”

Founded to make astronomy, microscopy, and exploration of nature accessible and affordable, Explore Scientific was organized to help the general public experience the adventure, wonder, and excitement of scientific exploration. The company’s goal is to design, build, and sell products that are high-quality, durable, and a great value.

For more information on Explore Scientific and its growing product lines, please visit www.explorescientific.com, write to explore@explorescientific.com or call 888-599-7597.

INDUSTRYNEWS

PAUL VAN SLYKE AND BLACK FOREST OBSERVATORY A Dream Garage Sale!

Think about it a minute. Whose astrogarage sale would be the most fun – and rewarding? If you’re like us, you enjoy the swap meets that Image 1 break out at various star parties, whether formally or informally. You might even follow the astro-classifieds hoping to score the occasional bargain, sifting through list after list of last generation, massed produced eyepieces, diagonals, focusers, and such. But what if you had the opportunity to be first in line for a chance to buy premium quality, one-off products – things you might not stumble across in a lifetime, much less at periodic star party swap meets or in daily online astro-classifieds.

It’s now been eight years since Paul Van Slyke, owner/operator of Van Slyke Industries Image 2 (VSI), closed his Black Forest Observatory (BFO). As was documented in the May 2008 issue of ATT, BFO’s principal instruments were moved quickly to make room for conversion of the observatory building.

But many boxes of treasures, the likes of which few other than Paul Van Slyke would have had the opportunity to collect, remain tucked away here and there. Fortunately for those of us who know these treasures for what they are,

Paul is finally getting around to completing BFO housecleaning, despite the time demands of the busy and ongoing activities of VSI. A special web page has been established to list the more than 100 items. There you will find huge optical flats, primaries in various stages of completion, and rarest eyepieces, diagonals, turrets, and com- Image 3 ponents of every imaginable description – and all of the quality you would expect of the master designer/fabricator of some of the industry’s most unique and valued products. Plus lots more!

One such item is a unique 2-inch Crayford focuser, Image 1, that is a custom built “one-of-a-kind” for Paul’s unique 10-inch ForkMounted RC Scope shown in Image 2. It has a 12.5-inch long brass moving tube that dou- Image 4 bles as a baffle tube, and a real compression clamp to lock a 2-inch barrel-nose eyepiece or diagonal in place. The redundant smaller knob that is parallel to

the moving tube locks the Crayford focusing shaft. The 4 rpm Hurst synchronous motor is stainless steel spur gear driven (not shown) and has a solenoid engaging mechanism that can be wired to automatically disengage the motor from the focusing shaft for manual focusing. The motor and solenoid both operate on 120vac. You could even plug the motor into a variable frequency drive for speed control.

Another item is the 10-inch diameter 1.7-inch thick first-surface optical flat shown in Image 3. It offers an excellent reflective surface coating with overcoat protection and no chips and was destined for one of Paul’s solar tracking heliostats like the 8-inch shown in Image 4. With this scope Paul used a simple, fixed-position 4-inch achromat lens coupled to a zoom projection lens to project a 6-foot diameter image of the sun on a movie screen inside his observatory for all to see. Paul reports that the real-time, hi-rez white light granulation and sunspots were spectacular and, if you want to go that far, the H-Alpha was even better!

Please visit http://observatory.org/bfosale for photos and descriptions of the items currently offered. You’ll enjoy the visit, even if only window shopping.

Rubylith Saves Your Night Vision!

Rubylith comes in 15×20 inch sheets and can be used to cover anything that emits light. It’s sturdy enough to be reused and flexible enough to cover flashlights, led lights, etc…and of course it’s ideal for computer monitors. It actually increases contrast on monitors for better seeing in the dark!

www.astro-rubylith.com Astronomy TECHNOLOGY TODAY

17

INDUSTRYNEWS

Subscribe Now!!!

ASTRONOMY

TECHNOLOGY TODAY

SIERRA STARS OBSERVATORY Awards Grant to Develop a Software System The Sierra Stars Observatory (SSO) Grant Review Board has accepted a proposal from Fabrizio Tozzi of Italy for a project to develop a software system that is intended to more efficiently identify main belt asteroids, which even now are frequently simply marked as “unidentified” and subsequently “lost” again without sufficient analysis to help link them to other observations of “unknown” asteroids.

The grant will provide significant access to Tozzi for utilizing the SSO to test his software and prove its efficiency and effectiveness. He has been a regular user of SSO for his ongoing asteroid search and recovery projects since its inception.

The Sierra Stars Observatory, featured in the cover story of the December 2007 issue of ATT, is a completely automated robotic observatory.

Talon, its Linux-based observatory control software, sends instructions and monitors the status of the telescope, camera, filter wheel, and dome continually throughout an entire observing session.

D O B S E R VAT O R Y

Our newest offering, the Dobservatory is specifically designed for the low pivot point of DOBs allowing you to view near the horizon. The Dobservatory is available in sizes from 7'6" x 7'6" to 15'6" x 15'6".

The telescope, CCD camera, instruments, weather monitors, and dome work together seamlessly in a fully integrated systems. Unlike most robotic telescope systems that are primarily based upon accessing and controlling the telescopes directly over the Internet, an approach that is rewarding for the user, giving the feeling of actually operating the telescope, but that can also result in inefficient allocation of limited imaging time, SSO users select targets and exposure parameters and Talon creates and schedules a job run, then downloads resulting images after they are taken. Each scheduled object is imaged as close to transit as possible and the user pays only for the actual time the camera shutter is open.

SSO wishes to take the opportunity of the grant to Fabrizio Tozzi to remind readers of its ongoing grant program and to encourage applications for suitable projects.

For more information on SSO’s grant process and services, please visit www.sierrastars.com.

The Home Model is the perfect design of form, function and, of course, pricing with every feature you’ll need for the ultimate in observing! The Home Model is available in sizes from 7'6" x 7'6" to 15'6" x 15'6".

HOME MODEL

From Maine to California, Montana to Texas, BYO builds the highest quality roll-off roof observatories on the market today. We are now beginning our 6th year of providing turn key observatory solutions throughout the U.S. and have gained experience second to none.

Why Backyard Observatories?

ROCHESTER INSTITUTE OF TECHNOLOGY New Astrophysical Sciences and Technology Doctorate Blends Theory, Observation and Instrumentation This fall the Rochester Institute of Technology will launch its fifth doctoral program in Astrophysical Sciences and Technology. The new Astrophysical Sciences and Technology Doctorate at RIT blends theory, observation and instrumentation into one program.

The new program brings together scientists from different disciplines within RIT’s College of Science to explore Einstein’s theory of relativity, young and dying stars, centers of galaxies and black holes, and the technology to make new observations.

The program will depart from traditional astrophysical studies that focus mainly on theoretical and observational aspects of the discipline by adding technology and applied science. An equal emphasis on theory, observational astronomy, and sensor and instrument development will set RIT’s program apart from others.

Students will have the opportunity to earn master’s and doctoral degrees in three distinct tracks: the emerging field of astro-informatics and computational astrophysics; astronomical instru-

mentation and the development of new technologies for application in astronomy and space science; and astrophysics.

The program will draw heavily upon faculty from RIT’s Chester F. Carlson Center for Imaging Science, Department of Physics and School for Mathematical Sciences who are international experts in the areas of extragalactic astronomy, particularly the study of the centers of galaxies and stellar evolution, computational astronomy and numerical relativity, and instrumentation.

The Rochester Institute of Technology faculty will stimulate cutting-edge research opportunities for students at the graduate and undergraduate level at RIT, engaging them in the development of new technologies, modeling with state-of-theart computers, observing with telescopes, all geared toward probing our universe, and developing a deeper understanding of the evolution of the objects, forces and energy that comprise them.

For more information about the Rochester Institute of Technology’s new programs go to www.rit.edu.

CLUB MODEL

Our Club Model is quite probably the largest home observatory available and more bang for the buck than anything else out there! The Club Model is available in sizes from 16' x 20' to a whopping 24' x 32'!

WWW.BACKYARDOBSERVATORIES.COM • 330-667-3214 WWW.M1OASYS.COM

More options, Most roll-off roof experience, 25 years construction experience, Turn-key installation, Ever customizable designs, Highest quality residential specs (not shed type construction), Heavy duty industrial capacity roller system design, Exclusive m1 OASYS roof automation, Standard and Heavy Duty roof motor designs, Big Bear Piers, Warm/Control room options, Plans available created by an experienced builder/astronomer with DIYers in mind, Our observatories have been chosen 10 to 1 over other commercially built observatories at Deerlick Astronomy Village.

BYO EXCLUSIVE

m1 OASYS A Backyard Observatories Exclusive! The m1 OASYS system is the ultimate Roll-OffRoof Observatory Automation/Security System. This very flexible and robust system is a must-have tool for anyone wishing to secure, monitor, and remotely control their telescope observatory and best of all, you can install it yourself! Go to www.m1oasys.com for more info.

Factory authorized sales and installations of Technical Innovations’ Home Dome, Pro Dome and other fine observatory products.

FACTORY INSTALLATIONS

BACKYARD OBSERVATORIES

NEWPRODUCTS

WILLIAM OPTICS Introduces A Variety Of Products William Optics has introduced several new products for this fall including its long awaited addition to the FLT triplet series of high-performance apos. The FLT-98 (Image 1) combines exceptional optical and mechanical quality with a highly useful aperture and focal ratio to produce what promises to be not only an exceptional visual tool, but also an ideal platform for breathtaking astro-images.

The top-quality triplet air-spaced objective is simply among the finest William Optics has ever produced – extremely sharp, with the optimum color correction that is ideal for astrophotography.

The objective was designed by a leading Russian engineer and features FPL-53 glass and each precision optical element is fully multi-coated using William Optics’ proprietary SMC coatings.

The lightweight pure carbon-fiber tube and dew shield yield an assembly that is perfectly enhanced by contrasting anodized components – pure William Optics quality fit and finish. The dew shield is retractable.

The extra-smooth, 2.5-inch LinearPower focuser is designed specifically to meet the most rigorous demands of astrophotography and features a two-speed micro-focuser with large knobs and graduated scale for precise camera alignment. The entire focuser assembly is 360 degree rotatable.

For best protection of its superior finish, the FLT-98 is delivered in a practical and safe custom aluminum case and premium mount rings and a 1.25-inch adapter are also provided. A dedicated field-flattener is available as well.

It features aperture of 98 mm, f/6.3 focal ratio, and focal length of 618 mm. The focuser offers 2.5-inch (63.5-mm) clear aperture, 1:10 fine focus, and 80 mm focus travel. The tube length is 505 mm (fully retracted) and 600 mm (fully extended) and the tube weight is 7.7 pounds (3.5 kg).

The newest Megrez series apo is an 88-mm beauty appointed in an elegant William Optics signature white, precision CNC machined tube with gold-anodized objective cover and fine-focus knob.

The Megrez 88 (Image 2) features an FD air-spaced doublet objective that is f/5.6 fast, producing a valuable alternative to the longer focal length Megrez 90FD. A dual-speed, fully

rotatable 2-inch Crayford focuser is also standard and the dew shield is retractable. The tube assembly of the Megrez 88 includes an L-type mounting bracket that is threaded to accommodate a standard camera tripod.

It features 88-mm aperture, a focal ratio of f/5.6 and focal length of 498 mm. The focuser offers 2-inch (50.8-mm) clear aperture, 1:10 fine focus, and 80 mm focus tube travel. The tube length is 397 mm (fully retracted) and 488 mm (fully extended) and the tube weight is 7.5 pounds (3.4 kg).

The new William Optics 70-mm ED Doublet ZenithStar (Image 3) operates at f/6.2 and is a true multi-purpose tube assembly with excellent mechanics, Crayford 2-speed fine focuser, and super-high transmission multi-coatings. Its fast focal ratio and compact dimensions make for an ideal fast set-up astrophotography, piggybacking or spotting scope.

The lens design features Japanese Ohara, FPL51 (ED) glass to create the doublet air-spaced objective that rests in a CNC machined, ultra-high precision lens cell. Each lens element is fully multi-coated with a special super-high transmission coating (STM Coating) on all surfaces. The tube is fully baffled to block all extraneous off-axis light rays and prevent glancing reflections, increasing overall contrast.

The ZenithStar 70ED is a perfect match for William Optics’ EAZY-T Alt-Azimuth mount.

You can even slide it directly into the mount without a mounting plate if you like. The OTA features a retractable dew shield and fully-rotatable Crayford focuser with adjustable focus tension and super-smooth 1:10 micro-focuser for finest adjustment during imaging sessions and visual observations alike.

The aperture is 70 mm, focal ratio is f/6.2, and the focal length is 430 mm. The focuser is a 2-inch (50.8-mm) clear aperture Crayford with 1:10 Dual Speed Micro Focuser and 81-mm (3.2-inch) focus tube travel.

The new William Optics 22x70 Apo Binoculars (Image 4) have been designed specifically with excellent color correction in mind, a must for optimum performance of high-magnification astronomical binoculars. Each 70-mm airspaced doublet objective features premium FPL051, extra-low dispersion glass and produces

Image 1

Image 2

Image 3

Image 4

extremely bright, sharp images from edge to edge.

For the mechanical design, William Optics opted for the enhanced rigidity of individual eyepiece focusing, with a dioptric range of +5 to -5. All air-to-glass surfaces of the objective, Porro prism, and 66-degree eyepieces are fully multi-coated and the binoculars are guaranteed to be waterproof. The design also features retractable dew shields and the twin barrels are cross reinforced to a central bar that includes a sliding mounting post. The introductory price for the new WO 22x70 Apo Binoculars is $849 US. For more information on these new William Optics products, please visit www.williamoptics.com.

