Nov08

ASTRONOMY

TECHNOLOGY TODAY Your Complete Guide to Astronomical Equipment

THE STELLAFANE DONATION SCOPE PROJECT • VOYAGER 4.5 DYNAMIC SKY SIMULATOR BORG 50 GUIDE SCOPE AND X-Y STAGE • A CHEST NEWTONIAN FOR TRAVELERS BAFFLE OPTIMIZATION FOR CASSEGRAIN TELESCOPES

The Stellafane Donation Scope Wrapping Up The Project Volume 2 • Issue 11 November 2008 $5.00 US

Contents Industry News

Cover Story Images -31 The completed Stellafane Donation Scope graces the cover. Designed and constructed by Rob Teeter of Teeter’s Telescopes using premium components donated by a host of companies from among the industry leaders in their respective fields, the 12.5-inch f/5 Dobsonian will be auctioned or raffled to assist the Springfield Telescope Makers’ Flanders Pavilion fund. The fourth and final installment of Teeter’s four-part series detailing the design and construction of the telescope appears in this issue. Hosted by the Springfield Telescope Makers at its historic Vermont home, the annual Stellafane Convention remains the mecca of ATM enthusiasts, inspiring hundreds each year. Just as it did the 73rd annual Stellafane in 2008, the Flanders Pavilion is destined to enhance the Stellafane experience for generations.

Editor’s Note Confessions of a Star-Hopping Snob

By Gary Parkerson

45 Borg 50 Guide Scope and X-Y Stage A Solid, Versatile Guide-Scope Platform with a New X-Y Twist

By Craig Stark 51 Baffle Optimization for Cassegrain Telescopes Light Shielding is a More Complex Problem than it First Appears

By Mike Jones

14 KNIGHTWARE Offers the SQM-LE Reader

15 CATSEYE COLLIMATION Correction to October 2008 News Item

31 The Stellafane Donation Scope Project Wrapping up the Project Part 4

By Robert J. Teeter, Jr. 41 Voyager 4.5 Dynamic Sky Simulator A Full Featured Desktop Planetarium

By Erik Wilcox

12 CELESTRON Introduces CelestronImages.com

15 INNERPLANETARY PRODUCTS New Company Offers Out of this World Items

In This Issue 8

11 SKYSHED OBSERVATORIES Adds Visor to POD Options

16 OPTICAL MECHANICS Introduces the OMI Evolution-30 f/4.5 Dobsonian 61 A Chest Newtonian for Travelers Building an Ultra-Compact, Airline Carry-On Dob

By Marcin Klapczynski

17 LAZZAROTTI OPTICS Innovations to the Gladius CF250 and CF315

68 Astro Tips, Tricks, and Novel Solutions Online Forums – Ask and You Shall Receive

By Gary Parkerson 18 CATALINA SKY SURVEY ACHIEVES FIRST “Sophisticated Amateur” Captures Astroid 2008 TC3 Event

Astronomy TECHNOLOGY TODAY

5

Contributing Writers 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.

Contents New Products 21 JMI TELESCOPES Meade LNT Stabilizer Bracket and SCT Quick-Release Finder Bracket 21 LUNT SOLAR SYSTEMS Compact 35-mm Etalon System

Marcin Klapczynski is a molecular biologist and works in a research laboratory at the University of Illinois at Chicago. He is originally from Poland, and moved to the US over six years ago. Woodworking and Amateur Telescope Making are his passions. He loves to observe deep space objects, especially bright nebulas and galaxies. He is married and is addicted to coffee and his two cats.

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.

Rob Teeter is a telescope builder and owner of Teeter's Telescopes, where he has produced over 50 custom Truss-Dobsonians since 2002. Rob graduated from Rutgers University in 2005 with a degree in Environmental Policy and from Montclair State University in 2007 with a Master's Degree in Environmental Management. Rob's current day job is as an environmental regulatory compliance consultant for a private New Jersey firm.

e d t

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

22 CELESTRON Unveils New CGEM German Equatorial Mount 23 STARIZONA Introduces the HyperStar C6

24 TELE VUE OPTICS The Ethos Line Just Doubled!

26 STELLARVUE SV115T Debuts at Mid-Atlantic Astronomy Expo

can now renew their subscription online!

For more information go to our website. www.AstronomyTechnologyToday.com 6

Astronomy TECHNOLOGY TODAY

28 LVI CAMERAS Introduces SmartGuider

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.

Adirondack Astronomy www.astrovid.com page 47

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APM Telescopes www.apm-telescopes.de page 10

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Optical Mechanics www.opticalmechanics.com page 33

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Denkmeier Optical www.deepskybinoviewer.com page 66

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Ostahowski Optics www.ostahowskioptics.com page 47 Pacific Design www.casesandcovers.com page 11 ProtoStar www.fpi-protostar.com page 15

Stark Labs www.stark-labs.com page 23 Starlight Instruments www.starlightinstruments.com page 16 Stellar Technologies International www.stellar-international.com page 53 Stellarvue www.stellarvue.com page 29 Telescope Stability Systems www.telescopestabilitysystems.com page 15

Backyard Observatories www.backyardobservatories.com page 18, 19

Hands On Optics www.handsonoptics.com page 50

Quantum Scientific Imaging www.qsimaging.com page 40

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Jack’s Astro Accessories www.waningmoonii.com page 23

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JMI Telescopes www.jmitelescopes.com page 20

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

Lumicon www.lumicon.com page 46

ScopeGuard www.scopeguard.com page 32

Celestron www.celestron.com page 30

Lunt Solar Systems www.luntsolarsytems.com page 72

ScopeStuff www.scopestuff.com page 11

Chronos www.chronosmount.com page 35

Meade Instruments www.meade.com page 4, 69

Scope Trader www.scopetrader.com page 39

Wood Wonders www.wood-wonders.com page 33

DayStar Filters www.daystarfilters.com page 63

Oceanside Photo and Telescope www.optcorp.com page 36

Sirius Observatories www.siriusobservatories.com page 57

Woodland Hills Telescopes www.whtelescopes.com page 12

Carina Software www.carinasoft.com page 28

Taurus Technologies www.taurus-tech.com page 22 Tele Vue Optics www.televue.com page 70, 71 Teton Telescope www.tetontelescope.com page 58 Van Slyke Instruments www.observatory.org page 17, 25 Vixen Optics www.vixenoptics.com page 3 William Optics www.williamoptics.com page 2

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ASTRONOMY

TECHNOLOGY TODAY

Volume 2 • Issue 11 November 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.

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Astronomy TECHNOLOGY TODAY

Editor’s

Note

Gary Parkerson, Managing Editor

CONFESSIONS OF A STAR-HOPPING SNOB My Journey to Purist Conceit I’m far newer to active astronomy than most of you. In fact, it’s still less than 10 years since I first studied the heavens through the eyepiece of a telescope of my own. Oh, I paid $5 in the 1970s for a peek at Saturn through what I now know to have been a fairly large Newt stationed near Café Du Monde in New Orleans’ Jackson Square and, for all I know, that scope belonged to one of you. If so, I’d really like to know whether it was actually aimed at Saturn or merely displayed a photo of the planet. I’ve heard both claims since and wouldn’t have known the difference then.

My next telescope assisted view was again of Saturn, this time through a Dob set up in the early 1990s at a Girl Scout camp where I was the guest of my youngest daughter. I have no doubt I actually viewed the planet on that occasion and hope that scope did belong to one of you, because I’ve only this opportunity to properly thank you for a life-changing experience. Forgive me, but I didn’t know to do so at the time.

That solid-tube Dob did not fit my notion of how a telescope should look and therefore peaked my interest far more than the view alone could have, although it wasn’t until retirement from a previous career some years later that I had a chance to act on that curiosity.

Once time permitted, I experimented with telescopes of every available design before settling on a classic Newt on a German Equatorial Mount (GEM) as my favored instrument. But, whatever scope design I tried along the way, all had one thing in common: none sported modern go-to or push-to digital controls. It was oldschool for me or nothing at all! Why?

Because early in my astro-tech research, I bought into the notion that go-to and push-to were fatal to learning the night sky and have been a proponent of old-fashioned star-hopping ever since.

When it came time to find a scope and mount for Jim Osborne, our favorite prophotographer, I reasoned that he wouldn’t have time to “learn the sky” before imaging it through one of his DSLRs and, of course, would need something set up for autoguiding and PEC, and so I found myself in temporary possession of a go-to GEM. Now I could have left well enough alone and simply shipped it to him without playing with it, but that didn’t happen; I set it up in the back yard, gave it a rough polar alignment and mounted my favorite refractor on it.

As soon as enough stars were visible, I started the alignment/calibration routine with every confidence that I’d easily master that procedure. The display of the hand control asked that I confirm or deny Arcturus as the first alignment star and, because it was hiding behind a tree, I advanced to the next star on the list, Arrakis. “Arrakis?” Hmmm. I remembered the name – even had a vague notion that it was somewhere in Draco – but couldn’t find it in my Sky Atlas. (I later determined that Sky Atlas 2000.0 lists the star as “Alrakis.” Who knew?) So I scrolled through the alignment star list until I found familiar Vega and selected it. The mount slewed dutifully to Vega’s vicinity, I centered it, clicked a key to tell the mount I’d done so, and the hand control recommended the second alignment star, Altair.

“Hey, I know that one!” The mount slewed, I centered, and then the mount

asked if I wanted to double-down and go for a calibration star. Always the sucker for a long-shot, I pressed the appropriate key and…Fomalhaut? “Oh, come on! Really?

Fomalhaut?”

Here’s what I learned: years of dedicated and often tedious star hopping had indeed taught me the location of a surprising number of targets; I can point to most of the Messier objects and even a handful from the NGC. But it took a go-to mount to demonstrate that I actually know the names and locations of precious few stars.

And how many more object locations would I now know had an efficient go-to system quickly guided me to them when my labors at print charts left too little time?

Now that I’m familiar with the go-to mount we collected for Jim, I think I’ll treat myself to one as well. It’ll certainly increase my viewing efficiency and might even teach this aging dog the names and locations of some tricky stars.

Say What?

Some of you had fun with me last month for wishing safety from recent hurricanes for our friends who live in “low coastal planes.” Spell Check isn’t much help to mildly dyslectic editors! Of course, my concern was misplaced – those who reside in “planes,” whether literal or figurative, easily escaped. Not so obvious was that the same column thanked William Rison for catching an earlier error, only to compound the mistake by misspelling his last name as “Risen.” And it doesn’t stop there! I recently attempted to answer in the ATT Yahoo forum that I’d ask Christy to take care of a subscriber’s delivery problem – only I neglected the “y” that ends her name. Christy’s competence is more than sufficient; I needn’t have resorted to prayer. And I’m also the same fellow whose mom asked that I pen a thank-you note for the gift of a shirt when I was just learning to write, but who managed to leave the “r” out of the subject noun. (There’s a pattern here.) So, as you catch the inevitable few errors in this issue of ATT, please remember that they could be much worse!

1200GTO German Equatorial Mount

Incredibly Rugged Incredibly Versatile Ultimate in Portability Operate with AC power or 12 volt battery Clutches and setting circles allow manual operation if power is not available Image past the meridian for a long series of exposures without stopping to flip sides Easy alignment for non-critical viewing Components are modular for ease of servicing The keypad is a handheld computer, an external computer not needed Free keypad firmware updates Remote control with personal computer, if desired

With the advent of the CCD camera, amateurs are exploring the skies to an ever increasing level of precision. This new level puts a higher demand on the precision of the equatorial mounting. Many of the finest imagers today have been using our GTO mounts as a solid platform for a wide variety of instruments.

For moderately large instruments, the ultimate in capacity and portability is the 1200GTO.

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

9

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INDUSTRYNEWS

SKYSHED OBSERVATORIES Adds Visor to POD Options The open concept of the SkyShed POD design allows users to enjoy ready access to large swaths of the night sky while still Image 1 enjoying most of benefits of a traditional rotatable dome, but in some settings it can also permit exposure to unwanted neighboring light sources.

SkyShed chairman Wayne Parker’s newest innovation is designed to prevent this potential problem. The new POD Visor mounts on the existing pivot bolts of the user’s POD, is lightweight, black in Image 2 color, fabricated from durable plastic, and effectively converts any POD from clamshell dome into a slotted dome, in a matter of seconds.

On those occasions when the desired target requires rotating the open POD clamshell toward offending light or wind, the Visor will effectively obscure the light or block the wind. The POD Visor is also useful as added pro- Image 3 tection from dew exposure when humidity is at its worst.

The POD Visor is designed to fit just within the POD secondary dome half and to match any POD color option. With the Visor installed, opening the secondary dome half reveals the Visor located behind it. The Visor can also be lifted with the secondary dome half and into a posi-

tion that returns the POD to a fully open configuration. When you wish to use the Visor when the dome is open, simply pull it down like a pilot’s helmet visor.

In Image 1, the view of the POD resembles a traditional slotted dome. This CAD rendering shows the door in red for easy visualization.

Image 2 offers a view of the Visor alone. The actual color is black, which will not only block light, but will also act as an internal IR shield when the dome is closed during daytime. Image 3 shows a profile of POD with dome fully open and Visor fully closed.

The main design challenge was in how to mount the Visor.