Astronomy TECHNOLOGY TODAY

21

NEWPRODUCTS

CATSEYE COLLIMATION/WOOD WONDERS Offers New Fieldcase Designs

Catseye Collimation and its partner, Wood Wonders, have introduced another new fieldcase design, “The Celestial Fieldcase.” This unique, solid-Oak fieldcase is decorated on four sides with 3D celestial carvings and is the ultimate in storage and display of your prized eyepieces and other observing accessories.

22

Astronomy TECHNOLOGY TODAY

It has a Red LED lighting system, with on/off-brightness control, that is activated upon opening the lid. With pull-out drawers on both sides, ample storage underneath, and a flip-down Plexiglas storage partition in the lid, there is plenty of room for all your observing essentials. The eyepiece layout can be

customized to match your specific collection or you can choose from four standard layouts. And, you can also choose a stain option for a custom look. “The Celestial Fieldcase” design is an eye-catcher at star parties and a must have for the serious enthusiast.

The dimensions of the case are 20 inches (W) x 10 inches (D) x 8.5 inches (H) and it weighs 11 lbs. The upper storage is 4-3/4 inches x 8-1/4 inches x 2 inches and the lower storage compartments are 5 inches x 9 inches x 2-3/4 inches. It features solid Oak with brass hardware. It offers hinged Plexiglas inside of lid for reference material and side drawers pull out for additional room underneath. It can be configured in a standard eyepiece layout, however custom holes and spacing are available on request. The standard price for “The Celestial Fieldcase” is $349 US, and the stain option is an additional $35.

Another new offering from the team is a smaller, more compact, “Eyepiece Case.” This case actually has more room for eyepieces than the standard fieldcase, but without the additional storage of the pull-out drawers. They have the same red lighting and dimmer on/off system, and also have the Plexiglas storage partition in the lid. In addition to a similar “Celestial” design, there is also a “Shooting Star” and “Standard” model without carvings.

These Eyepiece Cases provide another eye-popping show stopper for storage and display of your prized eyepieces For more information on these products, please visit www.catseyecollimation.com.

NEWPRODUCTS

ORION TELESCOPES & BINOCULARS Introduces Several New Products Among the many new products recently heating bands (sold separately). The conintroduced by Orion Telescopes & Binoculars troller’s microprocessor-controlled circuitry is a 190-mm f/5.3 Maksutov-Newtonian delivers pulse-width modulation for stable, (Image 1) that is targeted at serious astrophoprecise temperature control. Each heater outtographers who demand large-aperture, flatput features its own temperature control field, coma-free performance. That the 190 knob with adjustments from zero to 100 Mak-Newt is also affordably priced is an added percent. bonus.

The individual heating bands are powerThe scope’s primary mirror is fashioned efficient, drawing only 0.25 amps to 2.8 amps from low-expansion Pyrex, while its meniscus at maximum output. Five different heating lens is from fully multi-coated BK7 Schott band sizes are available and each comes with a glass. The optical train is designed to produce 6-foot cable that plugs into the control module pin-point stars from center to edge of the large via an RCA-type connector. Removable caps sensors of popular CCD and DSLR cameras. are included to protect any unused ports from The mechanical design exposure to the elements and the and construction of the 190 control module also has an auxilMak-Newt is in keeping with its iary 12-volt port, which allows optical excellence. The 37.5-inch you to power any 12-volt accessosteel tube has thick 1.5-mm walls ry directly from the module. to provide the rigidity necessary The Dew Zapper Pro conto maintain critical collimatrol module is powered tion, even when loaded by a 12-volt field battery, with heavy imaging trains, such as the Orion’s and its precision machined Dynamo Pro, and comes aluminum Crayford focuser with a car lighter-style provides smooth, accurate, DC plug on a 12' firm positioning of those cable. The Orion Dew Image 2 imaging components. The Zapper Pro 4-Channel optical tube features five knife-edge baffles to Control Module is currently priced at just eliminate internal reflection and insure excep$109.95 US. tional contrast.

The popularity of ultra- Image 3 Although the Orion 190 Mak-Newt was portable telescopes and mounts is designed with astro imaging in mind, it is at an all time high and we’ve equally competent with an eyepiece in the never enjoyed more focuser and an included extension adapter options, which is good insures that a wide variety of eyepiece designs news for those of us will reach focus with the scope. who’ve long wished for a The Orion 190 Mak-Newt is sold as an truly “backpackable” teleoptical tube only and is currently offered at an scope/mount combinaintroductory price of just $1299.95 US. tion. But, while we’ve Orion’s new Dew Zapper Pro 4-Channel searched for the perfect Control Module (Image 2) is designed to backpack scope, it may be serve as an integral component of the larger that what was really lackDew Zapper Pro 4-Channel Dew Prevention ing was the perfect teleSystem. This advanced dew prevention system scope backpack and Orion’s independently powers up to four individual new Observer’s Backpack Case has

Image 1

the potential of providing just that.

The Observer’s Backpack Case (Image 3) offers room and compartments to carry your entire telescope setup comfortably on your back, while keeping all of your gear organized and protected. Specially designed for amateur astronomers, this fully padded, backpack-style case can hold up to an 8-inch Cassegrain or a 4-inch short-tube refractor, plus a small mount, tripod, and accessories. The main telescope compartment has customizable padded dividers – there’s even a padded pouch for a laptop computer – and a separate compartment contains variously sized mesh pockets for small accessories. On the outside are an expandable front pocket, buckle straps for a tripod, a water bottle pouch, and a carrying handle.

Strap it on and you’ll notice that the thickly padded shoulder straps and waist belt provide excellent comfort and weight distribution. Now few dark sites are too remote for your favorite portable telescope and mount.

The internal dimensions of the main compartment of the case measure 23 inches long by 14.5 inches wide by 7 inches tall and it is priced at $129.95 US. For more information about these Orion products, please visit www.telescope.com.

Astronomy TECHNOLOGY TODAY

23

NEWPRODUCTS

BAADER PLANETARIUM New LRGBC Anti-Reflection Filters Baader Planetarium’s new luminance, red, green, blue, and clear focusing (LRGBC) filters with anti-reflection coatings are designed to deliver improved color saturation and image quality – improvements that Baader cautions may be so dramatic, they may actually “cause many astro-imagers to re-take images of their favorite objects.”

As to what makes the new filters so special, Bob Luffel of Alpine Astronomical explains, “Their ultra-steep cutoffs and high transmission (>95%) allowed Baader to effectively separate the important H-Beta and O-III lines. The Baader Blue filter passes virtually all of the H-Beta and O-III lines, while the Green filter is able to capture all of the O-III line, without encroaching into the HBeta line. None of the light is wasted by either filter. In this way, O-III is represented as it should be, a teal (blue-green) color, and H-Beta is captured solely in the blue. Rarely has this degree of separation been achieved, and with such high transmission of both lines.”

Luffel continued, “In addition, the Green and Red filter passbands nearly touch, leaving

only a sharp notch to block out the primary Mercury/Sodium light pollution line at 580nm. The high transmission everywhere else delivers the shortest combined exposures possible.”

The coatings applied to these filters were also designed to eliminate the annoying reflections that can make some astrofilters difficult to use. Achieving this degree of antireflection properties required a careful balancing of the coating stacks made possible only by extensive

testing. The high optical quality of the filters insures that there is no loss of sharpness or contrast. Baader LRGB filter sets and C-filters are available in four sizes, standard mounted 1-inch, 2-inch, as well as 50.8-mm diameter round and 50-mm square bare substrates (unmounted) for use in larger format cameras.

For pricing and additional information on the unique performance and features of these filters, please visit www.alpineastro.com.

Astronomy TECHNOLOGY TODAY

25

NEWPRODUCTS

SEAPORT DIGITAL i-Visor Laptop Case Gains Popularity with Astronomers While Seaport Digital’s products have been enjoyed by laptop users for some time now, its i-Visor laptop cases are just now being discovered by astronomy enthusiasts who find that the i-Visor cases provide the perfect solution to the challenges they face as laptop computers are added to the list of standard telescope accessories.

When closed, the i-Visor looks like a standard padded laptop case constructed of rugged ballistic outer fabric.

But i-Visor cases offer a hidden feature that is of peculiar utility to field astronomers – they open to reveal a patented tri-fold visor that unfolds to provide a shield for the enclosed laptop while it is in use. The iVisor was originally designed to shield sen-

sitive data from view of curious fellow passengers as laptop users worked while traveling on crowded public transit systems. It was soon discovered however by professionals who routinely use laptops in too bright indoor and outdoor conditions and who nevertheless require access to the highest quality image from their laptop screens.

The i-Visor serves astronomers by insuring that only the user seated immediately in front of the laptop is exposed to the light emitted by its screen. We’ve all suffered the inconvenience at one time or

another of having our critical dark adaptation diminished by the glow of laptop screens, even those of owners who thoughtfully cover them with red film. Now there’s an even better solution to this growing problem.

Astronomers are also discovering that the padded tri-fold visor provides effective dew prevention for laptops otherwise used under open skies, all the while protecting expensive laptops from those of us who too often bump into our sensitive equipment in the dark. i-Visor cases are available in sizes that will accommodate most popular laptops and are priced from $69.99 US. For more information, please visit www.seaportdigital.com.

JMI TELESCOPES New Configurable Carry Case

Parabolic & Spherical optics Elliptical Diagonal Flats Complete interferometric data 27 years (full-time) experience

www.ostahowskioptics.com fineoptics@dishmail.net 951-763-5959

Telescope Accessories & Hardware FEATURING ITEMS FROM:

TeleGizmos Covers - Astrozap Dew Shields Dew-Not Dew Heaters - Peterson Engineering Antares - Telrad - Rigel Systems - Sky Spot Starbound Chairs - Smart Astronomy David Chandler - Lightwedge - Baader ScopeStuff Piggyback & Balance Kits Rings, Rails, Dovetails, Cables, ATM, Eyepieces, Filters, Diagonals, Adapters Green Lasers - And MUCH more!

www.scopestuff.com 512-259-9778

26

Astronomy TECHNOLOGY TODAY

JMI has added yet another option for the safe transport of your valuable astro-gear. Its new 19-inch configurable carry case can be easily configured by the user to custom fit a host of telescopes, including Celestron’s C8-S, C8SGT, CGE 800, G-8, GP C8, NexStar 4, 4 GT, 4i, 4 SE, 5, 5i, 5 SE, 6 SE, and SP C8, Meade’s ETX-90, ETX-90EC, ETX-90PE, ETX-105EC, ETX-105PE, ETX-125EC, ETX-125PE, GEM 2080, LXD55 SC-8, and LXD75 SC-8, and other 8-inch SCT optical tube assemblies.

The case includes a foam lining with inside dimensions of 19 inches by 11.5 inches by 9 inches, plus configurable foam flat spacers and blocks. Some of the blocks feature 1.25-inch round holes for holding eyepieces, diagonals, and the like, and glue is included for permanent placement of the configurable foam

pieces to securely hold the scope or other equipment that the user chooses to store.

Each case includes one steel-reinforced handle, two lockable latches, and a 2inch by 20-inch durable steel hinge.

The outside dimensions of the case are 22.75 inches by 16 inches by 11 inches, it weighs 8.8 pounds empty (shipping weight is approximately 13 pounds), and it is priced at $169 US. For more information, please visit www.jmitelescopes.com.

Vixen VMC200L Mak-Cass and SXD Sphinx Deluxe Equatorial Mount The VMC200L and Vixen SXD mount are shown assembled at Yosemite National Park ready for a night of viewing.

By Erik Wilcox

Vixen VMC200L Mak-Cass When it comes to buying new gear, amateur astronomers are usually a very analytical group. We research options, compare specs and reviews, and try and make an informed decision. In the end, we consider all the tradeoffs, and choose the gear that best fits our needs.

That doesn’t necessarily mean “the perfect scope,” just the best one available given our individual set of parameters. Some of the clichéd sayings, such as “There’s no free lunch,” and “You can’t have your cake and eat it too,” come to mind here.

With telescopes, aperture and portability are often strong considerations. For that reason, many choose 8- to 10-inch Schmidt Cassegrain (SCT) designs. However, the long delays SCTs often require to reach thermal equilibrium

(particularly when going from a warm house to a cold backyard) partially negates their portability advantage for “quick looks.” But what if there were an equally compact and lightweight scope that cooled down quickly and offered 8 inches of aperture? Additionally, what if this scope didn’t use the front-mounted corrector plate that is so famously susceptible to dewing and didn’t suffer from image shift during focus as many SCTs often do? Well, if that sounds appealing, the Vixen VMC200L may be the scope for you.

First, the specs: the VMC200L is a 200mm aperture Meniscus Catadioptric System, a Mak-Newt. It employs an interesting design, using an f/2.5 spherical primary mirror and a meniscus corrector element located between the secondary and primary mirrors. This gives the scope a working focal ratio of f/9.75. Instead of a front-mounted corrector plate, the secondary mirror and corrector element are

held securely in place by a sturdy 4-vane spider.

A smooth rack and pinion focuser moves a focus drawtube, not the mirror, so there is no image shift during focus. And, the whole optical tube assembly (OTA) weighs only 13 pounds!

I received the OTA in a well-packed box and the scope arrived in perfect collimation.

How often does that happen? In the event the scope had needed to be collimated, there are adjustments for both the primary and secondary, but because the optics didn’t need realigning, I resisted experimenting with any adjustments.

One of the first things that caught my eye was the sturdy metal handle positioned on top of the OTA. This makes moving and transporting the OTA so much easier and makes me wonder why we don’t see similar handles on telescopes from other manufacturers. The handle is equipped with a standard 1/4-20 mounting Astronomy TECHNOLOGY TODAY

29

VIXEN VMC200L AND SXD SPHINX DELUXE MOUNT Park for a weekend of darksky observing, but as luck would have it, nearby fires smoked out the skies both nights we were there (luckily, firefighters later extinguished the blaze, so the park was spared any damage). So, aside from a couple of quick looks between clouds over the next week, and visually admiring the scope, observing had to wait. The next weekend I brought the scope to Fremont Peak Observatory for the annual “Star-B-Q” event held there, and finally enjoyed those clear, dark(ish) skies I’d been waiting for!