Keeping it lightweight means that the user need only replace the standard pivot bolts with the slightly longer ones that are included with the Visor – the Visor is therefore mounted at the same existing dome pivot points as the secondary dome half.

Said Parker, “The addition of the Visor will make POD the world’s only 4-in1 observatory: permanent or mobile, a clam, a slide off, and a slotted dome, all in one! Use POD in whichever configuration suits your purposes or needs of the moment, or your fancy.” He continued, “Like the PZT [another recent POD option], the Visor will be retrofitable to

any POD, be available as an option for new customers, and as an add-on for existing POD owners. Price? As low as possible.

Weight? Between 10 and 20 pounds.

Availability? ASAP!” For more information on the SkyShed POD Visor and other innovative POD products, please visit www.skyshedpod.com.

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INDUSTRYNEWS

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Astronomy TECHNOLOGY TODAY

Celestron has announced its creation of CelestronImages.com. The new resource was established to provide a convenient forum for users of its telescopes and spotters to showcase the astronomy and terrestrial photographs they capture using Celestron equipment.

Although it’s still in beta format, the site has already recorded more than 1,400 images in its 18 categories. Given the focus of this publication, we were pleased to see that users enjoy posting images of their Celestron equipment, just as much as they do images captured with that equipment.

One thing that makes CelestronImages.com unique is the integration of Google Maps technology that allows Celestron to display astro photos directly on an interactive map of the night sky.

Furthermore, visitors and members can also download and share KML files that allow them to view astro images on Sky in Google Earth.

Recent enhancements to the site include a comment notification feature that sends users an automatic email notification each time someone comments on the user’s images or replies to a user’s own comments. Users are able to configure this function to personal taste in the Profile Edit screen that accompanies their memberships. Development of the site is ongoing and users are encouraged to share feedback with the site administrator who is easily accessible from the site.

The image shown is from CelestronImages.com and was posted by Justin Dildine from Hollywood, California featuring his Celestron NexStar 5i outfitted with an Orion 12.5mm illuminated reticle and Canon 300D. Our tour of CelestronImages.com provided a pleasant reminder of just how far amateur astroimaging has quickly come in recent years. The overall quality of the images is simply amazing and we look forward to returning to the site again and again.

INDUSTRYNEWS

KNIGHTWARE Introduces the SQM-LE Reader The popularity of Unihedron’s Sky Quality Meter (SQM) is growing quickly as the utility of those instruments is proven in a variety of applications, not the least of which was highlighted by Roger Blake’s Virtual Observer (VO) project, which was covered in the previous two issues of ATT. Blake’s developing VO computer simulator provides growing evidence that the relative importance of even minor increases in sky darkness has been grossly underplayed in our assumptions regarding equipment selection for various viewing conditions.

Unihedron’s SQM (shown) provides a cost effective method of quickly and easily quantifying sky conditions, allowing users to determine objectively how dark the night sky actually is, with resolution that the unaided eye/brain sensor simply cannot match. When combined with projects such as VO, the device promises more refined mapping of the dynamics of sky darkness.

We are pleased to announce that the utility of the SQM has been significantly enhanced through efforts of Knightware, which is located in central North Carolina and specializes in creating software for astronomy. Knightware’s flagship prod-

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Astronomy TECHNOLOGY TODAY

uct, Deep-Sky Planner visual observation and astro-imaging planning and logging software, has been in publication since 1994 and is in use worldwide.

Knightware recently announced the release of its newest software product, SQM-LE Reader, a Windows based software program that allows users to read Unihedron’s new SQM-LE both remotely via Internet, and locally using an Ethernet crossover cable. Knightware worked directly with Unihedron (Grimsby, Ontario) in testing the newest version of its SQM. SQM-LE Reader allows the user to read a device on demand or continuously on a periodic schedule. Readings include magnitude per square arc second, device serial number, date/time of reading and more. SQM-LE Reader runs under Windows XP SP2 or later, and Windows Vista (32 bit).

A sample screenshot is shown.

Pricing and availability SQM-LE Reader is simply “free” and “now.” It is available at http://www.knightware.biz/sqmreader.htm.

INDUSTRYNEWS

INNERPLANETARY PRODUCTS

CATSEYE COLLIMATION

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Correction to October 2008 News Item

Print and Online Issues Now Available!

New Company Offers Out of this World Items Meteorite collecting is quickly becoming a very popular hobby and InnerPlanetary Products owner Michael Carter has caught meteorite fever in a big way.

Starting with a few simple pieces, he soon found himself with a large and diverse collection. As he became more involved in the hobby, he was able to find a few large collectors who have an incredible variety of meteorites, along with huge amounts of these specimens. He created relationships with these collectors and is now able to purchase large quantities of many different types of meteorites and offer a diverse collection for sale at affordable prices.

He carries some of the rarest types of meteorites available, but also some not so rare specimens that are affordable for anyone to purchase as a gift for a son, daughter, niece, or nephew or just to keep for your own.

Choose from iron, stony, carbonaceous, lunar, Martian and more. Each meteorite comes with a certificate of authenticity.

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ASTRONOMY

TECHNOLOGY TODAY

www.astronomytechnologytoday.com

The previous issue of ATT introduced readers to Catseye Collimation’s new XLS TeleCat and TeleTube collimation tools. Unfortunately, the file photo that we included with that news item was not of either of those new products. The correct image is provided. As before, more information on the new Catseye XLS Sight Tubes is available at www.catseyecollimation.com.

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Astronomy TECHNOLOGY TODAY

15

INDUSTRYNEWS

OPTICAL MECHANICS Introduces the OMI Evolution-30 f/4.5 Dobsonian The June 2008 issue of ATT featured the design and construction of a custom 48-inch Dobsonian built

by Optical Mechanics, Inc. (OMI) for Jimi Lowrey of Fort Davis, Texas.

OMI has applied the lessons learned from that very large project to design a new 30-inch production scope that it has named the Evolution-30.

Development and planning for this project as been ongoing for the last year and OMI had begun construction of the prototype as this issue went to press. They made the first formal introduction of the scope at the Okie-Tex Star Party in October, at which point the scope existed only in virtual reality as CAD drawings. OMI plans to demonstrate a working prototype at the Texas Star Party in April of 2009.

OMI recently completed a production run of 30-inch f/4.5 mirrors and has enough on hand to equip ten of the Evo-30s, two of which have already been sold. Like the 48-inch Dob that OMI built for Jimi Lowrey, the Evo-30 will be an all metal scope. All components will be fabricated from 6061-T6 aluminum on OMI CNC machines and assembled with stainless-steel fasteners. All aluminum parts will be anodized.

The Evo-30 is designed to be a well-rounded instrument right out of the box, featuring Argo Navis digital setting circles with 10K encoders and wired and wireless hand controls, a ServoCat go-to drive system, powered ground plate, Feather Touch focuser, light shroud, Telrad and wheelbarrow handles. The secondary mirror cage will accommodate an optional 8x50 finder and laser pointer. It will feature a removable upper light baffle, 4-vane spider, 4-point

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Astronomy TECHNOLOGY TODAY

orthogonal secondary collimation and 5.5-inch minor axis secondary mirror with built-in offset.

The secondary cage attachment brackets will feature two sets of connection points - one set to accommodate most eyepiece types for visual observing and one set to provide additional out-travel for photography, video cameras and binoviewers.

The secondary mirror is sized to provide good illumination for photography, while still maintaining a central obstruction of less than 20 percent.

For more information, please visit www.opticalmechanics.com.

INDUSTRYNEWS

LAZZAROTTI OPTICS New Innovations to the Gladius CF250 and CF315 Building upon the proposition that, “If it isn’t there, it can’t cause problems!”

Lazzarotti Optics introduced its Gladius open tube Cassegrains several years ago.

Lazzarotti’s answer to tube currents and optics cool-down delays was simply to eliminate the tube and its design relied on a carbon-fiber rail system to provide the rigidity needed to maintain critical alignment of the scopes’ classical Dall-Kirkham optical components. The design also resulted in a scope that is itself as visual pleasing as the highresolution images it produces.

But, Lazzarotti didn’t stop with the success of its initial design. The latest version of the CF250 and CF315 includes several refinements that are certain to make the already excellent design even better. The primary mirror is now protected by a lightweight carbon-fiber shield which prevents fingerprints and moisture. The shield can be added and removed by hand in a very simple way with no tools and is positioned such that there is little risk of boundary layers being seen during the final mirror cooling down. Given the success of the original design, the shield need be used in critical conditions only. The shield is included with all new Gladius CF315 versions and it can be purchased separately for the Gladius CF250.

The primary mirror cap now features the option of a built-in mask to reduce the full aperture down to 230 mm (nine inches)

for when seeing conditions are particularly poor and the CF315 now includes the Baader Planetarium SteelTrack 2-inch focuser as standard equipment.

Additional enhancements include a new secondary mirror housing that is constructed from a section of carbon-fiber tube to improve overall stability. Optically, the new carbon-fiber support makes no change in terms of diffraction since it reproduces both the diameter and thickness of the original aluminum ring.

New carbon-fiber braces now run alongside the main rail to better dampen

high-frequency vibrations in windiest conditions or when the scope is coupled to a mount that inordinately transfers vibrations. The braces can be quickly removed from the rail when the telescope must be broken down into its component parts for transport or storage. Length of the rails is 98 cm (38.58 in) and they weigh approximately 50 grams (1.76 oz) each.

Gladius CF250 and CF315 are now available at the lowest prices ever, despite these new innovations. For more information, please visit www.alpineastro.com and www.lazzarotti-optics.com.

Astronomy TECHNOLOGY TODAY

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ASTRONOMY

TECHNOLOGY TODAY

CATALINA SKY SURVEY ACHIEVES FIRST “Sophisticated Amateur” Captures Asteroid 2008 TC3 Event In early October, a frequent celestial event captured rare world-wide media attention.

Reading much like the prelude to a sci-fi thriller, on October 6, 2008, the following announcement was posted by Don Yeomans, NASA/JPL Near-Earth Object Program Office, “A very small, few-meter sized asteroid, designated 2008 TC3, was found Monday morning by the Catalina Sky Survey from their observatory near Tucson Arizona.

Preliminary orbital computations by the Minor Planet Center suggested an atmospheric entry of this object within a day of discovery. JPL confirmed that an atmospheric impact will very likely occur during early morning twilight over northern Sudan, northeastern Africa, at 2:46 UT Tuesday morning.

The fireball, which could be brilliant, will travel west to east (from azimuth = 281 degrees) at a relative atmospheric impact velocity of 12.8 km/s and arrive at a very low angle (19 degrees) to the local horizon. It is very unlikely that any sizable fragments will survive passage through the Earth's atmosphere. Objects of this size would be expected to enter the Earth's atmosphere every few months on average, but this is the first time such an event has been predicted ahead of time.”

The next day, Don Yeoman’s follow-up

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read: “Confirmation has been received that the asteroid impact fireball occurred at the predicted time and place. The energy recorded was estimated to be 0.9 to 1.0 kT of TNT and the time of detection was 02:45:45 on October 7 (Greenwich Standard Time)…As reported by Peter Brown (University of Western Ontario, Canada), a preliminary examination of infrasound stations nearest to the predicted impact point shows that at least one station recorded the event. These measurements are consistent with the predicted time and place of the atmospheric impact and indicate an estimated energy of 1.1 - 2.1 kT of TNT. The follow-up astrometric observations from professional and sophisticated amateur astronomers alike were rather extraordinary, with 570 observations from 26 observatories being reported between the time of discovery by the Catalina Sky Survey to just before the object entered Earth's shadow (57 minutes prior to impact). All this happened in less than 19 hours!”

Among those who recorded aspects of the event was Dave Lane, President of the Royal Astronomical Society of Canada. Lane, pictured here, captured a remarkable sequence of 45-second exposures of the rapidly moving object taken over a period of about four hours shortly before impact. He was using equip-

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Why Backyard Observatories? ment located in his Abbey Ridge Observatory (www.davelane.ca/aro/). The remote-operation and automation of Lane’s private observatory is such that he reported, “This sequence was taken from my backyard observatory in Nova Scotia, Canada, although I was not home at the time most of the frames were taken. In fact, I was operating the observatory remotely from another observatory where I was conducting a star night for university students.” The animated GIF of the sequence of images is available at www.davelane.ca/aro/images/2008TC3.gif.

Lane describes his equipment as follows, “The observatory is based on a Technical Innovations 10-foot Home-Dome and houses a Celestron C11 SCT and either a TeleVue Genesis or Pronto refractor mounted on a Losmandy HGM-Titan German equatorial mount. An SBIG ST9 CCD camera with Optec IFW filter wheel and TCF focuser are used to image the heavens. The observatory, telescope, and CCD camera are remote-controlled from my home office (or from anywhere in the world over the Internet), which overlooks the observatory, and can ‘robotically’ perform observations and data reductions on its own. The primary use of the observatory is observing variable stars, both for the

AAVSO and relating to research conducted with colleagues at Saint Mary’s University. The observatory is also a registered observing site of the International Astronomical Union's Minor Planet Centre (site I22) and has discovered two supernovae: 2005B and 2005ea.”

Lane’s accomplishment is not only testament to his personal skill, but also indicative of the technological sophistication of the modern astro-equipment that is readily available to amateurs and surprisingly affordable as well. It should come as no surprise that Lane is also an astro-tech industry innovator. His Nova Astronomics (www.nova-astro.com) is the source for The Earth Centered Universe (ECU), a planetarium and telescope control program for Microsoft Windows. A free 30day trial version of ECU is available by download from the Nova Astronomics website.

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FACTORY INSTALLATIONS

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NEWPRODUCTS

JMI TELESCOPES

LUNT SOLAR SYSTEMS

Meade LNT Stabilizer Bracket and SCT Quick-Release Finder Bracket

Compact 35-mm Etalon System

Among the new products recently introduced by JMI are two that are destined to make finder use more convenient and safe.

The JMI LNT Stabilizer Bracket (product “BRKT125LNT”) is designed to provide the Meade SmartFinder/LNT module the additional support needed to best prevent inadvertent damage to the standard mount system. The unique design of JMI’s LNT Stabilizer Bracket accomplishes its mission without adding significant weight to the telescope assembly. This new JMI product is priced at just $40 US, a small investment for the piece of mind it provides.

SCT enthusiasts have long enjoyed the stability of finder mounts that attach directly to the SCT rear cell shoulder with screws, but most also find that configuration inconvenient when it comes time to break their scopes down for transport or storage.

Image 2

JMI now provides an easy-to-install answer to this problem with its new QuickRelease Finder Bracket (product “BRKTImage 1

FQR”). The bracket base installs in the SCT’s existing two finder-mount female threads and often with its stock screws. Its unique three-point quick-release auto-repositioning design allows for quick removal and installation with automatic realignment. Additional hardware is provided for mounting the finder rings to the bracket.

The JMI Quick-Release Finder Bracket is priced at $49 US and is available in configurations to fit Celestron SCTs from 5 inches to 11 inches, as well as newer 14-inch models. It is also available for Meade LX90s.

Image 1 shows a JMI LNT Stabilizer Bracket for Meade ETX-125 and Image 2 is JMI’s new SCT Quick-Release Finder Bracket.

For more information on both products, visit www.jmitelescopes.com.

The quickly expanding family of Lunt Solar Systems dedicated Hydrogen-alpha telescopes now includes the most compact to date, the LS35THα refractor-based system. Its unobstructed, front mounted, 35-mm etalon provides a bandpass of <0.75 Angstroms, ideal for viewing prominences and even surface detail.

The LS35THα is perfectly sized for addition to an existing solar viewing and imaging system or for use as a standalone grab-and-go solar scope. And because the LS35THα is so small and compact, it is ideally suited to sideby-side stacking for binocular viewing, making its introduction a good time to recall the Glatter binocular platform.

Priced at just $499 US, the basic LS35THα package includes the telescope assembly and standard mounting rings. The $599 US deluxe package adds a clamshell mounting system (needed for a binoviewing configuration), an LS SOL sun finder, and a 10mm LS eyepiece.

Both packages are delivered safely enclosed in a sturdy box with custom foam insert. Initial deliveries of the LS35THα are anticipated as early as November 2008. For more information and a list of dealers, please visit www.luntsolarsystems.com.

Astronomy TECHNOLOGY TODAY

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NEWPRODUCTS

CELESTRON Unveils New CGEM German Equatorial Mount To better fill the capacity gap that had existed between its popular CG5GT and CGE German equatorial mounts, Celestron recently announced the new CGEM mount that is designed to carry Celestronâ&#x20AC;&#x2122;s high-end Schmidt Cassegrain optical tubes (SCT) up to the 11-inch.

Indeed, the new mount will be available for purchase either separately, or packaged in combination with Celestronâ&#x20AC;&#x2122;s venerable 8inch, 9.25-inch and 11-inch SCTs, and we are advised that it is conservatively rated for a payload of 40 pounds, for both imaging and visual use.

The new CGEM was designed to be ergonomically friendly with large altitude and azimuth adjustment knobs for quick and easy polar alignment adjustment. It features a new and innovative polar alignment procedure called All-Star, which allows users to choose any bright star, while the software

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Astronomy TECHNOLOGY TODAY

calculates and assists with polar alignment.

Another great feature of the CGEM, sure to please astroimagers, is the Permanent Periodic Error Correction (PPEC) which will allow users to train out the worm gears periodic errors, while the mount retains the PEC recordings. Astroimagers will also enjoy that the CGEM is specifically designed to track well beyond the Meridian for uninterrupted imaging through the most ideal part of the sky.

The CGEM mount has a robust database with over 40,000 objects, 400 userdefined programmable objects, and enhanced information on over 200 objects.

It offers custom database lists of all the most famous deep-sky objects by name and catalog number; the most beautiful double, triple and quadruple stars; variable star; solar systems; objects and asterisms..

The mount uses proven NexStar computer control technology featuring flash upgradeable hand control software and motor control units for downloading product updates over the Internet. Software features include mount calibration, database filter limits, hibernate, five alignment procedures, and user-defined slew limits. The double line, 16-character Liquid Crystal Display Hand Control with 19 fiber optic back-lit LED buttons offers easy operation of go-to features.

It includes NexRemote telescope control software, for advanced control of the telescope via computer and is GPS-compatible with an optional CN16 GPS Accessory.

The Low Cog DC Servo drive motors with integrated optical encoders on both axes offer smooth, quiet operation and long life. The motor armatures are skewed to minimize cogging for enhanced low-speed tracking.

Other features include a steel worm gear and 90-mm pitch-diameter brass worm wheel, internal cable wiring for trouble-free setup and transportation, designated six-pin RJ-12 modular jack, ST-4 compatible guide port, autoguide port and auxiliary ports located on the electronic pier for long-exposure astrophotography, and RS232 communication port on hand control for control of the telescope via PC. Please watch www.celestron.com and the website of your favorite Celstron dealer for additional information.

NEWPRODUCTS

STARIZONA Introduces the HyperStar C6 Among the new products introduced at PATS 2008 was Starizona’s latest version of its popular HyperStar lens system, the HyperStar C6.

Scott Tucker of Starizona says, “It’s little, it’s cute, but it performs just like its big brothers!

The HyperStar C6 is a perfect match to one-shot color CCDs like the Starlight Xpress SXVFH9C and to video systems such as the Stellacam or Mallincam. It can cover up to an 11-mm sensor, which yields a 2.2-degree field of view at an amazingly fast f/1.9!”

HyperStar is based on Celestron's innovative Fastar feature, which allows the secondary mirror to be easily removed from Celestron’s Schmidt-Cassegrain telescopes and replaced with imaging accessories such as the HyperStar lens system. By mounting the

HyperStar lens assembly in place of the secondary mirror, a CCD camera can be mounted at the front of the telescope, allowing for a wider field of view and much faster imaging.

The HyperStar lens assembly works with a variety of cameras.

Different cameras require different adapters as spacing is critical.

One user specified adapter that is appropriate for the users camera is included with each HyperStar lens. A holder is included for safe storage of the secondary mirror while imaging.

The HyperStar C6 includes the same collimation adjustments and camera rotation system as the bigger HyperStars and is priced at $595 US. For more information on the HyperStar C6 lens, please visit www.starizona.com.

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NEWPRODUCTS

TELE VUE OPTICS The Ethos Line Just Doubled!

Just when you thought it was safe to put your checkbook away, Tele Vue introduces two new additions to its remarkable Ethos line of ultra-wide, 100-degree eyepieces. Its new 17-mm and 6-mm Ethos eyepieces debuted at PATS 2008 and initial impressions have been consistent with the accolades already directed to the existing 13-mm and 8-mm versions.

Tele Vue has issued the following statement in connection with the release of the Ethos 6 and 17 versions: “Celebrate the start of the International Year of Astronomy 2009, the 400th anniversary of Galileo’s first use of an astronomical telescope, by showing friends and neighbors the best of our wonderful universe. The Tele Vue philosophy (Ethos, if you will) has always been about inspiring ‘spacewalk’ vistas by creating the finest ‘rich field’ refractors and wide-angle eyepieces. We hope the introduction of these new Ethos models will further rekindle the appreciation of astronomy and support all the worthy goals of IYA 2009. It’s been quite a challenge to develop new Ethos eyepieces to the same performance standards achieved by the 13-mm and 8-mm models, perhaps the most honored in history. We hope the increased field of the 17 mm and the increased power of the 6 mm will open up new visual experiences that Galileo could hardly have imagined, from small refractors to the largest Dobsonians.”

Delivery to cover pre-orders of both new Ethos versions is anticipated by February 2009 and demand is already such that pre-ordering is clearly advisable.

For more information go to www.televue.com or consult your favorite Tele Vue dealer for developing details.

17-mm Ethos Specifications Apparent Field: .............100 degree Focal Length: ......................17 mm Effective Field Stop: .........29.6 mm Eye Relief:............................15 mm (accepts DIOPTRX eyesight astigmatism correctors)

Barrel Size:..............................2 inch Weight:..........................1.55 pounds (24.8 ounces)

6-mm Ethos Specifications Apparent Field: .............100 degree Focal Length: ........................6 mm Effective Field Stop: .........10.4 mm Eye relief: ............................15 mm (accepts DIOPTRX eyesight astigmatism correctors)

Barrel size: ............2 inch/1.25 inch.

Weight: .........................0.97 pounds (15.5 ounces)

Performance Summary With Tele Vue Telescopes: MAG. 21.2x 28.2x 31.8x 35.3x 38.8x 51.8x

24

17MM TRUE FOV (°) 4.71 3.53 3.14 2.83 2.57 1.93

EXIT PUPIL (MM) 2.83 2.70 3.15 2.43 3.27 1.98

Astronomy TECHNOLOGY TODAY

TELESCOPE TV-60is TV-76 TV-85 NP-127is TV-102, TV-102iis

MAG. 60.0x 80.0x 90.0x 100.0x 110.0x 146.7x

6MM TRUE FOV (°) 1.65 1.24 1.10 0.99 0.90 0.68

EXIT PUPIL (MM) 1.00 1.05 1.11 NP-101, NP101is 1.15 0.70

NEWPRODUCTS

STELLARVUE SV115T Debuts at Mid-Atlantic Astronomy Expo Vic Maris of Stellarvue debuted his new SV115T at Skies Unlimited’s MidAtlantic Astronomy Expo in October.

The 115-mm aperture, 800-mm focal length ED Apochromatic Air-Spaced Triplet is the culmination of a 2.5-year project that continues Stellarvue's tradition of excellence. The new scope is assembled and tested at Stellarvue’s Auburn California facility and is designed to provide exceptional performance with zero false color and perfect star tests.

Like all Stellarvue telescopes, each SV115T is personally Zygo and star tested by Vic Maris.

This telescope is appropriate for both visual and photographic work, with full, broadband multi-coatings for optimum performance in either application. While many refractors require field reducing adaptors for binoviewer use, the SV115T

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Astronomy TECHNOLOGY TODAY

is specifically designed for binoviewing without an adapter or corrector, thus maintaining the widest possible binoview field.

The telescope is also airline carry-on compatible when in its shortest configuration with the extension tube removed.

The SV115T is available in three configurations.

The SV115T20, which features a 2-inch, dual-speed Feather Touch focuser, is compatible with Stellarvue’s 2-inch field flattener assembly for use with small to medium sensor cameras. The SV115T20 measures 21.5 inches long with dewshield

retracted and extension tube removed for airline travel. It is 27.25 inches long in normal viewing mode and 5.5 inches longer with dewshield extended. The scope weighs approximately 11 pounds without mount rings (the included mount rings weigh approximately 1 pound each). The SV115T20 is priced at $2995 US. The SV115T30 substitutes a 3-inch, dual-speed focuser and is compatible with Stellarvue’s 3-inch field flattener assembly for use with all cameras. It includes a 2-inch adapter. The SV115T30 is also priced at $2995 US. Finally, the SV115T35 offers the SV115T30 configuration with a Feather Touch 3-inch focuser and is priced at $3395 US. All models are fully baffled for maximum contrast and feature retracting dew shields and precision CNC optical tubes. Each is delivered equipped with Stellarvue’s F2 multi-reticle finder, SVF2A 2-/1.25-inch adapter, and SVC130 hard-side case. Aluminum CNCmachined dual mounting rings are also included. For more information, please visit www.stellarvue.com.

NEWPRODUCTS

LVI CAMERAS Introduces SmartGuider LVI Cameras was formed in early 2007 to produce and market astro-imaging products designed through a collaboration of Marusca del Moretto of Microgiga Company and Paolo Lazzarotti of Lazzarotti Optics, both Italian companies. Moretto brings an extensive background in research-oriented technological partnerships, while Lazzarotti has significant experience in both astro-imaging and the design of optical systems.

LVI will initially market the SmartGuider, an innovative, stand-alone auto-guiding camera system. SmartGuiderâ&#x20AC;&#x2122;s advanced built-in logic allows correction of all tracking errors of any equatorial mount equipped with a standard ST4 auto-guider port. As a stand-alone unit, SmartGuider interfaces directly with the guide scope and mount without the requirement of a PC. The SmartGuider Control Paddle features a wide graphical display, which enables the user to constantly monitor the tracking performance and fine-tune all of the guiding corrections sent to the mount. It also has a set of easy to navigate menus for refining all camera parameters (both standard and advanced), making the SmartGuider suitable for all applications, even the most demanding.