The first object I pointed the scope towards was Jupiter, since it was prominent in the southeast as darkness fell.

Right away, I was able to appreciate the fast cool down of the optics. Within 30 minutes A look into the open end of the VMC200L OTA reveals well-blackened surfaces and a rigid assembly that holds after taking the scope out of rock-solid collimation my warm vehicle, I was viewing the gas giant at 244x with bolt, so an additional accessory can easily be a Tele Vue 8-mm Ethos. There was a lot of piggybacked directly on top of the OTA. The banding detail and Jupiter’s moons were tiny VMC200L also comes with a nice illuminateddiscs. The bands showed a subtle amount of reticle 7x50 finderscope with a handy, twist-up color and several festoons were clearly visible as eyeguard to properly position the eye. A 1.25well. Despite the 40-percent central obstrucinch mirror diagonal with a built-in flip mirtion formed by the secondary mirror assembly, ror is standard equipment as well. contrast was very good. Additionally, the I brought this scope, together with a Vixen straight secondary spider mount didn’t produce Sphinx Deluxe Mount, to Yosemite National the objectionable diffraction spikes that I had

Get Yours Today!

Let us custom build you the best, strongest, most well constructed scope transport case available!

www.scopeguard.com

anticipated, even on bright objects like Jupiter.

I could see the spikes if I really looked for them, but they weren’t intrusive at all – and that’s coming from a guy who has installed curved spiders in every Newtonian he’s ever owned!

On deep sky objects, the scope performed admirably. I had forgotten to bring a 2-inch diagonal along, but with a 2-inch extension tube, I was able to get a William Optics 28-mm UWAN to come to focus for a wide 71x. Suddenly, I was swimming through Sagittarius! Star fields were just beautiful, with edge-to-edge sharpness, and all of the showpiece objects looked decidedly impressive through the VMC. While swapping out eyepieces and comparing the views, I did notice that the supplied flip mirror diagonal seemed to degrade the image a bit. This was seen especially on Jupiter at high power and several others at the star party confirmed my impression. The flip mirror seemed to add its own false color, as one side of Jupiter showed a bluish tinge that wasn’t present otherwise. I didn’t care much for the “flip” mechanism either, as there is no click stop. The knob used to flip the diagonal is simply turned until it stops. When viewing, it’s easy for the knob to get moved a bit, which would obviously tilt the diagonal mirror at an angle that wouldn’t be optimum. I’d also like to see compression rings to secure eyepieces, instead of setscrews, but that is just my personal taste – not everyone likes them.

Over the next few days, I was able to get the scope under the stars a bit more and found myself enjoying all that the V MC200L had to offer. It provides a lot of aperture in a small, durable package, and the scope is very easy to use. I checked the collimation again after using

True 360 Degree Rotating Pier Plate for AP 900 and AP 1200 Mounts!

Only $275 for the 900 and $325 for the 1200 – Shipping included Continental U.S!

www.malcoprecision.com 30 Astronomy TECHNOLOGY TODAY

VIXEN VMC200L AND SXD SPHINX DELUXE MOUNT

OFFERS: SOLAR FILTERS • H ALPHA ECLIPSE VIEWERS • R-G SOLAR FILM DEW HEATERS • NEBULA FILTERS www.ThousandOaksOptical.com The VMC features a catadioptric “Field Maksutov” design with spherical primary and secondary mirrors and a meniscus corrector element positioned between the secondary and primary mirrors. The secondary mirror/meniscus assembly is rigidly suspended by four stout spider vanes. Focus is achieved by a rack and pinion focuser mounted to the rear visual back of the scope. The primary and secondary mirrors remain stationary to eliminate image shift during focus.

the scope for several days and was happy to see that it held alignment well, despite being transported and set up several times.

Optically, there’s nothing to complain about. I saw no edge-of-field problems at all and images were crisp and well defined through

the eyepiece. The f/9.75 focal ratio is noticeably faster than the typical Maksutov design and, of course, that translates into a wider true field of view with any given eyepiece. Reaching focus is easy, as there is a nice, sharp “sweet spot,” and there is never any doubt when you’ve

VIXEN VMC200L SPECIFICATIONS AND FEATURES Aperture ..............................................................................8-inches (200 mm) Focal Ratio ..........................................................................................f/9.75 Focal Length....................................................................76.8 inches (1950 mm) Primary Mirror Focal Ratio .........................................................................f/2.5 Primary Mirror Focal Length ..................................................19.7 inches (500 mm) Secondary Mirror Diameter ....................................................2.8 inches (71.1 mm) Secondary Obstruction .......................................3.1 inches (80 mm), 40% of aperture Distance from Primary to Secondary .........................................~ 13 inches (330 mm) Optical Tube Dimensions.........................................9.1 x 21.1 inches (232 x 535 mm) Total Weight...............................................................................13 lbs (5.9 kg) Focuser Type ...................................................................2-inch Rack and Pinion

Astronomy TECHNOLOGY TODAY

31

VIXEN VMC200L AND SXD SPHINX DELUXE MOUNT hit it. I felt this was important, given that the rack and pinion focuser is not currently available with a dual speed option. I should note though that JMI now offers an adapter for equipping the VMC200L with its new Event Horizon Crayford focuser for those who prefer that design, but I found nothing to dislike about the standard rack and pinion unit with which the scope was equipped.

Another thing I noticed was that the Vixen attracts attention. At the Star-B-Q event, attendees stopped by frequently and asked questions about it. They were very interested in the scope and very impressed after viewing through it. The large, red Vixen logo prominently displayed on the OTA gives the scope an air of superiority, and the build quality and performance lives up to its looks. The glossy white finish is durable and nice to look at, and the scope is solid throughout. The flip mirror is, in my opinion, something that could be improved on, but as it is a removable accessory, it’s not really an issue. Overall, this is just a really nice, well performing telescope, and a very unique one at that. Lightweight, portable, 8 inches of aperture, fast cool down, zero image

shift, and reasonably priced – I guess it may be possible to have your cake and eat it too after all!

The Vixen SXD Equatorial Mount The Vixen Sphinx mounts have been available for a few years now and are recognized as a very solid and capable platform for the serious observer and astrophotographer alike.

However, with the release of the new SXD (Sphinx Deluxe) version of the mount, Vixen is again pushing the boundaries of innovation and quality.

Cosmetically, the SXD mount looks nearly identical to the SX mount, aside from a more classic black and white logo (as opposed to the flashier translucent blue of the SX).

However, internally the SXD is definitely in another league altogether. It features one-piece hardened steel RA and DEC shafts with needle bearings, 180-tooth brass worm gears, and a gross load capacity of 50 pounds (including counterweights). Yes, that’s right, 50 pounds!

ScopeBuggy MAKING VIEWING EASIER! • • • • • • • • •

For use with most tripods, DOBs and piers Load tested to 600+ pounds Assemble in minutes for use or storage Pneumatic inflated 10” tires for soft ride Gloss Black powder coat paint Optional battery equipment tray Approx.

Adjustable rear axle height, 1 1/2” to 7” Plus S&H, g USA pin $30 Shipei Anodized gold wheels ght 36 lbs.

Shipping w ground PS One person can move any size scope U shipped quickly and easily • Ideal for the new Meade RCX Series • Ideal for the Meade LightBridge Series Patent Pending • Ideal for scopes up to 36”

$

SCOPEBUGGY P. O. Box 834 Elephant Butte, NM 87935

Please visit us at www.scopebuggy.com

Toll Free: 866-312-8449

295

WE ACCEPT: VISA – MASTERCARD – AMERICAN EXPRESS PAYPAL – MONEY ORDERS – CASHIERS CHECKS

32 Astronomy TECHNOLOGY TODAY

Additionally, all of the features people have come to appreciate in the SX mount are included: the innovative Star Book controller, goto capability with a 22,000 target object database, periodic error correction (PEC), and the very nice SX polar finder scope.

The equatorial head is truly a work of art; everything is solid and of highest quality. Like the Star Book, there are some innovative features here as well. The counterweight shaft slides into the body of the equatorial head, which makes it more portable for transport.

Additionally, the design of the front portion of the head is well thought out. It appears that Vixen placed much of the weight in the section near the counterweight shaft, enabling the user to achieve balance with fewer counterweights.

Consequently, I found that the 8-pound weight, the larger of the two supplied with the scope, was sufficient for countering the VMC200L and the accessories it carried. In the control area, there are only two cables necessary for visual use: one for power and one for the Star Book. A standard Vixen dovetail plate makes mounting almost any scope a possibility.

The SXD that I tested was equipped with Vixen’s renowned HAL-130 tripod and the legs of that tripod are deceptively solid. While they are made of aluminum, they don’t at all resemble the flimsy legs used on many entry level mounts. Unlike those designs, the HAL-130 doesn’t use the standard square-tube leg design that loses stability as the tripod is extended. Instead, one section of each leg of the HAL-130 fits entirely inside of the other, and both are formed in a solid, one piece design. They’re made of thick aluminum, so there are no weak parts to sacrifice stability. Best of all, they’re much lighter in weight than the standard tubesteel fare, but not so light in weight that the mount is top heavy. With the eyepiece tray attached, I found the tripod/mount assembly to be very solid, with dampening times well under two seconds. With the 8-inch VMC200L mounted, the SXD hardly knew it was there.

It’s safe to say that the SXD would make an exceptional platform for serious astrophotography.

The Star Book controller is simply a whole lot of fun to use. Its 4.7-inch color LCD display renders controllers with one line of slow mov-

VIXEN VMC200L AND SXD SPHINX DELUXE MOUNT ing text very much things of the past. The detailed star chart makes aiming the scope with the controller very simple; it scrolls along in real time as the scope is being slewed and motor speeds are automatically adjusted in proportion to the field displayed on the screen. The buttons that are used to “zoom” the star field display in or out also control the motor speed. A widefield chart view is typically used to quickly locate the desired area of the sky. Once there, the displayed chart can be “zoomed in” for a closer look. Everything is intuitive and easy to use, and setup is a breeze.

The Star Book can also be used as a standalone star chart, as it has its own power connector (which isn’t used otherwise).

Additionally, it has an autoguider port, and an Ethernet connection for running the mount from a computer. Software updates are available from Vixen Optics and can be downloaded with a PC through the Star Book. New comets can be entered into the database as well.

For standard visual use, only the 9-pin connector that attaches to the equatorial head is necessary; no tangled cords here. The only remotely negative thing I could say about the Star Book is that at times I wished it was more ergonomically designed to fit my hands. Because of its large screen, the controller is also physically large, and the big square shape might be improved upon. But again, the physical size of the controller is necessary to house the large 4.7-inch screen, which in turn is essential to showing the level of detail of which the Star Book charts are capable.

Upon turning the unit on for the first time, the language must be set, as Japanese is the default. Luckily, the word “language” on the startup screen is in English, so setting the displayed language to English wasn’t at all difficult. For future use, all settings of the Star Book can be saved, as well as the “Home Position” of the telescope (if it’s in a permanent location or won’t be moved far before the next observing session). After entering local time and location, the alignment procedure may be started. First, in Chart mode, the scope is pointed at the western horizon (the Star Book asks you to point the mount at the “right” horizon, which could be confusing, depending on where you’re standing relative to the mount).

This cutaway view of the Vixen Sphinx SXD Mount indicates the locations of the 5 needle bearings with red ovals. The mount achieves greater carry capacity by incorporating one-piece hardened-steel RA and Dec shafts and needle bearings throughout.

VIXEN SXD EQUATORIAL MOUNT SPECIFICATIONS AND FEATURES Weight is 19.4 lbs (8.8 kg) Without Counterweights Gross Mount Capacity Including Counterweights is 50 lbs (22.7 kg) Steel RA and DEC Shaft 5 Sets of Needle Bearings 180 Tooth Brass Worm Gear in Both Axes Interactive Star Book with 4.7-inch Color Display Full Go-To Capability to 22,000+ Objects Upgradeable Firmware and Comet Database Universal Vixen GP Dovetail Receiver One 4.2 lb (1.9 kg) and One 8.2 lb (3.7 kg) Counterweight

Our astro seats are hand TIG welded from aircraft quality aluminum to last a lifetime.

Great Seat–Great Price.

Four full inches of foam padding for all night comfort.

One handed adjustment from 0' to 33" Weight approx. 10 lbs.

Only $119.00

Zekes Seats

Made in USA

The Sky Looks So Sweet, If You

GET A ZEKE SEAT!!

17611 East Street • North Fort Myers, Florida • (239)995-9353

zekesseats.com

Astronomy TECHNOLOGY TODAY

33

VIXEN VMC200L AND SXD SPHINX DELUXE MOUNT After doing this, the scope can then be aligned with a couple of bright stars. I found that three stars were more than sufficient for accurate goto performance, though more stars can be chosen if an even higher level of pointing accuracy is desired.

After setting everything up the first time, I realized that the mount I received for review was only equipped with a 120-volt AC wall plug. However, a quick trip to Radio Shack solved that problem. The DC connection is 12 volt and, though the input plug that fits directly into the mount wasn’t available at the electronics store, the Vixen AC power supply (which has a short, detachable section) has a more common jack. That input plug was available, so I used that portion from the Vixen AC power supply. I connected the new plug to that jack, so I could use a DC cigarette lighter plug and my DC power tank. This worked just fine.