For those who image using traditional film or DSLR cameras, the benefits are

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Astronomy TECHNOLOGY TODAY

many, with the most obvious being that they have the option of imaging with the benefits of autoguiding and without the need of a PC. This is especially significant when imaging in the field where a laptop adds demand on limited power resources. But CCD users can benefit as well. The stand-alone autoguider reduces the performance demands on the PC and thus the chances of a systems crash.

The stand-alone nature of the SmartGuider eliminates the need of using Windows device drivers for auto-guiding.

The SmartGuider camera uses a 1/3-inch monochrome Aptina MT9V032 sensor with 6micron square pixels arranged 752x480. The device features an automatic star search function, a backlit display and subpixel 2x auto-guiding to facilitate the use of guide scopes of very short focal lengths. Star focus and position are portrayed in real time on the 2.5-inch display. The hand control measures 2.2 inches by 3.8 inches by 1.1 inches and weighs 6.8 ounces, while the camera itself is 2.5 inches by 2.0 inches and weighs just 3.4 ounces.

Pictured are front and back images of the SmartGuider CCD camera with red anodized housing, along with an image of the SmartGuider hand control.

The introductory price is â&#x201A;Ź360 (US pricing available through their website) and LVI ships internationally. For more information, please visit www.lvi-cameras.com.

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OUR FINEST APO TRIPLETS Deliveries begin this year on the most advanced apo triplet refractors we have ever made, the Stellarvue Advanced Series. Working in partnership with LZOS, the largest optical manufacturer in Russia, Stellarvue has developed these telescopes over a three year period to provide the highest level of visual and photographic performance.

SV80ED Priced from $699 SV102ED Priced from $995

SV102ABV Priced from $2195 STELLARVUE HAND CRAFTED APOCHROMATIC TRIPLET REFRACTORS

Stellarvue embarked on this long term project to produce the highest quality apo triplet refractors second to none. We made a decision to pull out all the stops, improve on every area of performance and leave nothing out. We realized that this would result in telescopes that would have to sell for a slightly higher price, but we decided that if we were going to leave a legacy, this would be it.

Since these telescopes are assembled at our facility in California one at a time, we can customize them to meet your requirements at no additional cost. This includes custom tube length to meet specific needs (bino-viewing or astro-photography), custom tube diameter for lighter weight, and custom labeling. We make these for you. So once you order, Stellarvueâ&#x20AC;&#x2122;s owner, Vic Maris, will contact you personally to discuss your requirements. We promise, you will obtain the finest apo triplet refractor made to meet all of your specific needs.

CUSTOMIZED PERFECTION

SV115T Apo Triplet Priced from $2995

SV90T Fluorite Apo Triplet Priced from $1995

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The Stellafane Donation Scope Project Wrapping up the Project Part 4

By Robert J. Teeter, Jr.

What started out as a two dimensional CADD drawing of a multitude of various parts and pieces several months ago has now taken shape to become a fully functioning Truss-Dobsonian. That telescope, the Stellafane Donation Scope (SDS), has seen first light, has been outfitted with the latest electronics, and has been officially donated to the Springfield Telescope Makers. Best of all, it will soon make its way into the hands of a generous supporter.

The rear panel of the SDS mirror box displays a commemorative plaque as well as twin cooling fans and decorative “tri-stain” artwork.

Have Hand Pad, Will Slew I knew from the beginning that in order for this scope to reflect the special cause it would ultimately benefit, it would need the latest and greatest components.

A drive system was, without question, in the recipe and StellarCAT’s ServoCat system (www.stellarcat.com) was at the top of a very short list of drive options. Gary Myers was kind enough to donate one of his ServoCat Jr systems designed for use on 15-inch and smaller Dobsonians (also Astronomy TECHNOLOGY TODAY

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THE STELLAFANE DONATION SCOPE PROJECT

Close up of the SDS commemorative plaque.

adaptable for lightweight, larger apertures). Along with the drives and mounting hardware, Gary also donated StellarCAT’s Powered Ground Board (PGB) kit which will allow the use of a large 12-volt power supply that can be located away from the scope, instead of the battery having to ride “on-board” and consume valuable space in the rocker box.

When the package from StellarCAT arrived to my shop, it looked innocent enough, but when opened it gave a totally different impression. When ordering a ServoCAT system, you are provided with nearly a dozen plastic baggies containing a multitude of nuts, bolts, springs, levers and cables. A series of printed templates are

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also provided for determining where critical holes need to be drilled in the rocker box and altitude bearings of your scope.

Perhaps the most helpful inclusions with the ServoCAT are the CD and DVD which document in photo and video actual ServoCAT installs by Gary Myers and others. I found myself referring back to the pictures and videos in areas where the written documentation left any question as to how best to proceed. The DVD shows an install of a ServoCAT system on a 20-inch Obsession, so certain components and steps were different from those necessary on the 12.5-inch SDS. However, those who wish to perform an install themselves on their own non-Obsession Dobs need

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only have a rudimentary mechanical inclination. From there the DVD and CD give a complete understanding of how the system works.

Prior to donating the SDS, I had the opportunity to test the scope as a whole unit, which included giving the ServoCAT Jr a test drive. Unfortunately, the SDS had come together behind schedule and weather in the Northeast was far from cooperative, so I had far fewer hours of use of the scope than anticipated. However, during one clear night, I was able to keep objects centered, even with magnifications approaching 300x, across widely spaced portions of the sky. Once the user learns how to coordinate the directional buttons on the hand pad with motor response – a very short learning curve – slewing to objects will become a breeze. In fact, once I became accustomed to the speed of slewing I never “pushed-to” another object during the SDS observing sessions.

Staying Organized Prior to installing the ServoCAT Jr on the SDS, I had only completed one other such install, but remembered my main concern from that project: cable and wire management. I wanted to make sure the inside of the rocker box of the SDS did not turn into a “rats nest” of cabling. The problem is inherent with any Dob motordrive system since cabling is necessary between the motors, the encoders on the motors, the encoders for the digital setting circles, the hand pad, power distribution

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THE STELLAFANE DONATION SCOPE PROJECT

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The custom mirror cell by Astro Sky supports the 12.5-inch f/4.8 primary from Ostahowski Optics.

to the ServoCAT, and the digital setting circles.

Gary at StellarCAT includes wire-ties and tie-downs with the ServoCAT package, but I found that ordering an extra bag of wire clips and ties from an electronics supply store helped with the install in the particular design of the SDS. This was especially true for the relatively compact 12.5-inch scope for which some of the cabling was, of necessity, longer than needed.

Having extra wire-ties to roll and wrap that extra length was very useful.

Even more helpful was Markless Astronomics’ (www.marklessastronomics.com)

DSC Stalk II for controlling wire management, but also for locating the ServoCAT hand pad and the JMI digital setting circle computer at an optimum ergonomic position. The build quality on the DSC Stalk II is impressive to say the least. Provided cabling, connectors and materials in the construction of the products donated by Markless are all of the highest quality.

Chances are if you’ve seen a Dobsonian with a stalk mounted on the rocker box, you’ve seen Markless Astronomics’ DSC Stalk.

Connectors on the stalk allow the cabling from the ServoCAT and the associ-

Astronomy TECHNOLOGY TODAY

33

THE STELLAFANE DONATION SCOPE PROJECT In keeping with the organization theme, the Truss Pole Carry Case donated

by Shrouds by Heather (www.teeterstelescopes.com/shrouds) was constructed slightly oversized to allow the DSC Stalk II aluminum tube to be stored in the case with the eight truss poles during transport.

The Stellarvue F50W2 right-angle, illuminated-reticle finder and Rigel Quickfinder are ready for action.

ated encoders and hand pad to run up through a foam-padded and anodized aluminum tube which is topped with a heavy-duty plastic and aluminum platform that the ServoCAT hand pad and

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digital setting circle computer rest on for easy access. Rather than allowing cabling to be left dangling from the scope, the DSC Stalk II keeps everything neat and tidy.

Making the Donation Friday, August 1, 2008, had been the location of a bulls-eye on my calendar since early this year as the make or break deadline for delivery of the SDS. It had been decided that not only would this special build be donated to the Springfield Telescope Makers, but also that it would be officially donated to their club at their annual Stellafane Telescope Making Convention. Once the project became more widely known within their club, I was asked to participate in their Saturday afternoon Technical Talks, where I would highlight the build process of the scope and the reasons for its creation.

Appropriately enough, I presented my

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THE STELLAFANE DONATION SCOPE PROJECT

The Markless DSC Stalk II holds the JMI SuperMax computer and StellarCAT drive controller.

talk and displayed the SDS that afternoon in the Flanders Pavilion, which is, of course, the subject of the building fund that the eventual auction or raffle of the SDS will benefit.

I kept my talk pointed and after the rest of the Technical Talks were complete I let the SDS do the talking. At one point the SDS was completely surrounded by equipment enthusiasts testing the motions, getting a close-up view of the fit and finish and I was fielding questions from all angles. The SDS had captured the imaginations of those in attendance, many of whom were previously unaware of the build process that had been going on for the benefit of the convention.

An aspect of the scope that received much attention was the artwork performed by my friend, Max, consisting of “tri-stain” figures on the mirror box, altitude bearings, focuser board and top upper-tube-assembly ring. Max put in many hours on this project drawing, tracing, taping, cutting, staining and clearcoating to create his signature Sun-burst and Solar Flare detail work and the result

The Markless DSC Stalk II makes easy work of power cable management. Note the neat installation of the StellarCAT alt-axis drive.

did not go unappreciated. In fact, the cherry stain that has made Teeter’s Telescopes so popular, and set my scopes aside

from others, now almost looks plain in comparison to the vivid artwork Max created.

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THE STELLAFANE DONATION SCOPE PROJECT During my presentation, I was able to present and highlight to the Springfield Telescope Makers and our audience the collection of accessories that had been donated by many generous vendors and that make the SDS a complete, observationready, premium telescope system. These included Jim Fly’s CatsEye TriplePack Pro XL collimation kit, Denkmeier’s Standard Universal Power x Switch Package with 1.25-inch OCS, a matched pair of TMB/Burgess 20-mm Stellar Series eyepieces donated by Burgess Optical, TeleVue’s Tunable Top Paracorr, and a Kendrick DigiFire 7 dew-heater controller and Celestron Power Tank 17 donated by 20/20 Telescopes.

Jim Fly (www.catseyecollimation.com) donated one of his popular CatsEye TriplePack Pro XL collimation kits to ensure that SDS’s lucky owner always enjoys the stunning views that only well collimated scopes can provide. The kit includes the CatsEye Teletube XL, a sight-tube tool of adjustable length to position the secondary mirror in the exact axial position required to capture the primary light cone for maximum illumination and image contrast. It also includes the BlackCat XL Cheshire and larger primary center-mark triangle target that Jim recommends for scopes with focal lengths longer than 50 inches. The kit is rounded out by the Infinity XL autocollimator, the tool which set a new benchmark in visual clarity of alignment of the optical elements and resulting precision of final collimation.

Because Denkmeier binoviewers (www.deepskybinoviewer.com) have so greatly added to my enjoyment of my personal Teeter Dob, they were among the first components that I requested for the SDS project and the scope was designed specifically with their use in mind. Russ Lederman of Denkmeier donated Denks outfitted with its Power x Switch. SDS’s owner will not only enjoy the unique benefits of viewing through two eyes thanks to the Denks, but will be able to select

36 Astronomy TECHNOLOGY TODAY

THE STELLAFANE DONATION SCOPE PROJECT from two magnifications with nothing more than a single movement of the Power x Switch.

And to ensure that SDS’s owner has a pair of premium eyepieces on hand from day one, Bill Burgess of Burgess Optical (www.burgessoptical.com) has donated two of the new TMB/Burgess 20-mm Stellar Series eyepieces. This eyepiece series was designed to take over where the popular TMB/Burgess Planetary series left off and the Stellar Series 20s are perfect for binoviewing.

While many think of Tele Vue’s remarkable Paracorr as essential for very fast Dobs of f/4.5 and lower, the popular coma corrector was original conceived by Al Nagler with one of his >f/5 Newtonians in mind and it still benefits sub-f/8 Newts as well today. The addition of the Paracorr provides a significant increase in the diffraction limited field of the 12.5-inch f/5 SDS and the package would not have been complete without it. We thank Al Nagler and the Tele Vue family (www.televue.com) for its inclusion in the SDS system.

SDS will be very well dressed wherever it travels thanks to the donation by Shrouds by Heather (www.teetertelescopes.com/shrouds/) of a custom trussshroud. Its unique design permits the user to leave it “bunched” on the UTA when the scope is disassembled, where it need only be pulled down over the truss tubes after the scope is reassembled. It’s form-fitting and requires no fasteners or drawstrings to remain in place when fully covering the open trusses.

Finally, power for the SDS system was provided by a donation from 20/20 Telescopes and Binoculars (www.2020telescopes.com) of a Kendrick Astro Instruments DigiFire 7 controller and a Celestron Power Tank 17.