Under the stars, I quickly got accustomed to using the Star Book and rarely needed the manual for assistance. Basically, there’s a “Chart Mode,” which is used during setup and to search for objects to “go-to,” and a “Scope

34 Astronomy TECHNOLOGY TODAY

Mode,” where the star chart is synched with the telescope. In Scope Mode, as you slew the telescope, the star chart moves to accurately reflect where the scope is being pointed in the sky, or vice versa. Unlike many other systems I’ve used, I never experienced any errors, frozen screens, or other “bugs.”

The Star Book and mount simply worked smoothly and flawlessly – every time.

And go-to performance with the SXD was impressive.

With a simple polar and 3-star alignment, the mount placed the desired object in the field of view of a 24-mm Panoptic every time.

And unlike many other mounts of similar capacity, the SXD mount doesn’t sound like a broken coffee grinder when slewing. It’s fairly quiet, even at maximum speed, with an efficient sounding

low whine as it moves across the sky. When tracking, there’s a detectible clicking sound, but again, it’s not at all noisy or distracting. I doubt there would be much of a problem using this mount in an urban area with neighbors sleeping nearby.

There are lots of other interesting features and discussing all of them would take much more room than is available here. But some of the more important include the periodic error correction (PEC) feature, which allows the mount to “learn” the specific worm gears. The PEC function is used to compensate for any varying machining tolerances, or those that may develop over time, etc.

With a few simple key inputs by the user, the mount can be recoded directly from the Star Book. With the mount I tested, this wasn’t necessary for visual use, as objects remained perfectly “still” in the field of view, even at high power.

Other simple user adjustments, such as backlight brightness and duration, brightness of the polar-alignment scope, volume adjustment from the built-in Star Book speaker, and slewing speed, are all easily accessible. The Star Book is also adjustable for latitude. From the factory, it’s set at a 35-degree “middle latitude,” which gives acceptable results from 20 to 50 degrees, but can be adjusted to use anywhere from 70 degrees North to 70 degrees South.

Overall, I was very impressed with the Vixen SXD mount. It’s an exceptionally solid, well-designed and well-made platform. It’s lighter in weight than many competitive mounts without any sacrifice in stability. This is largely due to the hefty aluminum tripod legs and unique center of gravity design of the equatorial head. And the Star Book is an amazingly useful hand controller and star chart. The go-to performance is as good as that of any mount I’ve used (and better than most), and the menus are all easy to access. I wouldn’t hesitate to recommend the Vixen SXD mount to anyone considering a mid-priced observing and/or astrophotography platform.

Sharing Astronomy in the Comfort of a Private and Personal Setting

By Ian Dodd

the keywords “Flagstaff bed & breakfast asStargazer’s checklist: telescope, eyepieces, tronomy.” The first hit that popped up was star charts, red flashlight, thermos of cofhttp://shootingstarinn.com/ and a quick pefee/cocoa, warm jacket, knit cap…bed & rusal of Tom’s friendly website convinced me breakfast. Now, that last item doesn’t regularly that I had found a great place for the vacashow up on an equipment list, but you may tioning stargazer. want to consider adding it and spending a A Shooting Star Inn sits at the edge of a couple of nights at A Shooting Star Inn outside of Flagstaff, Arizona.

Flagstaff, of course, has a long and rich history in astronomy. It is the home of the well preserved Lowell Observatory, where Pluto was discovered in 1930, and was named the first International Dark City in 2001 by the International Dark-Sky Association.

The 7,000 foot elevation and 300 plus days per year of sunny weather provide a regular diet of clear night skies and combine with its history to make Flagstaff a mecca for astronomer, amaOriginal inscription on the vintage Joseph Dann teur and professional alike. brass refractor But not far outside of the small meadow about a quarter mile off a lightly city, amateur astronomers will find a unique used two-lane highway 19 miles from bed & breakfast/observatory, owned and opdowntown Flagstaff. The peaks of the San erated by innkeeper/astronomer, Tom Taylor.

Francisco Mountains shadow the Inn from While making plans for a summer family vaany glow of the city’s lights to reveal a nearly cation in the area, I did a Google search with

180 degree view of some of the darkest skies you’ll ever find. Tom spent five years designing and building the Inn before opening it to guests three years ago. But this is no Thoreau’s cabin on Walden Pond. Instead, imagine a 4,200 square foot log home with three private bedrooms and baths, a cavernous living area and a kitchen that looks straight out of the pages of Gourmet magazine. But, of course, the feature of most interest to readers here will be the observatory built just off the front porch and that houses a 14-inch Meade ACF mounted on an Astro-Physics 1200 and steel pier.

After enjoying dinner in Flagstaff’s charming historic downtown, we headed out of town just as the sun was setting, arriving at A Shooting Star just after dark. Tom had obviously seen our headlights coming up the road, because he met us outside with a welcoming handshake and hello. Leading us inside, we were introduced to another couple staying there and Tom’s neighbor from across the meadow. John, the guest, Rob, the neighbor, and Tom were playing guitars and bass, enAstronomy TECHNOLOGY TODAY

35

A SHOOTING STAR INN treating John’s wife and my family to an impromptu concert of acoustic blues and folk music, a semi-regular occurrence, but not one advertised on the website. We dropped our bags in the Cassini Room, our private space for the next couple of nights, helped ourselves to a glass of wine and sat down to enjoy the music and wait for the sky to darken completely.

About 10 o’clock we ventured out to the observatory and Tom fired up the AstroPhysics mount. Using his green laser pointer, he directed us to several constellations and features of the sky usually hidden to his urban dweller guests. We took a quick peak at Saturn before it set and then the moons and bands of Jupiter. The naked-eye expanse of sky enthralled my wife, while the view through the 14-inch ACF, as compared to the 6-inch Dobsonian back home, was leaving me with a serious case of aperture fever. Unfortunately, at just that moment, the cable connection to the mount developed a short and would require some minor surgery during daylight hours.

Undaunted and determined not to disap-

36 Astronomy TECHNOLOGY TODAY

point, Tom pulled out an 8-inch Dob and pointed it at a few more objects, including star clusters and the Ring Nebula, M57, giving me my first view of the supernova remnant.

The next morning I woke up early and was enjoying the first rays of sun when Tom came out and asked if I had noticed the elk feeding in the meadow behind the house. He pulled out his 100-mm Saturn III astro-binoculars, as well as a pair of 7x42 handheld binocs, while I woke up my wife and 12-yearold son and we watched the five handsome animals for about 15 minutes as they made their way across the back of the property before disappearing into the trees. After that, we enjoyed steaming mugs of robust coffee and a hearty breakfast that Tom cooked up at his ten burner stove.

After a day of touring Flagstaff, including a stop at the Lowell Observatory and a late afternoon pick-me-up at Macy’s Coffeehouse (a local landmark Tom had directed us to), we headed back out of town just before sunset.

While the previous evening’s guests had traveled on, we were joined by two couples from

A SHOOTING STAR INN

Shooting Star Inn’s Great Room

The Giovanni Cassini Guest Room

A guest enjoys views through the Meade 14-inch ACF on its Astro-Physics 1200 Mount

Astronomy TECHNOLOGY TODAY

37

A SHOOTING STAR INN

About Tom Taylor and A Shooting Star Inn until he decided to accept a position at Kitt Peak National Observatory where he ran the observatory’s Public Night Program until taking a staff position with the Steward Observatory of the University of Arizona. While so employed, Tom was permitted to satisfy the astrophoto bug using a number of telescopes at Kitt Peak, including the 24/36 Burrell-Schmidt Camera of Case Western Reserve University, the 2.3-meter reflector of the University of Arizona, the 4meter reflector and the McMath-Pierce Solar telescope and spectrohelioscope of the National Solar Observatory.

Tom envisioned A Shooting Star Inn as an astronomical facility and retreat space suitable for any level of astronomy interest. The facility includes a fabulous collection of antique as well as new, state-of-the-art telescopes, binoculars and support equipment, and is located under the most near-perfect skies that Arizona has to offer.

Current projects include an observatory to house Tom Taylor seated next to the 100 Year Old Joseph Dann 6-inch f/13.5 refractor. the Joseph Dann antique brass refractor that is The refactor is shown on an Astro-Physics 800 Mount. one-hundred years old this year and Tom is working with fellow astronomer and glass guru, Tom Taylor, owner and operator of A Shooting Star Inn, Mike Spooner, on a new 36-inch instrument. has worked as a professional photographer for more than 25 Tom was inspired to create A Shooting Star Inn by the exyears, but has been doing astrophotography for much longer. ample of his friend, Dr. Eduardo Vega, who established SkyHe first experimented with photographing astronomical objects watchers Inn outside of Benson, Arizona. Tom and fellow while in the seventh, eighth and ninth grades grinding the astrophotographer, David Moore, first visited Skywatchers Inn glass and building the scope with which he undertook asin 1995. As Tom describes it, “We were enamored by the joy of trophotography in earnest. Tom describes himself as a selfsharing astronomy in such a private and personal setting. It was taught astronomer, although the first few of his seven years at then that I said to myself, ‘I could do this and do it very well.’” the University of Arizona were spent in its astronomy program.

Dr. Vega would, no doubt, wholeheartedly agree.

Tom holds a Masters degree and worked as a counselor

38 Astronomy TECHNOLOGY TODAY

A SHOOTING STAR INN New York who were touring Arizona on rented motorcycles. Tom had called AstroPhysics during the day for tech support on the cable problem, and much to our delight (and his, I’m sure), his mount was working again just as it should. The other guests got their first view of Saturn with the typical “Oh, my gosh!” reaction. After that we viewed M13, the Hercules star cluster, M57 (the Ring Nebula), M51 (the Whirlpool Galaxy), M27 (the Dumbbell Nebula), and concluded the evening’s viewing with Jupiter and its Galilean moons. For the native New Yorkers, a couple of whom had never before seen the Milky Way, it was a mind-blowing evening! For my family, particularly my 16 year old daughter, who has astrophysics aspirations for college and beyond, it was the first chance to see the beauty of faint objects invisible under our own light-polluted skies in Southern California.

Innkeeper Tom Taylor is an accomplished astronomer, astro-imager, photographer, musician, chief cook and bottle-washer – and a gracious host. He opens his home, his observatory and his heart to anybody who cares to go just a little off the beaten path. All who make the trip are rewarded with incredible views of the wonders of the Universe, plus hospitality they’ll never forget. Every guest is made to feel at home, either in the kitchen or under the stars, and leaves satisfied that he or she has a lifetime friend in Flagstaff. I know my family will definitely be planning a return trip to Flagstaff and A Shooting Star Inn. The next time you get the opportunity to spend some time in Northern Arizona, you should definitely plan a stay at Tom’s A Shooting Star Inn. And don’t forget your knit cap!

ASTRONOMY PRODUCTS iOptron’s MiniTower is the perfect combination of capacity and portability!

25 lbs. of Payload Born out of the popular iOptron Cube, the MiniTower is the ultimate observing solution for people who are searching for a capable and portable GoTo mount. With a standard payload of 25 lbs, a rock solid 1.5” alloy/stainless steel tripod, metal worm and gear and two dovetail adaptors, its payload can be even further enhanced by over 50% with heavy-duty accessories.

Extremely Portable With all the standard components (excluding the tripod) packaged in an alloy metal case, the MiniTower can easily be carried in a car trunk or as airline luggage. The whole system takes only 10 minutes to assemble. This unlimited portability, combined with the internal GPS, gives amateur astronomers extreme flexibility in selecting an observing location.

Accurate GoTo and Tracking Equipped with the most advanced SmartStar GoTo technology, the MiniTower is one of the most powerful and accurate GoTo mounts. The standard 8401 hand controller offers the superb navigation experience with an 8 line LCD back-lit display, a 130,000 object database and a USB port for easy connection with ASCOM compliant PC planetarium programs. With a typical GoTo accuracy of 1 arc minute and the SmartStar precision auto-tracking, the MiniTower will consistently bring the celestial object of your choice to the center of the eye-piece and keep tracking for hours.

Additional Unique Features The MiniTower is one of the most user-friendly GoTo mounts available today and is powered with features such as automatic over-current protection, automatic clutch protection for both axes, easy 3-point level adjustment, dual scope setup with two dovetails and much more!

The Binoscope Company REPAINT THAT OLD TUBE EVEN MOUNT PARTS OR PIERS! We offer the ultimate in Powdercoating Services!

All colors available in the following finishes: Gloss, Matte, Hammertone, Speckle and Metallic – we offer the entire RAL Color Chart including AP White, Tak White, Meade Blue, Matte Black, Celestron Orange, Vixen Green, and many, many more!

Ours service is NOT like buying a spray can of paint – this is Powdercoating! Your metal surface is sandblasted and powder paint is applied electrostatically and baked at high heat for 30-40 minutes. The result is a super tough paint job – better than the factory!

Check Out Our Premium Line Of Binoscopes!

WE ALSO OFFER: Airline Scope Conversion, Binobacks, Binoviewer Alignment, Cases, OTA Shortening, Sorbathane Plates, Tall Tripods, and Tandem Assembly.

w w w. b i n o s c o p e . c o m Astronomy TECHNOLOGY TODAY

39

The Virtual Observer A New Breakthrough Technology for the Visual Observer - Part 1

By Roger Blake

This article is the first of a two part series that addresses new research into the science of visual observations. It presents new, breakthrough information about how humans “see” dim, deep-space objects with a telescope and how to optimize the quality of these observations.

In this first article, I will describe some early results from a long, still-ongoing research project. My objective is to provide definitive and quantitative answers to the most fundamental questions about telescopes and visual observing: “What can I see?” “How well can I see it?” “What equipment do I need?”

To accomplish this, I developed a computer model to use as a research tool. I call it the “Virtual Observer” (for brevity, I’ll refer to it below simply as “VO”). It is a simulator of visual observations in much the same way that Microsoft's Flight Simulator (MFS) software simulates the piloting of an aircraft. One uses the MFS to learn the fundamentals of flying and the VO to learn fundamentals of observing.

The huge advantage of VO is that it permits the study, in a controlled manner, of the effects of variations of key parameters on what the observer “sees.” This degree of control is simply not possible by the direct

experience of observing in the field.

The innovation in this new technology in VO is the human component of the model that quantifies what the observer will see in the eyepiece of the telescope under a particular set of conditions. The conditions are defined by the following key parameters: 1. The deep space object 2. Target sky location (air mass) 3. Atmospheric transparency 4. Light pollution 5. Telescope specifications 6. Eyepiece specifications 7. Optical filters 8. Observer’s pupil diameter I’ll lead off with a simple example of a VO application to demonstrate how VO works and to provide familiarity with the results that it produces. Then I’ll discuss the human model component in a little more detail.

Next I’ll present more results from a wider range of VO analysis. And finally, I’ll put out a call for help, inviting you to make telescope observations that will

be used to calibrate and verify the model.

Let me start the example by posing a simple question. How well can one see M97, the Owl Nebula (shown below), in a 6-inch telescope?

What is desired here is a definitive, quantitative answer – no vague qualitative stuff! So, we must specify all of the 8 parameters. For the purpose of the example, let’s choose a light pollution level of 19.5 magnitudes per square arc-second

Astronomy TECHNOLOGY TODAY

41

THE VIRTUAL OBSERVER (MSA) and some typical values for the rest.

A 19.5 light pollution level corresponds to suburban/rural transition regions and is a relatively dark sky. I’ll address the choice of eyepieces a little later in the article. VO provides specific answers, for a specific set of conditions. I ran several different cases, keeping everything constant except the eye-

Figure 1

piece focal length, which was varied to change the magnification. The results are shown in Figure 1.

VO answers the question of visibility with a numerical value called the Visibility Index. Negative values indicate that the observer will not be able to see M97; he will see the stars in the field of view of M97, but M97 will simply not be there.

Positive values of the Visibility Index indicate that M97 will be detected. Values close to zero mean that M97 is barely visible, while larger values imply better visibility.

Values approaching 1.0 imply a photo-like image.

So what is VO telling us in Figure 1?

The first thing to notice is that VO provides separate answers for direct vision (blue) and averted vision (red). “Direct vision” refers to looking directly at the target object, placing the image in the center

42

Astronomy TECHNOLOGY TODAY

of the retina which is largely populated with cone receptors. “Averted vision” is the technique of looking away from the target slightly (5 to 20 degrees), placing the image in the peripheral region around the center of the retina which is primarily populated by rod receptors. Rods are very sensitive to dim light, but can’t see color and provide poor resolution. Cones are less sensitive, but see color and provide high resolution.

The results in Figure 1 tell us that the best magnification for direct and averted vision is at 25x and 65x respectively and confirm the fact that averted vision is more sensitive than direct vision by the much higher maximum value of the Visibility Index plotted by the averted vision curve.

But Figure 1 also tells us more. Look at the sharp break in the direct vision (blue) curve. I refer to such dramatic breaks as “cusps.” The existence of these cusps was initially a total surprise to me. They demonstrate that there is only a single magnification that will result in optimum visibility. Visibility decreases rapidly with anything higher or lower! It turns out that the cusps are a common feature in the direct vision performance curves. I’ve been in this hobby for 30 years and this was still big news to me! This is the power of a computer simulator like VO. It can take you places you haven’t been. So how’s that for definitive and quantitative answers? Wait, there’s much more to come.

But first, let me explain a little more about how VO does its job. The VO computer model is actually made up of several separate components: 1. Atmospheric - calculates how much of the light from the target reaches the

THE VIRTUAL OBSERVER telescope.

2. Light pollution - calculates the effect on contrast.

3. Telescope and eyepiece - calculates the amount of light that enters the telescope and exits the eyepiece into the eye of the observer.

4. A human model - calculates how the observer receives and interprets the light from the telescope eyepiece as the “Visibility Index.”

The first 3 models are a matter of straight-forward physics and are not reviewed further here. The real heart of VO lays in the human model component, which is modeled on the results of the definitive research performed and reported

by H. Richard Blackwell, “Contrast Thresholds of the Human Eye” (Journal of the Optical Society of America, Volume 36, Number 11, November 1946). These results remain the basis for much of today’s low-light optical design work in many fields. Blackwell’s research was conducted under a grant from the U.S. Office of

Scientific Research as part of the war effort. Testing was conducted in a specially constructed building with carefully controlled lighting conditions. The experimental procedure was to project dim images on screens in a dark room. These were observed by about two dozen human subjects who reported electronically if they were able to detect the presence of the image. In all, over two million responses were collected over a range of image sizes and illumination intensities. The measured data from these experiments were analyzed statistically and presented in Blackwell’s paper in the form of charts and tabulations of object contrast, size, and background brightness.

The telescope component of the VO model calculates the first three components and then passes them to the human model which utilizes the Blackwell data to compute the Visibility Index.

The Blackwell Data used by the VO human model was also used by Roger N. Clark in Visual Astronomy of the Deep Sky,

Introducing the TrueRC™ astrograph series from Deep Sky Instruments RC10 (uncorrected): $4,995 (Introductory price) RC10C (corrected): $ 5,995 (Introductory price) We offer two versions in the TrueRC™ series depending on your requirements. The RC10 provides Ritchey-Chrétien performance free from coma, spherical aberration and firstorder astigmatism. The RC10C adds a corrector/field flattener to remove third-order astigmatism and flatten the field for excellent star images on even today's largest CCD cameras. Both astrographs feature optics by Star Instruments, maker of RC optics for over 30 years.

www.deepskyinstruments.com Astronomy TECHNOLOGY TODAY

43

THE VIRTUAL OBSERVER

Figure 2

published in 1990. In his book, Dr. Clark used the data to determine only the optimum telescope magnification for viewing deep space objects with averted vision. This is the same as the maximum point in the upper curve in Figure 1. The VO model described here extends the application of the Blackwell data to the issue of relative and quantitative visibility.

At present, VO can only provide the Visibility Index, not actual images. The index is very useful, because it permits quantitative comparisons of results for varying conditions, but it would be nice to be able to relate the index values to images.

I will attempt this in the next phase of the

44

Astronomy TECHNOLOGY TODAY

Figure 3

project and will say more about that at the end of this article.

Now, let's return to using VO to learn a little more about the art of visual observing. In Figure 1, we were focused on a single 6-inch telescope. Now that you have some familiarity with the form of the VO results, and how to interpret them, let’s expand the analysis to a wide range of telescope sizes and see what we can learn.

I kept all the parameters the same as in Figure 1, except for the telescope diameter (clear aperture) and ran six more sets of cases, each similar to those in Figure 1, but with diameters of 6, 8, 12, 16, 20, 24 inches. The results are presented in Figure 2

(averted vision) and Figure 3 (direct vision). At this point, ignore the black “X” in each figure - I’ll discuss those later.

It was surprising to me to see how the benefits of ever larger telescopes begin to saturate above 16 inches! This phenomenon is stronger for direct vision than for averted. All of the “averted” curves show a strong visibility “cliff” at lower magnifications and all of the “direct vision” curves show the previously discussed cusps. The explanation of the cause of these features is very interesting, but, in the interest of space, will have to wait until the next article.

We can now make some generaliza-

THE VIRTUAL OBSERVER tions about visual observations made under the specific conditions assumed in these analyses (some are familiar, some are new information).

(1) Averted vision is more sensitive than direct vision. (2) For averted vision, the best magnifications for M97 falls in the range of 65x to about 90x (be careful not to reduce the magnification much below the optimum, because you can fall off the visibility cliff). (3) For direct vision, the best magnification is at the peak of the cusp. This is also defined as the minimum useable magnification and can be calculated for any scope as the scope diameter divided by the observer’s eye pupil diameter, both in the same units. Visibility falls off sharply on either side of the cusp.

The reader should keep in mind that, strictly speaking, the above generalizations only apply to the specific conditions that were held constant in all the cases. These include the following factors: 1. The deep space object 2. Target location (air mass)

3. Atmospheric transparency 4. Light pollution 5. Telescope focal ratio 6. Optical coating 7. Optical filters 8. Observers pupil diameter In a follow-up article, I’ll analyze the effects of varying some of these factors. As a teaser for the next article, I’ll show one surprising discovery here. Consider the results for an 8-inch telescope in Figures 2 and 3. Let’s imagine that this represents an observer who sets up his telescope about 10 miles west of Tampa, Florida, at the location indicated by the center of the cross-hairs in Figure 4. Figure 4 is a magnified portion of a screen shot of one of the new high-resolution light-pollution maps contained in the Dark Sky Atlas (the RGB colors that program displays on a computer monitor do not translate well to the CMYK colors on this printed page, but the reader can view the original map by downloading a free demo version of the map from www.taurus-tech.com/

Figure 4

dsa_demo.htm).

The circle around the cross-hairs in Figure 4 has a radius of 10 miles. The cross-hair center is located along the border of the red and orange colored regions.

This border corresponds to a 19.5 MSA light pollution level, the value assumed in the analysis for Figures 1, 2, and 3. The blue arrow extends from the center to a second observing site located at the edge of the circle. It traverses 10 miles, and crosses 4 different color bands, to the new site

Astronomy TECHNOLOGY TODAY

45

THE VIRTUAL OBSERVER

SUBSCRIBERS can now renew online and take advantage of a special limited time offer of $30 for 2-years!

For more information go to our website.

AstronomyTechnologyToday.com

46

Astronomy TECHNOLOGY TODAY

located along the border between the lime green and medium green color bands. This corresponds to a darker sky location with a light pollution level of 20.5 MSA. Although this is a darker site, it by no means the darkest site in the area.

I mention this to make two points about the two observing locations, center and edge, at either end of the blue arrow.

The first point is that if the observer views the sky at the zenith (just a naked eye view, no star counting) at each location on the same clear night, there is very little chance that he or she will notice much of a difference! The observer would likely dismiss the new edge location as being an insignificant improvement. I’ve done this exact experiment! Everyone can see the difference between the sky in downtown Tampa and the sky at the location at the cross-hair center, but few can tell the difference between center and the edge.

The point is that once you get away from the severe city light pollution, it is very difficult to judge the sky darkness by

visual inspection.

The second point is that the move from center to edge has a dramatic effect on image visibility. Let me return now to the black Xs in Figures 2 and 3. As stated earlier, the pink curves represent the 8inch telescope performance at location center of the cross-hairs, with a light pollution of 19.5 MSA. The black Xs represent the new visibility at edge for the same 8-inch telescope. This is an amazing result!

By driving a mere 10 miles to a slightly darker site, the observer increases the quality of his view in the 8-inch scope to one as good or better than that provided by a 20-inch telescope located back at the original site! This is true for both averted and direct vision. As you will see in the next article, light pollution challenges telescope size as the king of telescope performance factors.

This ends my technical presentation for now, but before we continue this discussion in the next article, I'd like to ask for your help in advancing this project. I

THE VIRTUAL OBSERVER want to independently verify the VO results and convert the numeric Visibility Index to actual images. Volunteers are asked to make a few telescope observations of selected objects over the next several months. I have posted a list of selected targets, data sheets, and some comparison images, on my website, www.taurustech.com. If you are interested in volunteering, please visit the site and follow the brief directions. If you have questions, just email me at rablake@erols.com. All participants will be acknowledged.

In the next article, I’ll show some preliminary comparisons of the VO model visibility predictions to actual observations. I’ll also elaborate on the cause of the visibility cliffs and cusps shown in Figures 2 and 3 above. And finally, I’ll show the results of more cases designed to investigate the effects of eye pupil diameter, telescope aperture, and light pollution on the visibility of M97.

Other analyses may follow in the future, as they become available.

Easy Lift - Heavy on Features!

Half Hitch True Grab ’n Go Mount Shake-free focusing and tracking from a mount weighing less than five pounds!

• • • • • • • •

CNC Machined and Anodized Backlash-free Slow-motions Full Two-axis Balancing Rigid Cross-braced Design Precision Bored for Encoders Excellent Tripod Clearance Preloaded Timken bearings No clutches, counterweights, or extension column • Tripod by KB Systems • Centerline loading means better performance and stability from your tripod

www.halfhitchtelecope.com

Astronomy TECHNOLOGY TODAY

47

The APT Wedge from Applied Precision Technology A Wedge that Answers the Challenge!

By Cliff De Lacy

Finding and choosing an equatorial wedge that will keep your fork-mounted telescope rigidly aligned can be a challenge.

Heavy-duty wedges come in a variety of designs, ranging from the simplest, with preset altitude angles, to those that are fully adjustable for altitude and azimuth. The former can be very stable, but must be configured and installed exactly for a single location, while the latter often trade rigidity for the ability to be adjustable.

For me, the best choice was a wedge that is fully adjustable horizontally and vertically and that could be mounted on a tripod for portability, as well as on a permanent pier. I required a wedge that made accurate alignment of the telescope position easy, without permitting the slightest shifting once the wedge is set in position.

For years I used a stock heavy-duty wedge that was manufactured in 1981 on an observatory permanent pier and later replaced it with another standard “heavy-duty” brand, but, while competent, neither fully satisfied all of my astrophotography needs. Alignment of these stock wedges tended to drift ever so slightly after the locking bolts were tightened; the telescope simply would not stay aligned on true celestial north.

I searched for and considered a number of options, but the list of those that fit my budget was fairly short. Finally, a good friend who assists me during public star gazing events suggested the wedge made by APT Astro. He had used an APT wedge for four years and praised its ease of alignment and accurate positioning on true celestial north.

Better yet, he reported that, when the setbolts were secured, there was absolutely no shift in alignment.