So you see, when you consider the other accessories I’ve listed in previous installments of this series, an F50W2 50mm right-angle finder and illuminated cross-hair reticle donated by Stellarvue

The ProtoStar 4-vane spider and heated secondary holder firmly support the Ostahowski Optics secondary mirror that was specifically matched to its primary.

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THE STELLAFANE DONATION SCOPE PROJECT scopes (www.astroskytelescopes.com) for its donation of a custom primary mirror cell, Moonlite Telescope Accessories (www.focuser.com) for its donation of a dual-speed, tri-knob Crayford focuser, as well as of the truss poles and its unique ball-and-socket truss connector system, JMI (www.jmitelescopes.com) for the donation of one of its SuperMax computers, and ProtoStar (www.fpi-protostar.com) for its premium 4-vane spider assembly and secondary mount with dew heater. With components like these, it’s easy to create a masterpiece.

The Moonlite Focuser carries the included Tele Vue Paracorr.

(www.stellarvue.com), and the Quickfinder Compact Reflex Sight and PulsGuide Illuminator (for the Stellarvue illuminated reticle eyepiece) donated by Rigel Systems (www.rigelsys.com), it’s easy to see that the SDS is truly a complete,

38 Astronomy TECHNOLOGY TODAY

premium observing system.

I’d like to again thank Ostahowski Optics (www.ostahowskioptics.com) for the donation of the remarkable primary mirror that is the heart of SDS, as well as for its secondary mirror, Astro Sky Tele-

The Heavens Declare the Glory of God It was very humbling for me to return to the Stellafane Convention grounds for the first time since my father, who considered this convention his favorite “star party,” passed away in 1999. I suppose it is also fitting that he had always preferred to take his time on projects, a trait he passed on to me, and that it took me ten years to

THE STELLAFANE DONATION SCOPE PROJECT come back to Stellafane with a scope that I felt was worthy of its remarkable traditions.

It is my sincere hope that SDS be viewed by all who see and use it as not only a unique piece of equipment, but also as an outlet to help the Stellafane convention maintain that rich legacy. Stellafane did much to instill a passion for astronomy in this young telescope builder in the late 1990s and I would love to see other young telescope makers continue to enjoy the same encouragement, sense of history and lasting memories of time spent with relatives and friends that only Stellafane can provide.

The Springfield Telescope Makers proudly display on their clubhouse a quote that holds special meaning for me: â&#x20AC;&#x153;The Heavens Declare the Glory of God.â&#x20AC;? Indeed they do.

For more information got to www.stellafane.org.

The Stellafane Donation Scope gets a close inspection and appreciation from many who attended Stellafane 2008.

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)

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Voyager 4.5 Dynamic Sky Simulator A Full Featured Desktop Planetarium

By Erik Wilcox

The last decade has seen a huge increase in the number of software programs aimed at the amateur astronomer, a welcome development for those of us who enjoy these products. Carina Software has been producing astronomy software for more than 20 years and its flagship Voyager program has stood the test of time. Voyager was recently enhanced with the release of version 4.5 and, while Voyager 4.5 retains all the features that loyal Voyager users have come to expect and appreciate, it includes many useful new features that will be of interest to Voyager veterans and newcomers alike.

Its improved stellar database provides more than 2.5 million stars with the CDROM version and the Voyager 4.5 DVD package brings that total to more than 155 million stars, down to Magnitude 18! Add to those 1.6 million galaxies, 40,000 variable stars, and 104,000 double stars, with a deep-sky magnitude limit of 20, and you have a truly comprehensive tool.

Like other planetarium programs that are designed to be comprehensive, Voyager offers control of go-to telescopes as well. In fact, Carina advises that Voyager 4.5 support numerous Meade products including the LX-400, LX200 Classic, LX-200 GPS, RCX-400, ETX90 and 125 (with Autostar), LXD 55 and 75, LX-90, LXD-650 and 750, and the Magellan I and II systems. It also controls Celestron’s Ultima 2000, NexStar 5 and 8, NexStar 5i and 8i, NexStar GPS, CGE German Equatorial, Advanced Series GTO, and AstroMaster platforms. Others include Losmandy Gemini and DSC, Astro-Physics GTO, SkySensor 2000,

JMI NGC-Max, Lumicon SkyVector, Orion SkyWizard, ServoCAT, Argo Navis, Super Navigator, Sky Commander, and Tangent B Box-compatible encoders, although Image 1: The orbits of the Global Positioning System (GPS) confirming compati- satellites, as seen from beyond the Moon.

4.5 that I found particularly interesting is its bility with each and every one of these platability to run on older computers that don’t forms was well beyond my capacity. It’s quite have a lot of memory or hard drive space. My a list!

PCs always seem to be lacking in those deAnd, as if to demonstrate its dedication partments, so I was anxious to test the claims. to not letting Voyager get the least bit stale, CaI picked up a copy from Scope City in San rina has already released a free, downloadable Francisco and installed Voyager 4.5 on an anupdate 4.5.1, which adds the Orion Sirius, cient desktop PC, and on my five-year-old Atlas and Intelliscopes to the list, as well as IBM ThinkPad laptop with a meager 30GB iOptron’s Smartstar and the Takahashi hard drive (remember when 30GB was a lot of Temma. For use in the field, whether when space?), both running Windows XP. Despite controlling a telescope or simply providing dethe limited memory and available space on the tailed planetarium data, Voyager 4.5 includes hard drive, Voyager 4.5 ran fine on my laptop the red-screen “night vision” friendly setting and surprisingly well even on the much less that has become a standard feature of many capable desktop, although it was sometimes a planetarium programs, but Voyager 4.5 goes bit more “jittery,” and noticeably slower on that one better: its red screen feature allows that computer. Still, having tried other fullyou to control the brightness of that display feature planetarium programs on both platwith variable dimming levels. forms, I was impressed with how smoothly Among its other enhancements, update Voyager 4.5 ran on these past-generation ma4.5.1 provides the option of avoiding loading chines. Carina recommends 1GB of memory all database files on startup, a feature that reand 700 MB of hard drive space for the Voyduces memory requirements to just 512 ager 4.5 CD-ROM version, although it can be megabytes. This specific option was requested installed with only 512MB of available memby Scope City’s Don Pensack and is just one of ory. For Macs, Mac OS X 10.3 or higher is recmany examples of Carina’s responsiveness to ommended; for PCs, Windows 2000, XP, or user feedback.

Vista is recommended.

One of the things I’d heard about Voyager Astronomy TECHNOLOGY TODAY

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VOYAGER 4.5 DYNAMIC SKY SIMULATOR

Image 2: The surface of Saturn’s moon Titan, unveiled by the Cassini spacecraft’s radar mapper.

Personally, as smoothly as it runs and as easy as it is to use, I’d love to see a scaled down version of Voyager (and Skygazer) become available as an iPhone application. The quality of screen images and animation is truly second to none; it’s clear that its designers rendered models based on the best data cur-

Image 3: The Whirlpool Galaxy (M51) plotted with background stars from the Guide Star Catalog 2 (GSC2), showing Voyager’s Telescope Control Interface.

rently available. Indeed, planets and moons use imagery from NASA’s Clementine, Magellan, Galileo and Cassini missions. Color images of Messier and many Caldwell DSO’s are embedded directly into Voyager’s sky charts, so zooming in reveals seamlessly integrated, beautiful photos of these objects. In the Home po-

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Setting Circles, And More!

sition, several different 360-degree horizon panorama options are available, including a Golden Gate Park meadow, Cathedral Rock in Arizona, a mirror-still lake in upstate New York, and a tropical beach in Hawaii (my favorite).

Many stargazers want the ability to quickly print detailed star charts, and as you would expect from software that has been refined in no small part with the help of countless suggestions and requests from actual users, Voyager 4.5 makes that easy. And for exporting charts onto web pages or other documents, PICT files (Mac) can be used with Voyager 4.5, as well as TIFF and JPEG files.

The menus are all straightforward and the program is very user-friendly. After a glance at the manual during the initial setup, I rarely had to refer to it again. Voyager 4.5 is ready to go “out of the box,” and simple to install and use. For time, there’s an interactive clock with big hands. Mousing over the hands allows you to “drag” them, changing the time, and thus the sky. It’s those little things that make a big difference, as Carina Software’s attention to detail in designing and refining Voyager 4.5 becomes more obvious with each session.

Speaking of time, Voyager 4.5 allows you to view precise planetary orbits 500,000 years into the past or future, and yes, that’s more than a million years of astronomical computations!

The information panels are all easily ac-

VOYAGER 4.5 DYNAMIC SKY SIMULATOR cessible and can be turned on or off in their entirety, and a display panel allows you to easily turn such individual functions as object names on and off as well. New orbit data for comets and asteroids are easily imported, correcting an aspect of earlier versions of Voyager that have received some criticism. Data for many recently discovered planetary moons, as well as outer solar system asteroids, Kuiper Belt objects, and “dwarf planets” are also included with Voyager 4.5, and new discoveries can be imported with the single click of a mouse. Of course, there are many, many features I haven’t mentioned, all of which would take far more space than is available in this single article.

My overall impression of Voyager 4.5 is of an excellent, reliable program that’s very simple to use. It offers incredible raw database depth and provides a wealth of useful information. And at $199.95 for the DVD version and $149.95 for the CD-ROM, the price is attractive as well. Also available from Carina is Skygazer 4, which I got to use briefly as well, and Voyager 4.5 is scheduled to have been released by the time your read this. Like Voyager, it works well, and is easy to use. The main difference is a smaller database, if one can call more than 312,000 stars and 14,500 deep-sky objects (the entire NGC/IC) small. SkyGazer is and will continue to be downloadable from the Carina website and serves an effective “demo” for Voyager since it shares the same interface and is cut from the same code, although it lacks the big database, telescope control, and some of Voyager’s more advanced user-interface features.

Either program is perfect for beginners, but advanced users will appreciate Voyager’s huge database, and it is that feature that draws me to the DVD version. We’ve included two screen shots of M8 to demonstrate the shear depth of star coverage provided in that option. Image 4 shows the Lagoon as depicted in the CD-ROM version and Image 5 reveals the additional stars that the DVD version adds.

To see how smoothly this program runs, a free demo version of Voyager 4 (version 4.5 is not yet available in demo form as I write) is available for download at www.carinasoft.com.

I personally recommend that everyone take

Image 4: The Lagoon Nebula (M8), printed with background stars from the SKYMAP, Hipparcos, and Tycho catalogs, but with no GSC2 stars shown.

Image 5: The Lagoon Nebula (M8), again, including stars from the GSC2. The comparison to Image 4 is striking!

advantage of the demo to get a feel for the basic features of Voyager before deciding whether to invest. But be forewarned, you’re

likely to find yourself upgrading to the full version of Voyager 4.5 once you’ve gotten a taste of this capable, comprehensive tool.

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Borg 50 Guide Scope and X-Y Stage A Solid, Versatile Guide-Scope Platform with a New X-Y Twist

By Craig Stark

The Mini Borg has been on the market in various incarnations for many years now and like all Borg telescopes, it comes in many flavors. As discussed in my review of the Borg 101 ED f/4 (ATT April 2008), it’s more accurate to say that it is a build-to-suit telescope that you can configure (and re-configure) to suit your needs. Astro Hutech offers a number of pre-configured versions, but these can be thought of as suggestions or examples in what is really an à la carte menu.

One suggestion, or rather set of suggestions, configures the Mini Borg as a guide scope (Image 1 on next page). I say “set of suggestions,” for while their current website lists “basic” and “deluxe” 50-mm versions, there are in fact eight variations on the theme.

In true Borg style, with the choice of two objectives, one has 16 possible configurations of the optical tube assembly (OTA) itself (and there are in fact four possible objectives). Flexibility is a central tenet of the Borg philosophy. Heck, there are even three ways you can choose to mount your guide camera to the

scope. In truth, there are even two versions of the “basic” model as well. Lest this seem daunting, I can say that with any of the configurations, you'll end up with an excellent guide scope.

The Parts The Mini Borg system has four possible objectives: a 45-mm f/7.2 ED doublet, a 50mm f/5 achromat, a 60-mm f/5.4 achromat, and a 60-mm f/5.8 ED. Since the goal here is service as a guide scope where image quality is not paramount, the least expensive objective (the 50-mm achromat) is tested here.

Next in line after the objective are a number of tubes with the number and length varying depending on how much distance is needed to let your camera (or eyepiece) reach focus. The tube length selected will vary, of course, based on what other parts you have attached (e.g., style of focuser). After this, you have a number of options to choose from.

First, you can attach a basic drawtube that slides in and out and is fixed in place with

two non-marring thumbscrews that hold it very solidly when locked down. For some, this drawtube will be used for rough focus as a helical focuser will be added downstream. If this is going to serve as a guide scope only, the drawtube can serve as the one and only focuser. It’s true that finding focus is a bit annoying with a simple drawtube, but it is effective and since this is a guide scope, odds are you can focus once and never need to change it. Being perfectly functional for this use, this serves as the focusing option in the “basic” version supplied by Astro Hutech.

Your next option is an X-Y stage that moves the camera around in the field of view.