Encouraged, I contacted APT Astro (www.aptastro.com) and spoke with Mark Fox, its owner. APT Astro is actually a division of Applied Precision Technology, a medical equipment design and manufacturing firm located in Indiana. Its technical staff of design engineers routinely utilizes CNC machines to build products of the accuracy demanded by the medical profession.

Mr. Fox explained that APT started manufacturing astronomy wedges when his son, who is an avid amateur astronomer, became frustrated with wasted late night hours spent trying to achieve the degree of telescope/mount alignment required for long-exposure astrophotography. Mark told me, “My son, Adam, was frustrated spending too many

January nights freezing his fingers off while trying to realign his scope.” Mark told his son that he was confident he could design and build a wedge that would stay aligned. So, his son sold his old wedge and they went to work on designing a better replacement. Utilizing Applied Precision Technology’s established procedures and techniques for problem solving, they approached the wedge as yet another standard quality improvement project and designed and built a remarkable wedge that permits not the slightest shift once the adjustments are made and secured.

They first evaluated the pros and cons of the various other wedge designs and put together a list of improvements they wanted to incorporate into the new wedge. Adam contacted several experienced astrophotographers and asked that they serve as advisors and “beta testers.” Mark said, “We got a lot of really great input from these guys. We kept an open mind and used a lot of their suggestions in making design iterations.”

Mark reports that he and Adam began receiving inquiries about the new wedge even before the first prototype was completed. The astrophotography community is a small, close-knit group and news travels quickly when something new approaches the horizon.

Astronomy TECHNOLOGY TODAY

49

THE APT WEDGE FROM APPLIED PRECISION TECHNOLOGY

Image 1

APT conducted several design reviews and “tweaked” the prototypes before deciding on a final design.

How’d they do? The company reports that, in the five years that it has been selling the production model APT Wedge, they’ve yet to encounter the first dissatisfied customer.

Mark said, “We are a long way from making a perfect product, but we try very hard to build it well and to do what ever it takes to put the fun back into astronomy. There is nothing more frustrating than spending a cold winter night fussing with equipment that

Image 2

almost works.”

I obtained one of the wedges and mounted it on a permanent pier in my observatory as shown in Image 1. The wedge comes in a standard maroon color, but I chose to have mine powder coated in black instead (the wedge is available in almost any custom color). My oldest son helped me lift my Meade 14-inch LX 200R onto the new APT wedge and we attached it using replacement bolts. The original 1.5-inch bolts appeared too short, so we used 1.75-inch bolts instead and these worked perfectly.

AstroSystems is the largest supplier of telescope building components in the world!

ATM SUPPLIES

Spiders, Secondary Holders, Focusers, Eyepiece Adaptors, Secondary Mirrors, Truss Fasteners, Azimuth Pivot Kits, Teflon Kits, And More!

ACCESSORIES Our Telekit is a full featured, easy to build, and highly portable truss telescope Telescope Covers, Laminated available from 10” – 32” and starts at Atlases, Collimating Tools, only $1,150!

AstroSystems

Reflex Sights, Flashlights,

970-284-9471

Setting Circles, And More!

Laser Pointers, Seconday

www.astrosystems.biz Dew Heaters, Filters, Digital

50

Astronomy TECHNOLOGY TODAY

Image 3

The original bolts would have extended only a couple of threads into the base of the telescope and I wasn’t about to take a chance on them.

Each APT wedge is compatible with Meade LX200/LX200 SC, LX200R and RCX400 Series 10-, 12-, and 14-inch scopes. Indeed, all Meade fork-mounted telescopes that use a standard 3-hole mounting base, as well as the Celestron Nexstar and CPC 8-, 9.25-, and 11-inch fork-mounted telescopes (except the Ultima 2000) are compatible with the wedge. The APT wedge is also drilled to fit Celestron and Meade field tripods.

As seen in Image 2, an accurate bubble level is located on the top side of the wedge base plate and greatly eases leveling of the wedge assembly. The wedge provides for a wide range of horizontal adjustment. As shown in Image 3, care has been taken in the design to insure that, during polar alignment, adjustment of the lower pin does not extend to or beyond the top two stainless steel pins at the rear of the wedge. Doing so would result in damage to the azimuth (horizontal) adjustment. All adjustments, both azimuth and altitude, are made by fine-thread shafts with easy-grip knobs (see Image 4). Adjustment is silky smooth and the knobs are easy to access and adjust, even while wearing cold-weather gloves.

Once alignment is achieved, it is secured using only the two bolts that hold the lower part of the tilt plate, as seen in Image 5. Once all adjustments are completed and set, you will note that there is absolutely no shift or movement in true north celestial alignment. The upper bolts of the tilt plate, shown in Image 6, do not require tighten-

THE APT WEDGE FROM APPLIED PRECISION TECHNOLOGY

Image 4

ing and are preset by the factory. Indeed, tightening the upper bolts will void the manufacturer warranty.

The wedge also has two nylon inserts for holding 1.25-inch eyepieces, and these can be removed to reveal holes that accept 2-inch eyepieces instead.

I am truly impressed with the ease of alignment that this design provides. The wedge is simply very well designed and built.

Just attach it to your pier or tripod, make the necessary altitude and azimuth adjustments, and set them. No fumbling, image shift, or

Image 5

Image 6

chasing Polaris around the sky is required. The APT wedge will carry your heaviest mount, scope and countless accessories. Its welded, unitized construction will not rack, flex, or bend. The night after we installed the wedge, I performed the 8-minute guide adjustments in PEC noted in the Meade instruction manual and then, using a ST2000XM, did a 30second grab command for M13. The results were superb (see Image 7).

More information about the APT Astro Revolution wedge can be found at Image 7 www.aptastro.com.

Astronomy TECHNOLOGY TODAY

51

Collimation Made Easy for a Newbie With a Little Help from Friends!

By Dave Snay

I have used refractors and Schmidt Cassegrain telescopes (SCTs) for all my observing and imaging needs ever since I discovered the wonderful world of astronomy. Frankly, collimation is not something I’ve had to give a lot of thought – that is, until recently. I have never owned a refractor that had provision for collimation other than what is done at the factory. SCTs, by virtue of their peculiar design, seldom require collimation adjustment and, when they do, the process is relatively easy. There is only one optical element to adjust, the secondary mirror assembly, and on most SCTs, thanks to their short tube assemblies, the adjustment screws on the front of the scope are easy to reach while viewing through the eyepiece for immediate feedback from a defocused star. Tweak the adjustment screws until the shadow of the SCT’s secondary is perfectly centered in the defocused star and you’re done.

So, when I evaluated the 6-inch f/5

Orion astrophotography optimized Newtonian that was featured in the August 2008 issue of this magazine, I found myself in possession of a closed tube Newtonian for the first time and had no clear idea how to perform the task of checking its collimation, much less adjusting it. It had twice the collimation screws of my SCT and a defocused star gave no clear indication of which of those screws to grab first. I understood that I needed to align the Newtonian’s two mirrors, as well as the focuser drawtube, presumably along some common axis, but I had no idea how to best approach the job. So you see, no matter how long we’re involved in astronomy, we’re each of us a newbie to some aspect of its arts.

I researched online and found numerous descriptions of why collimation was important, especially to the relatively fast focal ratio Newtonians that are used for astrophotography, as well as the science involved in understanding the im-

pact of poor optic alignment. That is great information, but it did not do much for helping me understand the actual process of collimating a Newtonian. More research revealed a great many descriptions of how to collimate a reflector, many complete with complex diagrams of what one should expect to see when looking down the barrel of the focuser, but I was not able to find anything that described the process simply and efficiently enough for this Newtonian collimation novice.

Newtonian Collimation Is Easy (With a Little Help from Friends)!

Thankfully, I met Allan Keller from Farpoint Astronomical Research while at NEAF 2008. He gave me a short and simple description of how to collimate the Newtonian and loaned the tools I would need.

Here, boiled down to its essence, is what Allan described to me: First, center Astronomy TECHNOLOGY TODAY

53

COLLAMATION MADE EASY FOR A NEWBIE alignment if necessary.

Sounds simple, right? Allan stressed that the key to all this is to perform these steps in the order described and, once I understood that, the process became simple and quick.

Allan provided me with a laser and a Cheshire collimator, two tools which, as it turned out, made the job easy and accurate. I realize these tools are likely familiar to most readers, but to someone who, like me, has never experienced collimation of a Newtonian, they may be very new.

Figure 1

the secondary under the focuser drawtube. Then, align the secondary with the primary using the laser collimator. This is done by inserting the laser into the focuser and adjusting the secondary so that the laser spot hits the center mark on the primary. (If your primary does not have a center mark, Farpoint provides a center

54 Astronomy TECHNOLOGY TODAY

mark and template for accurate attachment.) To fine-tune the alignment of all optics using the Cheshire, first replace the laser with the Cheshire and then adjust the primary mirror until the center mark on the primary is centered in the alignment ring on the back of the Cheshire.

Use a defocused star to fine tune the

First Impressions My first impression of the Farpoint tools was how well they were constructed.

The laser was much heavier than I would have expected. CNC machined from a substantial block of aluminum, it features a push to click on/off switch that is recessed so that there is little chance of accidental activation. Both the Cheshire and the laser body are finely finished and anodized for a wonderfully smooth and clean appearance. It’s a very professional look.

Farpoint produces three laser collimators of different brightness levels. Each of these three laser brightness options is housed in a color coordinated body for easy identification. The red bodied laser features a 650-nm (red) laser, which is the faintest option and perfect for collimating a scope at night under dark skies. A blue bodied laser houses a 635-nm (also red) laser that is significantly brighter than that of the previous option and best for collimation under brighter twilight conditions, as well as after dark. Finally, the blue bodied option contains a 532 nm (green) laser, the brightest of the three options by far, and is most appropriate for collimation in full daylight. It can even double as a laser pointer.

The housing of each laser option is machined to fit either a 1.25-inch or 2inch focus drawtube, as required for optimum versatility.

COLLAMATION MADE EASY FOR A NEWBIE Figure 1 shows the laser that I used.

Even though the description for this laser indicates that it is best suited for collimation at night, I used it during the day with no trouble. However, I did use it inside my “observatory” with no lights, so it was probably closer to twilight conditions.

Figure 2 shows the Cheshire that I used which is the 2-inch version. Farpoint also makes a 1.25-inch version that is anodize blue.

These tools are extremely well made and Farpoint’s manufacturing precision makes them very accurate. Among the things I learned from my initial research into collimation of Newtonians was that a laser collimator that is not itself precisely collimated is all but useless. It’s is easy to envision why this would be so. Fortunately, the Farpoint laser that I used was perfectly collimated. Allan Keller maintains that the lasers will retain precise collimation with normal use. While the fit, finish and heft of the laser I used left no reason to doubt this, I don't recommend tossing any precision collimator around needlessly.

Not only was the laser beam of the collimator precisely aligned with the axis of the collimator housing, but I later determined that the substantial shoulders formed in that housing were machined precisely square with that axis. This insured that the collimator rested firmly and squarely in the focuser of the Orion Newt and left me fully confident that the spot the laser projected onto the center of the primary mirror was accurately reporting

Figure 2

the optical path formed by the focuser and secondary mirror.

Finally, I should note that the spot produced by the laser was small, bright and round. I know this to be important only because I had read that some lesser brands produce spots that are often too large or oblong to determine accurately the exact center of the spot. There was no mistaking the center point identified by the Farpoint laser.

Although it may not have been as critical to its proper function as that of the laser, the Cheshire collimator was crafted with the same high degree of fit, finish and precision. Forgive my newbie enthusiasm, but the trick that the Cheshire performs is almost magical, despite its simplicity, or perhaps because of its simplicity. My research tells me that the Farpoint Cheshire collimator is actu-

ally what many would term a “modified Cheshire.” It looks a lot like an autocollimator, at least to my untrained eye. The top of the device has a small peephole and the bottom, which faces the secondary mirror when it is installed, has a broad r eflective ring that surrounds a hole that is approximately 3/4 inch in diameter.

OPTIC-CRAFT MACHINING Manufacturer of Clock Drives from 5.6” to 32’ diameter gears. WE offer AC, DC, Stepper motors and GO-TO controllers from $440 to $4800 and Equatorial Mountings from 1” to 6” shaft diameters with a range of accessories from $300 to $12,000. Serving the Astronomical community for the last 26 years!

33918 Macomb, Farmington, MI 48335 248-476-5893 • www.OpticCraft.com

2nd Annual MakNewt Madness Sale!

FREE SHIPPING plus FREE DEWSHIELD

Mark Rieck, Owner

www.tetontelescope.com (208)403-4339 COME SEE THE VIEW FROM THE TOP!

• If you've always wanted apo refractor performance, but couldn't afford the price, Intes Micro MakNewts are the answer for you • Custom machining or tailor the accessories you want with our Teton MakNewt options • Tailoring exactly the right scope for your needs is our specialty • Unparalleled service both before and after the sale

Astronomy TECHNOLOGY TODAY

55

COLLAMATION MADE EASY FOR A NEWBIE Install it as you would an eyepiece, then look through the peephole, and you are treated to a remarkable sight. But more on that later.

Now that I’ve practiced the routine a number of times, I’d like to return to the barebones collimation steps I listed earlier.

I’m still no collimation expert by any means, but have learned a few things that may be helpful to those who are still a bit put off by the need of many Newtonians to be regularly collimated.

Step 1: Center the secondary under the focuser drawtube As I am now aware, listing this as the first step assumes that the focuser is already square to the optical tube. This was not an issue with the Orion Newt that I was testing – its focuser was firmly and squarely installed – but I can see where it could be an issue with other scopes or when the user first installs a new focuser. Once you insure that the focuser is square, judging roughly whether the secondary is accurately centered under it is fairly easy to “eyeball” without sophisticated tools. That of the Orion Newt was also accurately centered and required no adjustment on my part.

Procedures for adjusting the secondary mirror to center it will vary with scope design.

Step 2: Align the secondary with the primary using the laser collimator This step assumes that the center point of the primary mirror is clearly indicated, and as was indicated above, if your primary is not already clearly marked, Farpoint supplies center targets with its laser collimators along with templates for installing the things. The center targets are essentially small adhesive backed “donuts” of the type typically used to reinforce binder holes in loose-leaf paper. Fortunately for me, the Orion Newt also arrived with a donut style center target already

56 Astronomy TECHNOLOGY TODAY

COLLAMATION MADE EASY FOR A NEWBIE accurately installed.

I simply fastened the laser collimator in the focuser and turned it on. It revealed that the secondary required minor adjustment to move the laser spot to the exact center of the primary mirror. This was easily accomplished using the adjustment screws on the secondary mount of the Orion Newt and the direction of adjustment was obvious.

Step 3: Fine-tune the alignment of all optics using the Cheshire As I wrote earlier, this is where the real magic started for me. I had cheated a bit and adjusted the primary mirror so that the laser beam returned to the laser from the primary mirror via the secondary appeared to be centered in the laser source. The combined beams brightened a bit when they overlapped. I then inserted the Cheshire tool in the focuser and peered into the peephole. What I saw was the reflected images of the various internal components of the scope stacked one on the other and forming well aligned concentric rings around the pupil of my delighted eye.

The view through the Cheshire’s peephole showed that the image of the secondary mirror was nice and round and well centered in the image of the primary mirror. The bright reflective ring on the bottom of the Cheshire was centered in the image of the secondary mirror and the image of the “donut” primary mirror center target was, in turn, perfectly centered in the reflective Cheshire ring.

Finally, the image of the peephole through which I was peering was centered in the image of the primary’s donut target. In an instant, the cumulative images that the Cheshire highlighted demonstrated exactly what Newtonian collimation is all about (at least enough of it for my purposes that night). All was right with the world and I understood that it was the perfectly proportioned, bright reflective ring on the bottom of the Cheshire that,

along with the precisely sized peep and bottom holes, made this magic possible.

again confirmed that the optics were back in accurate collimation with the defocused image of a bright star.

Step 4: Use a defocused star to fine tune the alignment if necessary I centered a bright star in the field of view produced by a relatively short focal length eyepiece, defocused it, and was treated to a view of the shadow of the secondary mirror that appeared perfectly centered. Mission accomplished!

What would I have done had steps 3 and 4 indicated that I needed to adjust the tilt of the primary mirror? So I wouldn’t have to guess, I loosened one of the pairs of push-pull collimation screws at the back of the scope to see what the Cheshire would reveal and the component images were no longer concentric, having adopted a bias toward the side of the OTA represented by that pair of collimation screws. I returned them to their original position, locking one against other and

Lasting Impressions I cannot say enough about how easy these tools made collimating the fast 6inch Orion Newtonian. Fortunately, the scope is short enough that I could reach the primary mirror adjustment screws while looking through the Cheshire, so I could perform the operation easily. If your tube is too long for that, you can recruit a helper to adjust the primary as you direct them, or you can make small adjustments and then judge the results and repeat the process as needed.

There is at least one option to further simplify the process of collimating long tube reflectors, but that is beyond the scope of this article. However, if the process I’ve described was simple enough for this collimation newbie, I’ve every confidence it will serve you at least as well.

Astronomy TECHNOLOGY TODAY

57

Image Quality as a Function of Back Focus Shift for Cassegrain Systems Investigating Popular Cassegrains that Focus Via Changing the Spacing Between the Primary and Secondary Mirrors

By Mike Jones

Today we amateur astronomers have an enormous variety of eyepieces, cameras, manual or digital focusers, filter wheels or slides, spectrometers, photometers and other equipment that can be used with an equally wide variety of commercial and amateur-constructed Cassegrain telescopes. The location of the focal point for these different eyepieces, cameras, etc., can vary considerably relative to the telescope’s rear instrument plate, possibly by several inches. There are two ways to achieve focus: (1) have a fixed focal point and use a long-travel focuser with extension tubes, or (2) focus by changing the spacing between the Cassegrain mirrors.

If the separation of the Cassegrain mirrors is fixed, the location of the focal plane behind the primary vertex, called the back working distance (BWD), is also fixed. In this case the Cassegrain focuser must have a sufficiently long travel to accommodate the focus range for the various devices in use. Or, the focuser can have a low profile and shorter travel, and one or more extension tubes are used to hold equipment at focus. Either of these methods will work, but can potentially introduce flexure misalignment and image shift unless the focuser parts are made to

very close mechanical tolerances, or the instrumentation weight is separately supported on adjustable brackets.

An alternate focusing method is to change the Cassegrain primary and secondary mirror spacing, with the effect shown in Table 1. Most smaller commercial Cassegrains achieve focus over a range of BWD by moving the primary mirror forward or backward relative to a fixed secondary mirror. In larger instruments, however, the primary is too heavy to move, and focusing is achieved by moving the secondary. The shift in BWD depends only on the change in mirror spacing, and not on whether the primary or secondary are shifted.

Cassegrain mirrors for a desired configuration (Dall-Kirkham, classical, Ritchey-Chretien, etc.) are designed and figured for only one mirror separation and BWD. At this nominal separation and BWD, spherical aberration is (or should be) zero. Field aberrations such as coma, astigmatism and field curvature are functions of the first-order system parameters, and higher-order aberrations that depend on the mirror conic constants. Moving either the primary or secondary to shift the focal point to a new BWD location

Mirror Spacing Decrease Increase Table 1

BWD EFL Increase Increase Decrease Decrease

changes the effective focal length (EFL) and system focal ratio, roughly as the mirror shift distance multiplied by the square of the secondary amplification. But, this shift also introduces spherical aberration into the on-axis wavefront, and changes the off-axis field curvature and image quality as well.

Prior Investigations The nature and rate of deterioration in image quality with focus location is a function of the mirror radii, spacing, and conic constants. Roger Clark published an analysis1 in 1976 of focus shift sensitivity for two-mirror classical Cassegrain systems (paraboloidal primary, hyperboloidal secondary) with a central obstruction. He analyzed a wide variety of f/15 Cassegrains, with primary focal ratios ranging from f/1.9 to f/4.5. Clark employed ray-tracing to generate spot diagrams for on-axis and off-axis star images, and calculated the on-axis and off-axis RMS spot size at each mirror spacing. He Astronomy TECHNOLOGY TODAY

59

IMAGE QUALITY AS A FUNCTION OF BACK FOCUS SHIFT

Table 2 - Prescription for Clark Cassegrain (8” f/3.325 primary, f/15 EFR, BWD=20cm)

Table 3 - Configurations for Clark Cassegrain for different mirror spacings (THIC 2)

defined the maximum shift in mirror spacing to be the distance that the spacing could change and still have all the spot diagram rays fall within the Airy disk at the evaluation wavelength. Clark empirically determined that, except for low secondary amplification values, the maximum allowable shift in mirror spacing depended only on the primary mirror focal ratio. He curve-fitted his results and gave the following formula for the maximum allowable shift in mirror spacing (ΔSmax) in centimeters at evaluation wavelength λ in centimeters as: ΔSmax = 126 λ (primary f/#)4.

He also determined that the rate of image degradation either side of the nominal spacing is asymmetric, with the

60

Astronomy TECHNOLOGY TODAY

image deteriorating more rapidly as the mirror spacing decreases and the focus point shifts away from the primary. He found that the rate of image blur diameter to spacing change is about 5 to 4 either side of nominal, the higher rate being when the mirror spacing decreases. In his example, if ΔSmax is 9 cm, the mirror spacing can increase by 5 cm, but only decrease by 4 cm.

Robert E. Cox summarized Clark’s article in his October 1976 Sky and Telescope “Gleanings For ATM’s” column2.

Cox slightly reformulated the equation above for a wavelength of 0.5µm and units for ΔSmax in millimeters rather than centimeters, giving equation (2): ΔSmax = 0.063 (primary f/#)4. As Clark mentioned

in his article, Cox points out that this simple relationship is only valid for secondary amplifications above about 3X. An important point Cox implied from Clark’s article is that departing from the ideal mirror spacing not only reduces on-axis image sharpness, but also reduces the diameter of the overall Cassegrain field of good definition.

Comparison of ZEMAX and OSLO Analysis with Clark’s Results I wanted to see how RMS spot diameters from modern optical design programs compared with Clark’s 1976 results. He analyzed an 8-inch Cassegrain with an f/3.325 primary, f/15 overall

IMAGE QUALITY AS A FUNCTION OF BACK FOCUS SHIFT effective focal ratio (EFR), and a BWD of 20 cm. I keyed his Cassegrain into both the ZEMAX-EE3 and OSLO-EDU4 optical design programs. The nominal system design is given in Table 2, with dimensions in inches. The number of digits is physically meaningless, and only given for precisely comparing ZEMAX and OSLO results.

Seven system configurations having differing mirror spacings were created in ZEMAX, as shown in Table 3. The mirror separation (THIC 2) was varied from the nominal value of 20.3448 inches over a range of -6 mm to +6 mm in increments of 2 mm, and the BWD (THIC 4) optimized at each spacing for on-axis spots only. The secondary diameter was fixed at 2.200 inches and modeled as a central obstruction. The axial position of this obstruction (THIC 1) was optimized to position it precisely at the

rim of the secondary at each mirror spacing.

Figure 1 shows comparisons of the Clark, ZEMAX and OSLO analysis.

Both the ZEMAX and OSLO programs are seen to give the same RMS angular spot sizes, while Clark’s values are higher.

The cause for this is not necessarily lower pupil sampling, as the 19x19 ray ZEMAX spot RMS diameter is virtually the same as that given by the ZEMAX 200x200 spots and OSLO 100x100 spots. The fact that the ZEMAX and OSLO spots are in good agreement leads one to believe that Clark’s analysis was affected by numerical roundoff (possibly single precision) from the Honeywell 2020 compiler (which he does mention in the paper) and possibly by lower pupil sampling than I used in either ZEMAX or OSLO. He also may have optimized the BWD for both on-axis and off-axis

images, rather than just the on-axis images only; it was not clear from his paper that this was done.

The very close agreement between ZEMAX and OSLO for Clark’s system gave me good confidence to proceed with the study in this article, and to not be overly concerned about the differences from Clark’s analysis.

Geometric RMS spot size is not a preferred performance metric in this article, anyway. RMS wavefront error (WFE) and modulation transfer function (MTF) values are the preferred metrics.

Expansion Beyond Clark’s Work in this Article Clark’s paper and Cox’s “Gleanings” summary of it deal only with classical Cassegrain mirror conics. I was curious about how different Cassegrain conic

Figure 1. Comparison of RMS spot sizes using Clark’s analysis, ZEMAX and OSLO analysis Astronomy TECHNOLOGY TODAY

61

IMAGE QUALITY AS A FUNCTION OF BACK FOCUS SHIFT designs, such as Dall-Kirkham and Ritchey-Chretien curves, responded to shifting the mirror spacing and image plane. I also wanted to compare the systems using more representative RMS optical path difference (OPD) analysis rather than geometric spot diagrams, which do not accurately predict system performance at diameters approaching the Airy disk.

I have limited this article to two-mirror systems only. Cassegrains employing refractive field correctors such as modified Dall-Kirkhams and field-corrected Ritchey-Chretiens may or may not exhibit the same focus-related behavior as the plots shown in this article and would have to be individually analyzed with their precise optical prescriptions, which are often proprietary.

All Cassegrains in this article are imaging strictly at infinity for astronomical purposes. Changes in image quality with focus position for non-infinite imaging, such as for long-distance wildlife photography, as a function of conic constants,

would be an interesting additional study and can be the subject of a follow-on article.

Data Analysis Parameters I chose to expand on Clark’s analysis by investigating changes in image quality for Dall-Kirkham, classical and RitcheyChretien Cassegrain telescopes in the amateur aperture range. The only differences in these systems are the mirror conic constants (CC). The on-axis spherical aberration at nominal mirror spacing is zero for all systems, but coma, field curvature and astigmatism are functions of the conic constants. The Ritchey-Chretien coma is zero as seen in Table 4, but the field curvature is the strongest of the three.

The Pressman-Camichel Cassegrain has a spherical primary (CCP=0) and oblate spheroid secondary (CCS>0), but its coma is so enormous, and the usable field is so small, that it is not a practical system to consider unless refractive correc-

tors are employed. It was not included for analysis in this article.

An 8-inch aperture and nominal BWD of 11 inches was used for all Cassegrains analyzed in this article. Rather than varying the mirror spacing, I chose to directly vary the BWD and optimize the mirror spacing at each value. A range in BWD of 7 to 15 inches was chosen to cover a ±4-inch shift either side of the 11inch nominal BWD. The Cassegrain effective focal ratio was swept from f/7 to f/12, and seven different primary focal ratios of f/2, f/2.25, f/2.5, f/3, f/4, f/5 and f/6 were selected to show sensitivity of BWD shift for Dall-Kirkham, classical Cassegrain and Ritchey-Chretien mirror designs.

Image Degradation Metrics Clark used relatively sparse ray-trace data and RMS analysis to determine RMS spot diameters relative to Airy disk diameters. This approximation is useful when spot diagrams are much larger than the

Sole Authorized US and International Distributor MallinCam Video CCD Observational System ✯✯✯✯✯✯✯✯✯✯✯✯✯✯✯✯✯✯✯✯

SkyShed POD Retailer

Taking Video Astronomy to the Next Level!