The X-Y stage is the centerpiece of the “deluxe” version and is the place where the Borg guide scope makes a substantial departure from typical guide rigs. The stage has threads on both ends to provide a solid connection to the rest of the telescope and to your camera or fine focuser. Two screws run along sides of the stage and knurled knobs at both Astronomy TECHNOLOGY TODAY

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BORG 50 GUIDE SCOPE AND XY STAGE

Image 1: Borg guide scope with (a) drawtube , (b) X-Y stage, and (c) helical focuser all attached. For most uses, either the drawtube or the helical fine focuser would be used but not both. Several extension tubes (d) that let you customize the length of the main tube are also shown. Inset shows close-up of X-Y stage and helical focuser. Note, silver set-screws on focuser provide 3-point clamping of 1.25-inch tubes and can be removed to allow a T-mount camera to attach even more securely. The black setscrew on the bottom of the focuser locks the focuser in place.

46 Astronomy TECHNOLOGY TODAY

ends of both screws allow you to easily slide the camera around, hunting for your guide star. The system is very effective and very solid.

I’ve seen a similar looking unit from another vendor that appears to use 1.25-inch tubes and set-screws to hold things in place rather than threaded connections. Given the potential for flex in tubes, my money would be on the Borg’s threaded version. After using this, I'm ditching my rings. The motions are smooth, intuitive, and flex is a non-issue. Yes, it's that good.

Finally, you can opt for a helical fine focuser. This is another gem of a part. Like the other Borg helical focusers, the unit does not rotate, so you can remove the image of typical eyepiece fine focusers from your mind. Instead, it acts like a SLR camera lens focuser, smoothly moving in and out. It goes beyond this by providing some well thought-out details. First, it’s marked in 50-micron increments along the 10 mm of travel to let you hit the same focus position across sessions. Second, it has a nice locking mechanism to let you clamp down your focus. Third, when

BORG 50 GUIDE SCOPE AND XY STAGE using the 1.25-inch eyepiece-style connection, it uses two set screws at 120 degrees apart to provide a solid 3-point clamp onto your camera's nose (the third point being the other side of the tube). Finally, Borg thought to thread the outside edge of the focuser with T-threads so that you can hard-mount your camera onto the focuser and still have a smooth control over focus. Flex in the focuser is minimal.

Flex Tests In the last year, Iâ&#x20AC;&#x2122;ve given talks at NEAIC and at the Julian Starfest in which I covered modifications to a Meade ETX-70 refractor to get it up to snuff for guide-scope duty.

Stock, the scope had a good amount of flex in various places and since Iâ&#x20AC;&#x2122;d bought this used and in rough shape, I didn't mind solving the problems by liberally applying glue to all moving parts (once focus had been achieved). To further reduce flex, I use a T-thread adapter screwed onto the back of the built-in flip mirror assembly. The resulting guide scope still had some flex, but a lot less than it started with

and a lot less than the rigs many people use routinely. This glued-up refractor served as the basis for a comparison test with various versions of the Borg rig.

The test was simple. I mounted a main, imaging OTA (Borg 101 ED at f/6.3) and camera (Canon EOS XSi) on one side of my Telescope Stability Systems dual-saddle (Vixen-style dovetails for the scopes and a Losmandy style plate to attach to the mount).

The guide scope under test was mounted in the other saddle and a Fishcamp Starfish was attached to the guide scope (the Fishcamp is a rather substantial guide camera). For the Meade refractor, a pair of ADM adjustable rings was used and for the Borg guide scope, the supplied fixed rings were used.

The rig was placed on one side of the mount (Takahashi EM-10 riding on a Telescope Stability Systems StableMax tripod) and a distant terrestrial target (a cell phone tower about 3 miles away) was centered in both cameras by adjusting the mount (main camera) and the rings or X-Y finder (guide cam-

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BORG 50 GUIDE SCOPE AND XY STAGE

Image 2: Flex in the modified ETX-70 guide scope. Red lines indicate amount of flex (differential between images taken on both sides of the mount) in the entire system.

era). A picture was taken through each camera and the rig was rotated to the other side of the mount. By rotating the rig like this, gravity is now pulling in the opposite direction on each

48

Astronomy TECHNOLOGY TODAY

Image 3: Flex in the Borg guide scope with only the helical fine focuser attached.

part. Any differential flex between the two cameras will now be at its worst. The same target was again centered in the main camera by adjusting the mount and no adjustment was

made for the guide camera. A picture was then taken through each camera and the process was repeated for the various configurations under test.

BORG 50 GUIDE SCOPE AND XY STAGE register about 1 pixel of flex-induced drift every 7 minutes while imaging with my 8-inch f/4 scope at 2 arcseconds/pixel. With the Borg showing 10x less flex, this would come to under one pixel of flex-induced drift in my main image camera in an hour. I can certainly live with that.

Coverage Tests I mentioned before that the X-Y Image 4: Flex in the Borg guide scope with the X-Y finder and heli- finder was a joy to use. cal fine focuser attached.

Its motions were not only smooth and accuThe images were then analyzed in Photorate, but they were also far more intuitive than shop. Using the Transformation tool the image typical three-screw adjustable guide rings. I’ve scale, translation, and rotation was determined got nothing against guide rings and the pair I by overlaying the first pair of images from the own from ADM are very well-made and solid. two cameras. If there were no flex in the sysFor guide rings, I couldn't ask for anything tem at all, this same transformation could be more. However, for ease of finding a guide applied to the images from the other side of star, three-point rings leave a bit to be desired. the mount and the result would be a perfectly Or at least they do after you’ve had a chance to overlapping pair of images. If there is flex anytry the X-Y stage. What used to be a somewhere in the system, some displacement will what frustrating chore is now entirely effortless be apparent. Lines were drawn between comas one spins the knobs to smoothly and easily mon points in the two images and measured pan around the field of view. to both visually and quantitatively measure All this joy would be short lived if the adhow much flex is in each setup. It is worth rejustments were limited and this was a concern iterating that the flex shown here in Images of mine going in. How much could I move 2-4 is the total flex in the entire system. Any around in the field of view and how much of flex in either focuser, either tube, either method of mounting the tubes, etc. will show up in these images.

What we can see from these images is that the difference in flex between my current guide rig (that had its moving parts glued in place) and the Borg is nothing short of remarkable. While the Borg in various configurations ranged from 20-30 pixels (3550 arcseconds) of total flex (not all of which will be in the Borg guide scope), my other guide rig came in at 250 pixels (425 arcseconds). The other guide rig is no slouch but did

the field of view would produce decent stars?

Using the stars around Vega, I measured the total travel of the X-Y stage on the Borg guide scope at 3.6 degrees field of view (FOV) with a 1/2-inch guide chip of about 1.5 degrees and total FOV covered was 4.9 degrees over the entire adjustment range. Within this range, 2.5 degrees worth of sky produced very clean stars. Odds are pretty good you can find a guide star in a swath of sky that is five moons across and five moons high. Adjustment range is not an issue.

Conclusions The Mini Borg has long been used as a finder scope, a wide-field scope, and a travel scope. To this list, we can certainly add the ability to be a guide scope. The Borg 50-mm guide scope is well engineered for this task and has it where it counts. The guide scope is incredibly solid. All of the parts either thread together or, when tubes are used, tolerances are tight and dual set-screws are used for a rigid assembly.

The rig is also very light, weighing in at between 0.8 and 1.4 lbs (without rings or dovetail), another key consideration for a guide scope. Finally, the system is incredibly versatile. You will never be in the position of being unable to reach focus or being unable to mount something solidly to the scope. No matter which configuration you choose, you won’t go wrong. If anyone wants a glued-up old guide scope, I know where you can find one as Ted at Astro Hutech isn’t getting this Borg 50 guide scope back. Instead, he's getting my credit card number.

Astronomy TECHNOLOGY TODAY

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Baffle Optimization for Cassegrain Telescopes

By Mike Jones

Cassegrain telescopes require light shielding, or baffles, to prevent unfocused starlight from passing around the secondary mirror, through the primary mirror hole, and directly reaching focus. This unfocused light is in the form of plane waves, rather than spherical waves converging to the desired focal point. The effect is to add brightness to the image without structure, which uniformly reduces image contrast for both visual and imaging usage.

Stray light in any telescope can be easily seen using the stacked eyepiece technique I described in the October 2007 issue of Astronomy Technology Today1. The telescope is aimed into the daylight sky at a safe angle from the sun, and a medium focal length eyepiece with good eye relief is inserted into the focuser. A second eyepiece with a real focal plane, such as an orthoscopic, Kellner or Plossl design, is held over the first eyepiece, and focused to give a sharp image of the exit pupil from the

Figure 1. Stray light in an unbaffled Cassegrain (red light from star, green light random).

first eyepiece. In a Cassegrain, if you can see skylight around the secondary mirror at the exit pupil, the baffling is not designed properly.

An example of an unbaffled Cassegrain is shown in Figure 1. The randomly generated rays in red are from an infinitely distant object and are thus all parallel, and come to focus as seen. Ten thousand randomly directed rays were then spawned from a plane in front of the telescope to simulate stray light and plotted in green. It is easy to see the paths unfocused stray light (plotted in green) can take to arrive at the focal plane without having been focused by the telescope mirrors.

Optimal design of Cassegrain baffling is defined as the design that minimizes

central obscuration of the telescopeâ&#x20AC;&#x2122;s primary mirror while fully shielding the specified focal plane. This turns out to be a more complex problem than it first appears. The lengths of primary and secondary baffle tubes drive their diameters, and their diameters drive the resulting central obscuration and light blockage of the telescope entrance pupil. The secondary mirror baffle opens up toward the primary, and will in general always be larger than the secondary mirror itself. If the primary baffle is too short, the secondary baffle must be larger to block light, which increases obscuration. As the primary baffle grows longer, the secondary baffle diameter can shrink, but then the primary baffle begins to intrude into light from the inner portion of the primary mirror, again Astronomy TECHNOLOGY TODAY

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BAFFLE OPTIMIZATION FOR CASSEGRAIN TELESCOPES

Figure 2. Ray 1 is traced first, giving the secondary mirror and primary hole diameter.

Figure 3. Ray 2 is traced next, starting at the upper rim of the secondary baffle.

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acting as a central obstruction. Either extreme creates a larger central obstruction; the design goal is to find the minimum blockage that still shields the full focal plane. As will be seen, and contrary to some prior published work, this does not necessarily mean that the secondary and primary baffle obscurations have the same values at the optimum.

Several papers have appeared over the decades describing various graphical and computer methods for achieving or approximating optimal baffle design.

Andrew Young’s 1967 paper2 was the first to describe an iterative algorithm that accounts for mirror curvature, and the first to discuss the option of inclusion of baffle design in optical design codes using macro languages. Rochelle Prescott’s paper3 simplifies baffle optimization to a graphical method, but approximates the mirrors as flat surfaces. The paper

by Hales4 presents a lengthy but closedform, calculator-friendly algorithm for optimal baffle design, with the only

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BAFFLE OPTIMIZATION FOR CASSEGRAIN TELESCOPES approximations being that both mirrors are spherical rather than aspheric. This approximation has minimal impact on the mechanical dimensions of the baffles.

Halesâ&#x20AC;&#x2122; method does not require iteration, but does require solution of a fourth order quartic and selection of the proper root.

The Young and Hales papers also both begin with the assumption that the secondary and primary obscurations must be solved to be equal, which is not actually the case.

Baffle Optimization I developed the method shown in this ATT article independent of published work, at first in Visual Basic and implemented in the CassDesign program, and then in the ZEMAX5 macro language.

This method makes no approximations, and can handle higher-order aspheric mirrors as well as conics. This approximationfree, 3-ray baffle numerical optimization method presented here is different from previous published methods in that it iteratively solves for the baffle design that provides the best shielding, rather than trying to force the secondary and primary obscurations to be the same.

Optimization of Cassegrain baffling can be accomplished by tracing three rays, and iterating the baffle design to achieve simultaneous intersections of the three rays in a common plane, described separately in Figures 2, 3, and 4, and plotted together in Figure 5.

The basic telescope radii, spacing and conics are designed first, with a first guess at the secondary mirror diameter being the primary mirror diameter divided by the secondary amplification. The telescope field of view (FOV) and image dimensions are specified to accommodate the desired range of viewing and imaging devices. For square or rectangular imaging arrays, the maximum FOV is the radial distance out to the corner of the format.

To start the iteration process, a beginning value for the secondary baffle

Figure 4. Ray 3 is the cross-ray from the top of the secondary baffle to the bottom of the image.

Figure 5. All three rays used for baffle optimization, and their intersection points.

Astronomy TECHNOLOGY TODAY

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BAFFLE OPTIMIZATION FOR CASSEGRAIN TELESCOPES

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length (call this the variable “TBS”) is selected. A good starting value is about onethird of the semi-diameter of the secondary mirror determined by the approximation given above. A dummy surface at the rear of the secondary baffle is included in the raytracing.

Ray 1 (shown in blue in Figure 2) is traced first. Ray 1 is the ray from the lowest semi-field angle, traced in an ascending direction to the upper rim of the primary mirror P1-1, then to the rear plane of the secondary baffle P1-2 , and then to the secondary mirror P1-3. It then intercepts the plane at the front of the primary baffle at P1-4 , returns to and through the primary surface at P1-5 , and terminates at the uppermost point in the image plane P1-6. This ray precisely defines the diameter of the Cassegrain secondary required for 100 percent field illumination, and the minimum diameter of the hole through the Cassegrain primary mirror. The program modifies the initial Cassegrain design model with the new values for the secondary and primary hole diameters.