The MallinCam HYPER PLUS • B&W or Color • Internal Mild Peltier Cooler • High QE Class 1 CCD Sensor • Reliable Hand Assembled Quality • Upgradeable • Dual Video Outputs • 1/12,000th to 56 Seconds • Integrated On Screen Menu Containing An Extensive List of Video Output Enhancement Features • In Production Veil (28 Seconds) and Eagle (14 Seconds) - single, unprocessed frames taken by Tom Osypowski of Equatorial Platforms using SpicaEyes Telescopes

Call or Write for Our MallinCam/POD Package Discounts!

985-863-2165 • www.WaningMoonII.com 62

Astronomy TECHNOLOGY TODAY

IMAGE QUALITY AS A FUNCTION OF BACK FOCUS SHIFT Airy disk, but ignores the wave nature of light and is less useful for performance comparisons when spot sizes approach or are smaller than the Airy disk.

Rather than using RMS spot diameters, I chose to use RMS wavefront error calculations in the ZEMAX-EE3 optical design program. I wrote a set of ZEMAX macros to facilitate design, analysis and exporting to Excel of the over 1300 different parametric Cassegrain systems created for this article. Root-mean-square (RMS) wavefront values are useful for assessing impacts on high-resolution visual observing in good seeing. MTF analysis out to 30-50 cycles/mm and encircled energy are appropriate metrics for digital imaging impacts, and could be the subject of a follow-on article.

I have also plotted Marechal’s λ/14 RMS level on most of the following plots.

Marechal’s limit5 is a more stringent optical performance criteria than Rayleigh’s λ/4 wave limit, stating that an optical sys-

Cass Design

Primary Conic

Secondary Conic

Coma

Dall-Kirkham Classical Cass Ritchey-Chretien

-1<CCP<0 (ellipsoid) CCP=-1 (paraboloid) CCP<-1 (hyperboloid)

CCS=0 (spherical) CCS<-1 (hyperboloidal) CCS<CCP (hyperboloidal)

Worst Less Zero

Table 4

tem with a best-focus residual RMS wavefront error of λ/14 wave or less, corresponding to a wavefront error statistical variance of about λ2/200 regardless of the profile of the residual wavefront error, cannot be visually distinguished from the performance of a perfectly corrected optical system. The Strehl value corresponding to the Marechal λ/14 RMS wavefront error limit is 0.8.

Variation in Image Quality with BWD for an 8-inch f/10 Cassegrain Figure 2 shows the changes in RMS wavefront error for an 8-inch aperture f/10 Cassegrain with f/2, f/2.5, f/3 and f/4 primary mirrors, 11-inch nominal

BWD, and at BWD shifts 4 inches either side of nominal in one inch increments.

In each plot, “R” is the Ritchey-Chretien curve, “C” is the classical Cassegrain curve, and “D” is the Dall-Kirkham curve. Several things are evident from these plots: (1) The RMS WFE increases with decreasing primary focal ratio, which agrees qualitatively with Clark’s analysis.

(2) The increase in RMS WFE is essentially linear with BWD shift in either direction away from nominal.

(3) The RMS WFE increases asymmetrically either side of nominal BWD, with the higher rate of degradation being in the direction of increasing mirror spacing and shorter BWD. This

Figure 2 - RMS wavefront errors as a function of primary focal ratio for an f/10 Cassegrain Astronomy TECHNOLOGY TODAY

63

IMAGE QUALITY AS A FUNCTION OF BACK FOCUS SHIFT behavior does not seem in general to follow his 5:4 ratio.

(4) The Ritchey-Chretien Cassegrain exhibits the highest rate of image degradation with shifting mirror position. The classical Cassegrain degrades nearly as fast as the RC, while the Dall-Kirkham system is the least sensitive to mirror shift (and actually remains below the Marechal limit over the entire BWD range).

Figures 3a and 3b show the matrix of RMS wavefront errors versus BWD for a range of primary focal ratios (PFR) (across the page) and Cassegrain effective focal ratios (EFR) (down the page).

These plots show that the worst rate of image degradation occurs at upper left, for the lowest focal ratio primaries and lowest focal ratio systems. Image quality improves toward the lower right, and more rapidly with increasing primary focal ratio than for increasing system focal ratio. In each and every configura-

64

Astronomy TECHNOLOGY TODAY

tion, the Dall-Kirkham is the least sensitive to changes in mirror spacing and BWD. Figures 4, 5, and 6 are derived from the previous plots, and show RMS WFE as a function of shift from nominal mirror spacing for f/10 effective focal ratios and primary focal ratios from f/2 to f/6.

The endpoints for maximum negative shift and for maximum positive shift have been connected together to enhance the behavior trends in the curves. All plots are plotted at the same vertical scale for comparison. Marechal’s λ/14 wave RMS WFE limit is plotted in violet for comparision.

Figure 4 shows the focus shift behavior for the 8-inch f/10 RitcheyChretien. Maximum wavefront errors decrease with increasing primary focal ratio at either distance from nominal spacing. For any given primary focal ratio, wavefront errors are slightly higher when the mirror spacing is increased and

BWD is decreased.

Figure 5 shows the focus shift behavior for the 8-inch f/10 classical Cassegrain. The RMS WFE curves are similar to the Ritchey-Chretien curves, but are not quite as high.

Figure 6 shows the focus shift curves for the 8-inch f/10 Dall-Kirkham Cassegrain. The DK curves are similar to the RC and CC curves, but the dramatic decrease in sensitivity to spacing change with the Dall-Kirkham is immediately obvious. The maximum wavefront error does not exceed Marechal’s limit anywhere over the range of mirror spacing for any of the primary focal ratios.

The trend in increasing RMS WFE with decreasing primary focal ratio at the same spacing shift is the same for all three Cassegrain designs, differing only in magnitude for the three different Cassegrains. Figures 7, 8, and 9 show these curves, but are plotted at different scales to more clearly show the curve

IMAGE QUALITY AS A FUNCTION OF BACK FOCUS SHIFT

Figure 3a - BWD vs. PFN (across) and system focal ratio (down) for f/7, f/8, f/9 EFR

Figure 3b - BWS vs PFN (across) and system focal ratio (down) for f/10, f/11, f/12 EFR

Astronomy TECHNOLOGY TODAY

65

IMAGE QUALITY AS A FUNCTION OF BACK FOCUS SHIFT

Figure 4 - RMS WFE versus shift from nominal spacing for an 8inch f/10 Ritchey-Chretien

Figure 5 - RMS WFE versus shift from nominal spacing for an 8inch f/10 classical Cassegrain

Figure 6 - RMS WFE versus shift from nominal spacing for an 8inch f/10 Dall-Kirkham

Figure 7 - Shows 8-inch Ritchey-Chretien RMS WFE versus primary and system focal ratio

Figure 8 â&#x20AC;&#x201C; Shows 8-inch Classical Cassegrain RMS WFE versus primary and system focal ratio

Figure 9 - Dall-Kirkham RMS WFE versus primary and system focal ratio

66

Astronomy TECHNOLOGY TODAY

IMAGE QUALITY AS A FUNCTION OF BACK FOCUS SHIFT only a 4th order polynomial approximation to the RC RMS WFE, with the endpoints at f/2 and f/6 matched. 5th order polynomial fits gave better fitting statistics, and the fitting coefficients for the three curves are shown below the plot. The Dall-Kirkham fitting coefficients are seen to be much less than the coefficients for the Ritchey and Classical curves.

Figure 10 - Comparison of RC, CC and DK Cassegrains at equal maximum spacing shift

shapes. All plots were at the same maximum spacing shift from nominal.

Figure 7 shows plots of RMS WFE for Ritchey-Chretiens with primary focal ratios from f/2 to f/6, and effective focal ratios (EFR) from f/7 to f/12. The maximum RMS WFE is at a primary focal ratio of f/2 and system EFR of f/7, about 0.51 waves.

Figure 8 shows plots of RMS WFE for the 8-inch classical Cassegrain with primary focal ratios from f/2 to f/6, and effective focal ratios (EFR) from f/7 to f/12. The maximum RMS WFE at a primary focal ratio of f/2 and system EFR of f/7 is about 0.4 waves.

Figure 9 shows plots of RMS WFE for the 8-inch Dall-Kirkham Cassegrain with primary focal ratios from f/2 to f/6, and effective focal ratios (EFR) from f/7 to f/12. The maximum RMS WFE at a primary focal ratio of f/2 and system EFR of f/7 is much less than the RC or CC systems, at about 0.14 waves. Once again, the Ritchey-Chretien is most sensitive to primary focal ratio, and the Dall Kirkham is the least sensitive.

Figure 10 plots RMS WFE for the

three designs, all at EFR=f/10, and at the maximum spacing and BWD shift. The curves for the three Cassegrains are similar in profile, with the much lower DallKirkham curve being evident. The curves have also been fitted using the Excel built-in polynomial fitting routine and 5th order, and fitting coefficients are shown.

Clark’s simple fourth-power law for RMS spot diameter does not quite model the changes when RMS WFE is used to evaluate performance rather than RMS spot diameters.

The red curve in Figure 10 shows

Summary This study confirmed general trends in Clark’s previous work, but showed some differences when using the more accurate RMS WFE analysis rather than RMS spot diameters. The study resulted in several interesting observations: 1. Image degradation is a strong function of primary focal ratio, as noted in Clark’s paper.

2. The maximum mirror shift is not a simple fourth-power relationship when using RMS WFE as the performance criterion.

3. The Dall-Kirkham telescope is by far the most tolerant to image shift.

4. The classical Cassegrain is next in sensitivity.

5. The Ritchey-Chretien was consistently the least tolerant to image shift regardless of primary or system focal ratio.

6. Degradation of imagery is not symmetric either side of nominal mirror spacing, but is not quite the 4:5 ratio Clark determined in his Applied Optics paper.

BIBLIOGRAPHY 1. Clark, Roger N., “Cassegrain telescopes: limits of secondary movement in secondary focusing”, Applied Optics, Vol. 15, No. 5, May, 1976, pp. 1266-1269.

2. Cox, R.E., “On Focusing a Cassegrain”, Sky and Telescope, October, 1976, p. 299.

3. ZEMAX-EE is a registered trademark of the ZEMAX Development Company, 3001 112th Avenue NE, Suite 202, Bellevue, WA 98004-8017 USA, www.zemax.com.

4. OSLO and OSLO-EDU are registered trademarks of Sinclair Optics, Inc., 5 Lacoma Lane, Pittsford NY 145340, USA, www.sinopt.com.

5. Born, Max and E. Wolf, “Principles of Optics,” 7th Edition, Cambridge University Press, 1999, p. 528.

Astronomy TECHNOLOGY TODAY

67

ASTRO TIPS tips, tricks and novel solutions

The ELF

By Craig Stark By the time you’re at a chip the size of a DSLR’s, almost every optical system is going to show some vignetting. It may not be much, but stretching your image to pull out faint DSOs, stretches the vignetting as well.

Plus, in any setup, small particles of dust can leave “donuts” on images that are a pain to process out. Both issues lead to variations in the amount of light hitting our sensor and both can be removed during processing by applying a flat field. By making an image of a perfectly even light source, we have a map of these defects and can then remove them from our light frames by simply dividing each light frame by the flat frame. But, how do we get a perfectly even light source?

Numerous solutions exist out there and I’ve tried many, but the wide FOVs I often shoot give problems for a lot of them. There are a number of plans for inexpensive “flat boxes” on the web, but these are typically fairly large devices (as they need depth to diffuse the light from bulbs or LEDs) and my shop space is currently non-existent.

Commercial solutions exist as well, but they’re expensive.

Here’s a DIY solution that anyone can

Submit Your Astro Tip! Astronomy Technology Today regularly features tips, tricks, and other novel solutions. To submit your tip, trick, or novel solution, email the following information: • A Microsoft Word document detailing your tip, trick or novel solution.

• A hi-resolution digital image in jpeg format (if available).

Please send your information to tips@astronomytechnologytoday.com

68

Astronomy TECHNOLOGY TODAY

make. If you’re a regular reader, you may have seen some of my other projects and this one is just as easy to make. I made it in about 10 minutes using tape and a kitchen knife as my only “tools.”

The heart of the system is an electroluminescent (EL) panel (www.luminousfilms.com). This film glows fairly white

when voltage is applied. I got an A3-sized (11- x 16-inch) kit complete with power inverter (that can be run off of 12V or 120V and has a knob to adjust the brightness).

Other parts included a piece of foam-board from a crafts store to provide a stiff backing for the EL sheet and some foam pipe insulation from a hardware store to build a protective frame around the unit. Total cost is under $200.

Assembly is simple. Cut the foam-board about an inch bigger than your EL sheet. I used a semi-serrated kitchen knife that worked well. Next, center the EL sheet (pink side out) on the foam board and tape it in place. Then, cut the foam pipe insulation to size to build a frame around the foam-board and after several tries (buy an extra length of insulation – it’s cheap), you’ll likely have four pieces that neatly fit around the foam-board.

When satisfied, peel off the plastic film that covers the adhesive on the pipe insulation and use that to hold the pieces on the foamboard. For added strength, use a few pieces of duct tape on the corners.

Congratulations, you’ve now built the ELF and can make perfect flats! Just place the panel over your scope, adjust the brightness as needed, and capture your flats.

BACK ISSUE SALE For a limited time you can purchase all back issues of ATT for only $20!

This is a great chance to own a complete set! Quantities are limited.

Please go to our website below for more information.

www.AstronomyTechnologyToday.com

ASTRONOMY

TECHNOLOGY TODAY

Your Complete Guide to Astronomical Equipment 3825 Gilbert Drive â&#x20AC;¢ Shreveport, LA 71104

PRST STD U.S. Postage CHANGE SERVICE REQUESTED

PAID Dallas, TX Permit No. 1767