Ray 1 segment (P1-3 – P1-6) is used for baffle optimization.

Ray 2 (shown in red in Figure 3) is traced next. Ray 2 is sloped downward from the upper point in semi-field angle, but instead of being traced from the sky, it begins at the upper point on the rear of the secondary baffle determined by Ray 1 (P1-2 in Figure 2 and P2-1 in Figure 3, which have identical coordinates).

It descends to the primary mirror intersection P2-2 , then reflects to the front plane of the primary baffle tube P2-3, and then to secondary mirror P2-4 . Ray 2 then proceeds to the lowest point in the image at P2-5 . Ray 2 segment (P2-2 – P2-4 ) determines the taper of the primary baffle as well as being used for baffle optimization.

Ray 3 (shown in green in Figure 4) is the cross-ray from the upper point P3-1 on the upper rear of the secondary baffle tube to the lower point P3-3 in the image.

Ray 3 is not actually raytraced; its direc-

BAFFLE OPTIMIZATION FOR CASSEGRAIN TELESCOPES tion cosines are simply calculated from the coordinates of its endpoints P3-1 and P3-3.

Figure 5 shows all three rays superimposed. The circles are color-coded to show which rays are common to any given surface or ray intersection.

The three intersections of Rays 1-2, Rays 1-3 and Rays 2-3 are now calculated.

The formulas for intersection of any two rays in 2-D is given in Figure 6. Line endpoint coordinates are (xij , yij ), Ki is the direction cosine component for the ith ray along the x-axis, L is the direction cosine component for the ith ray along the yaxis, and D1 is the distance from (x11,y11) to intersection point (xi,yi).

Using this formulation, the following ray segments are intersected: Ray 1 segment (P1-3 – P1-6) and Ray 2 segment (P2-2 – P2-4) give plane P12;Ray 1 segment (P1-3 – P1-6) and Ray 3 give plane P13, and ;Ray 2 segment (P2-2 – P2-4) and Ray 3 give plane P23.

The optimal baffle design occurs when P12, P13 and P23 converge to the same location along the optical axis, making them coplanar. Their convergence location is the front of the optimized primary baffle tube.

A very fast Cassegrain was designed to test the algorithm, with the prescription shown in Table 1. The primary is an f/1.5 paraboloid, and the overall system is only f/3.6. A large field diameter of 3.0 inches was used to increase the separation between the unoptimized planes and im-

Figure 6. Formulas for intersection of any two 2-D lines

Table 1. Fast Cassegrain design used to demonstrate baffle optimizer algorithm

prove plotting visibility.

A GOTO statement was added to jump over the optimization macro code and plot the starting baffle configuration.

Figure 7 shows the locations of the P12,

P13 and P23 planes for the starting nonoptimal guess of TBS, and that they are separated and not coplanar.

A simple Newton-Raphson iterative projective technique is used to rapidly

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BAFFLE OPTIMIZATION FOR CASSEGRAIN TELESCOPES

Figure 7. Non-optimal baffling showing separation between planes P12, P13 and P23.

bring planes P12 , P13 and P23 to coplanarity. Figure 8 shows the implementation.

The horizontal axis is the value of the

56 Astronomy TECHNOLOGY TODAY

length of the secondary baffle TBS. The vertical axis is the difference between the distance d1=d12-13 between planes P12 â&#x20AC;&#x201C;P13 and the distance d2 =d13-23 be-

tween P13 -P23 along the optical axis.

The initial value for TBS gives the difference between d1 and d2. A small differential value, say 0.001", is added to TBS and the subroutine to calculate the d1-d2 difference is called again. This gives a new difference value shown as d2. The linear projection of this line to the horizontal axis at d1-d2=0 gives the estimated value of TBS required to bring the two planes to coplanarity. This value is added to the initial value of TBS, and the difference value is re-calculated.

If both mirror surfaces were approximated as planes as in Prescottâ&#x20AC;&#x2122;s paper, this technique would give the exact length of the secondary baffle tube in one linear solution cycle. But because both mirror surfaces are aspherically curved, the linear projection step is an approximation to the optimal value, and the process must be repeated a few times until convergence is reached. Four to five cycles has shown to be enough in all cases tested, even for very fast, strongly aspheric Cassegrain primar-

BAFFLE OPTIMIZATION FOR CASSEGRAIN TELESCOPES ies and systems. A numerical example of this convergence process is given in Table 2. “Delta TBS” is the value added to the length of the secondary baffle length at each iteration cycle. Notice how rapidly Delta TBS reduces, and how the length of the primary baffle tube converges, at each iteration cycle.

The technique is seen to converge rapidly, in what is termed quadratic convergence, where the residual error is roughly the square of the previous error.

In quadratic convergence, if the initial error is, say, 0.1 inches, the error value after Cycle 1 is 0.12=0.01 in., then is 0.012=0.0001 in. after Cycle 2, 0.00012=0.00000001 in. after Cycle 3, etc. The fourth or fifth iteration cycle on all cases tested gives convergence of the planes to about the diameter of a proton, which for die-hard ATM’s is just barely close enough :o).

When the baffles for the very fast system in Figure 7 have been optimized with this algorithm, the optimally baffled sys-

Figure 8. Projective Newton-Raphson iteration technique used for baffle optimization.

tem prescription is shown in Table 3, and plotted in Figure 9.

The convergence of all three planes in Figure 9 gives the secondary baffle length TBS and resulting primary baffle tube length that gives the optimal system baffling with 100% stray light shielding for the specified image format and FOV with

minimal pupil obscuration. Notice in Figure 9 that for the very strongly curved mirrors and large image formats used in this example, optimal baffling does not necessarily mean that the primary and secondary baffles result in the same obscuration; the primary baffle is seen to be slightly smaller than the secondary baffle

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BAFFLE OPTIMIZATION FOR CASSEGRAIN TELESCOPES

Table 3. Optimized baffle design prescription for fast Cassegrain example.

Making Baffle Tubes Baffling is usually built from thin, stiff sheet metal, but can also be made from thin carbon fiber laminate layups. The interior and exterior surface should ideally be dead flat black with no sheen or luster visible even down to near-graze angle.

The surfaces can be sandblasted or Table 2. Example of the numerical convergence of the baffle optimizaglass bead peened tion algorithm. to roughen the shadow. This difference in obscurations metal surface, and a very flat black paint diminishes for slower primaries and applied, such as Krylon Ultra-Flat Black, smaller image formats.

Aeroglaze Z3066, or a high-temperature

black paint for barbeque grills, exhaust manifolds, etc. The paint is lightly applied in thin multiple coats to avoid shiny, reflective pooling of the paint binder.

Baffles can be cylindrical and thus easy to make. However, at near-graze angles even the blackest, most diffuse surfaces can become specular (mirror-like), and graze-angle stray light can reflect specularly from interior and exterior surfaces, partially defeating the benefit of the baffling. Conical baffles can be used rather than cylindrical baffles, with the taper angles designed to minimize visibility as seen from both mirrors and at focus. Purists may even add additional baffle stops inside the tapered primary mirror baffle, similar to baffling a refractor, to further trap stray light.

Conclusion I have posted CassDesign2 (CD2), which implements the algorithm de-

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58 Astronomy TECHNOLOGY TODAY

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BAFFLE OPTIMIZATION FOR CASSEGRAIN TELESCOPES scribed here, in the Files section of the Yahoo group “Astronomy Technology Today.” Regarding any licensing issues, I simply certify that CassDesign2 is being made available to the public totally free of charge, with no fees or shareware donation requests, but with no liability to me. Download it, play with it, use it for a real system you build, and please report any errors you encounter on the Yahoo ATT group site. I have a real day job in optics; CD2 is strictly for fun.

Enjoy!

Bibliography: 1. Jones, M.I., “Stray Light Revealed”, Astronomy Technology Today, Oct. 2007, Issue 5, pp. 26-27.

2. Young, A.T., “Design of Cassegrain Light Shields”, Applied Optics, Vol. 6, No. 6, June, 1967, pp. 1063-1067.

3. Prescott, R., “Cassegrainian Baffle Design”, Applied Optics, Vol. 7, No. 3, March 1968, pp. 479-481.

Figure 9. Optimal baffling for the system in Figure 7.

4. Hales, W.L., “Optimum Cassegrain Baffle Systems”, Applied Optics, Vol. 31, No. 25, September, 1992, pp. 5341-5344.

5. ZEMAX® is an optical design software product of the ZEMAX Development Corporation, 3001 112th Avenue NE, Suite 202, Bellevue, WA 98004-

8017 USA, www.zemax.com.

6. Aeroglaze Z306 black absorptive polyurethane is available from the Lord Corporation, 2000 West Grandview Blvd., P.O. Box 10038, Erie, PA 165140038, 814/868-3611 ext. 3277, www.lordfulfillment.com.

Astronomy TECHNOLOGY TODAY

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Building an Ultra-Compact, Airline Carry-On Dob

By Marcin Klapczynski

I am one of those hard core ATMers who daydream every time they pass some stacked Sonotubes at a local hardware store and treat the plumbing isle as a source of parts for a homemade focuser. I have an unstoppable urge to build things out of simple parts, which when combined create a functional and, hopefully, “simply beautiful” device.

The simpler the solution is, the more satisfaction I feel. I have this weird habit of flicking through telescope catalogues and thinking, “Hmmm, this part could be actually made of three metal brackets and a couple of compression springs.” I pride myself on being able to manufacture almost anything using wood, sheet metal, a jigsaw, and a drill. Actually, the more I write about it, the more I am convinced that it is some kind of mental condition – the same condition that causes many of us to spend most of our time looking at telescope advertising pages when we “read” astronomy magazines.

My condition developed not that long ago – in 2006 I was translating and editing some astronomy news for an Internet portal and I stumbled upon an article of Ray CashLe Pennec about building a simple Dobsonian.

I was surprised to learn that such a sophisticated instrument as a Newtonian telescope could be built by any skilled DIYer. Following Ray’s guidelines, Jean Texerau’s “ATM bible,” and getting lots of advice from Internet forums, I successfully ground, polished, and figured a perfectly performing 8inch mirror, then built a telescope out of plywood and a Sonotube. And I didn’t get divorced in the process!

Visual astronomy became my passion, which was kind of problematic for someone living in Chicago, not quite a fairyland for stargazers. After a few months of star sight deprivation I was getting cranky and grumpy about it all, but at least those cloudy nights and snow up to elbows (or muggy air in the

summer) forced me to spend time improving my telescope in many ways. I added light baffling, cooling fans, balance improving springs, and finally made a split tube for portability.

A Split Tube Was Still Too Large!

Well, at least I thought that the split tube will solve the last problem. Nope. For someone who owns a Corolla, even a breakable 8-inch scope is a monstrous fit. And, arguments like, “Honey, do we really need a tent and foldable chairs for camping?” don’t work either. So under those darkest sky sites I was looking through my binoculars at M13 and thinking, “Oh boy, this thing would look awesome through my scope.” So I kept thinking I should buy a travel size telescope, maybe one from those fancy catalogues. But one day my loony mind shivered in disgust and declared, “No, you shall make one!”

Astronomy TECHNOLOGY TODAY

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A CHEST NEWTONIAN FOR TRAVELERS

Figure 1. Splitting the Sonotube is not enough for a small car owner. The “chest design” saves the day!

Figure 2. Front collimation is quick and convenient. The folded chest is quite heavy, but it can be carried by a fit individual without problem.

Figure 3. The secondary cage takes shape. Kydex was used for baffling.

Figure 4. The low profile spider can fit into a short secondary cage.

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Astronomy TECHNOLOGY TODAY

I was browsing for ideas on the Internet and stumbled upon a design by Serge Vieillard and Pierre Strock, French amateur telescope makers. I adapted the base, rocker and mirror box from their project, enlarging them a little bit. I didn’t like their secondary cage and truss mounting solutions, finding them not sturdy enough. I decided to make the chest a little bit bigger to accommodate truss tubes and additional equipment. I prefer and recommend my, more beefy version although it should be noted that the telescope I present here is still accepted as carry-on luggage by most US airlines.

Designing the Chest Scope How do you attempt to design such a telescope? Things you cannot change obviously are optics parameters – the primary mirror aperture and its focal length. First thing that should be designed and built is a secondary mirror cage, or upper tube assembly (UTA). I like an oversized UTA in order to eliminate possibility of vignetting and have shorter length tubes. That is why I have used the secondary cage of inside diameter 10 inches and a low profile focuser. I have made the rings pretty wide - 1.5 inch - which is not really necessary; I just like the look. They were connected by using threaded tube connectors tapped inside the truss tubes. Total height of the secondary mirror cage is 5 inches, which comfortably accommodates any type of focuser and a low profile spider. With some effort, the height could be further reduced, if needed.

I used a one-vane curved spider and a very simple, low-profile secondary mirror holder. The holder is made of two angle brackets, one of which is bent at 45 degrees (see Figure 4). To collimate it, one uses the three knurled knobs, which compress springs between the holder’s elements. It is tricky to position and center this kind of a spider. I had adjusted it after putting together the complete optical tube assembly (OTA), so I could actually see the alignment and pre-collimate the optics. I had planned to use two thumb screws on each side of the vane, but instead I have attached it directly to the truss tubes using metal screws. The spider is very rigid and vibration free. The secondary mirror cage defines the size of the rest of elements.

I always preassemble everything using wood screws. One should always predrill holes for even fine screws to prevent the plywood from splitting. I permanently glue all the parts only after testing the final setup in the field. Wood is graceful and forgiving material to work with, but it also contracts and expands under temperature, which is why I apply all the extra clearances.

The Mirror Box and Cell The mirror box must accommodate a mirror cell, the mirror itself, a protecting cover, and the secondary mirror cage. So the walls of the mirror box form a square with a side length equal to the outer diameter of the UTA plus 0.5 inch.

The mirror box bottom and front sides are shorter, forming a frontal notch that will help to make the rocker box lower (see Figure 5). The back wall has to have an opening for the focuser that will stick out from the secondary cage while packed up. In order to easily pull the secondary cage out of the mirror box, all its walls should be 0.5 inch lower in the middle than at corners. Height of the mirror box is summary of: height of the primary mirror cell plus 1.0 inch, the primary mirror thickness plus 0.5 inch, and height of the secondary mirror cage.

The mirror cell is a flotation system with 9 points of support and a sling.

Because the mirror box must fit into the chest for transport, one cannot use typ-

A CHEST NEWTONIAN FOR TRAVELERS

Figure 5. The front wall and the bottom of the mirror box are smaller in order to create an open notch. This allows to design a lower rocker box and let the air circulate and accelerate the primary mirror cooling. For storage, the mirror box must accommodate the secondary cage with the focuser.

Figure 6. The mirror cell detail. The front protective screws were later moved to the sides, the sling was installed on them (not shown).

Figure 7. Attachment of the upper part of the truss tubes.

Figure 8. Attachment of the lower part of the truss tubes.

Figure 9. The truss tubes storage and tube parts connection (inset).

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Astronomy TECHNOLOGY TODAY

ical collimation bolts. Instead, there are only two adjustable shoulder bolts that can regulate the height of the two back-side triangles floating on the hinged metal bars (see Figure 6). Back-side triangles can be positioned above or below the third, front triangle which position is fixed on an angle bracket. The collimation bolts go into threaded inserts that are installed through the plywood. The convenience of frontal collimation is exceptional – one can look through the focuser and turn the knob at the same time. To support the mirror while in transport, I placed four 3-inch screws around it. They have no heads and are wrapped in soft plastic tubing. The protecting mirror cover rests on them during transport, while the telescope is set up, and folded down. The cover is a piece of laminate with a thin foam ring attached to it that protects mirror edges from damage. An old backpack strap serves as a sling to hold the mirror in place and prevent tension.

Designing the OTA Before building the rocker box, one should have the complete OTA made first. In order to do that, the length of truss tubes must be known. First one needs to figure out the distance from the mirror face to the center of the focuser hole using the following formula: D = FL – (ID / 2) – FPT – FH – AFT [Where: FL = focal length, ID = inside diameter of secondary cage, FPT = focuser plate thickness, FH = focuser height, fully racked in, and AFT = additional focuser travel of 0.5 inch to 0.75 inch].

Then half of the UTA height (but only if one puts the focuser exactly in the middle between the rings!) and the distance from mirror face to the top edge of the mirror box at corners are subtracted from D. One needs also the distance from the middle of the wall top edge to a truss tube mounting strap on the same wall. Once the two sides of a right triangle are known, the length of the third one can be calculated. This is the truss tube length.

Truss tubes are connected to the secondary cage by simply stringing them onto 1.25-20 bolts, which are mounted on a 0.5-inch wide, 1-inch by 1-inch angle bracket with two nuts and a washer (see Figure 7). The tubes have holes drilled through their upper ends. Once in place, the tubes are fastened with threaded hole knobs. The two mounting screws on each side are parallel to each other. The washer and two nuts are used not only to hold the bolt in place but also to position the truss tubes properly, so they stick out 0.25-inch beyond the UTA edge.

This solution is not the most elegant, but it makes mounting the tubes’ lower ends much easier, because the tubes do not have to be tilted towards the optical axis. The knobs sit on the bolts while in storage and they fit into the mirror box nicely.

Truss tubes are connected to the mirror box by simple pipe straps (Figure 8).

One part of each strap is permanently fixed with a screw. The other part is fixed with a threaded stud knob that goes into a surface threaded insert. There is an additional nut raising the knob slightly, which prevents its arms from bumping onto the strap bend. It is crucial that the inserts are tapped in well and enforced with epoxy, otherwise they will be pulled out while tensioning the clamp. To hold tubes at the same position, there is a sturdy angle bracket installed in each corner of the mirror box. Position of threaded inserts is determined and marked after assembling and adjusting truss tubes in complete OTA. In order to fit truss tubes into a chest, they were cut in half and connected using the tube connectors (Figure 9). It’s essential to make a precise, clean and

A CHEST NEWTONIAN FOR TRAVELERS square cut – a tube cutter is a right tool for the job. To prevent tube ends from crushing and to make stable connection, a couple of washers can be used between the parts. It takes some time to assemble them, so it is not the most convenient solution. One could consider some kind of telescopic tubes, like fishing poles or wheeled luggage handle bars, which can be extended and collapsed in no time.

I like physically balancing the OTA to find the balance point. In order to do it, I place a completely assembled OTA (including a finder and an eyepiece) on a sturdy dowel, like a seesaw. After the balance point is determined, one can figure out the diameter of altitude (alt) bearings and plan the height of the rocker box and the base. One way to do it is to cut bearing dummies out of cardboard or Styrofoam and try them on. The alt bearings do not have to be half circles in order to observe at horizon and slightly beyond zenith, since Teflon pads are usually spaced around 70 degrees apart. On one of the alt bearings, an extension spring can be mounted, in case of balance problem. The bearings are attached to the mirror box by two threaded stud knobs and strong threaded inserts that go all the way through the walls (Figure 10). The laminate strips are attached with some contact cement.

The Rocker Box and Base One needs to take some time to design the rocker box and the base. The bearing size will only partially determine their dimensions. Both these elements will form a chest that has to accommodate all the elements of the telescope.

Besides the mirror box with the secondary cage in it, you need space for alt bearings on one side and truss tubes on the other (Figures 11 & 9). The front and end walls of a rocker box cannot be too high, because the mirror box will bump into them or/and placement of the bearings will be awkward. These walls should not be too low either, because the rocker box will lose its rigidity and the base walls will be consequently too high and possibly unstable. The rocker box should be the internal width of the mirror box, plus 0.25 inch to allow smooth motion and prevent mirror box and rocker box walls from rubbing onto each other. The elements’ length is determined by the alt bearing diameter, so they can fit in for storage.

An azimuth bearing is made of a 14-inch diameter circular piece of Ebony Star laminate on the rocker box and four PTFE pads on the base (Figure 12).

The laminate is attached using contact cement and the PTFE pads are fastened with screws in predrilled holes, so their heads are well hidden. The base contains a threaded insert in the center; the rocker box has just a rough opening of bigger diameter. The bearing bolt is actually a shoulder bolt of the same type as used in the mirror cell collimation system (Figure 6) – it is slightly thicker in its upper, unthreaded part. This upper part goes snugly through the rocker box opening. The bolt is then tightly driven all the way in the insert in the base so it will not move while in use. This solution performs very well.

To be able to set up the telescope on uneven terrain, four soft-rubber legs are attached and they passed the in-field test on a gravel road and my lawn. The front and back walls of the rocker box must be cut to fit those legs. Also, the side walls of the base must be cut to fit the PTFE pads of altitude bearings installed on the rocker box (Figure 13). They should be cut at the end, once you’re sure the pads are spaced properly. To protect the telescope from damage, corner protectors should be used. To keep the telescope closed and its contents safe during

Figure 10. Altitude bearings. One of them can accept an extension spring mount as a virtual counterweight.

Figure 11. Rocker box will accommodate alt bearings and the mirror box with the secondary mirror cage in it. There is still some space left for a shroud and other equipment.

Figure 12. The azimuth bearing parts are the outer walls of the chest

Figure 13. The legs and the Teflon pads should fit into notches. The latches are used to secure the chest contents.

Figure 14. Xena approves the chest size.

Astronomy TECHNOLOGY TODAY

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A CHEST NEWTONIAN FOR TRAVELERS transport and carriage, I used four latches – two on the top, and two on both sides – to allow the chest stand in vertical position.

Wood needs to be stained to protect it from moisture. I used three coats of polyurethane, then I also blackened the inside of the mirror box with spray can paint. A hard lesson to learn was to figure out that wood filled holes look really bad after staining. I guess it’s better to leave these shiny screw heads alone, or maybe use some kind of plug later.

The telescope performs exceptionally well – it is sturdy, it operates without effort, and stays at set position, no matter what is in the focuser. I don’t own any of those very heavy eyepieces, but I suppose I would use an extension spring as a virtual counterweight, as mentioned earlier. I like the advantage of open OTA and no air currents crawling in the tube.

I already tried the telescope under dark skies of Green River Wildlife Area, near Dixon, Illinois, and was very happy about the outcome. My secondary mirror dewed up though, so I guess it’s time to get 12-volt hairdryer and a shroud. Somehow, the primary mirror stayed

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dry all night, despite heavy moisture in the air that had others fighting dew and wiping corrector plates every five minutes. Best of all, I am still amazed how much space I have left after packing the scope into trunk of my Corolla.

What don’t I like? Becoming a master of nightly collimation is one thing – it’s quite annoying. My previous, split-tube Dobsonian didn’t have to be collimated for months. I believe it’s an issue for any truss tube telescope.

The telescope weight could be a problem too.

The height of the secondary cage and width of its rings could be further decreased to reduce dimensions of the rest of the elements and overall chest size and weight. The solid construction makes the scope very sturdy, but the chest is quite heavy if it has to be carried very far. This problem could be partially solved by cutting some wood pieces out of walls, which would be good opportunity to show off some artistic skills. I have considered it for a while, but I store my telescope in a garage and don’t want dust, moisture and insects to get in, although now that it’s a scope chest, I could easily fit it in my bedroom closet.

CHEST NEWTONIAN FEATURES Primary mirror Handmade 8-inch(208mm) f/5.8, Beral coated.

Secondary mirror 1.54-inch (minor axis).

Mount and truss-tube materials 1/2-inch Baltic birch plywood, 3/4inch OD aluminum poles, Kydex Bearings Virgin PTFE on Ebony Star laminate.

Dimensions after folding 20.5 inches x 15.5 inches x 11.5 inches (cm: ~ 52 x 39 x 29).

Weight 35 lbs (16 kg).

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ASTRO TIPS tips, tricks and novel solutions

Online Forums – Ask and You Shall Receive

By Gary Parkerson When we're stumped for a quick solution to a specific astro-tech problem, a growing number of us turn first to online forums.

Indeed, these virtual communities are often the best sources of inspiration. Whether your goal is specific information, or you just want a place to visit with like-minded friends, it's worth investing some time in researching these resources.

ATT's most consistent contributor, Erik Wilcox, has joined with others to create the new astro-forum, Starstuff (starstuff.hqforums.com/). It's powered by phpBB and the resulting format is very easy to navigate.

Starstuff is designed to offer an intimate, laidback setting and Erik invites you to give it a try. We recently posted a general plea for astro-tips there and netted some interesting ideas. I can't cover them all in this single column, but here are a couple of my favorites for now.

Alvin Huey, author of the popular “At the Eyepiece” observing guides (www.faintfuzzies.com), was among the responders.

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

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Alvin admitted that more than one of his fellow “TAC-SACers” (The Astronomy Connection of Sacramento) have taken to drilling 2- and 1.25-inch holes in the “paint” trays of observing ladders, so they don't have to carry eyepieces in their pockets or repeat vertical trips between eyepiece case and focuser. Some, like Alvin, also Velcro flip-top filter cases to the tray for convenient, safe storage of fragile filters while viewing.

Darrell Lee reported that he has strapped chemical hand-warmers to the back of his Orion Intelliscope Computer Object Locator when its LCD display grew a bit sluggish and dim under very cold viewing conditions and recommends that all coldweather observers add chemical handwarmer packs and rubber bands to their astro-emergency kits. In response, Alvin confessed, "I got desperate one night and taped two [chemical] hand warmers on the back of the secondary of my 30-inch Starmaster. It worked!"

So to summarize this month's tips: (1) Keep plenty of chem-pack hand warmers on...well…hand. When it's very cold out, you won't have to choose between warm

hands and warm equipment – your hands will thank you. (2) Buy or borrow 1.25- and 2-inch hole-saws (but be sure to remove your viewing helmet before drilling it). Although you'll soon find many horizontal surfaces that would look better with a functional, yet artful Swiss-cheese motif, don't bet on convincing your mate of that! (3) Invest in spare flip-top filter cases and Velcro them liberally (that viewing helmet might be a good spot for some as well). (4) Sample online astro-forums; you just might find one that feels like home. And finally, (5) while the viewing helmet was a bad joke, the more I think about aging observers climbing ladders in the dark...

Alvin's more functional "paint" tray.

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