Sept10

ASTRONOMY

TECHNOLOGY TODAY Your Complete Guide to Astronomical Equipment ATM LINE IN THE SAND • PEMPRO PERIODIC ERROR MANAGEMENT PROFESSIONAL GERD NEUMANN 10-MM RONCHI EYEPIECE • THE IMAGING SOURCE’S DMK 41AU02.AS CAMERA 1800DESTINY CURVED VANE SPIDER • LUNT SOLAR SYSTEM LS152 • DIY DESICCANT CAPS UNDERSTANDING THE CRITICAL-FOCUS ZONE OF A FAST APOCHROMATIC LENS

Choosing that “GEM” of a Mount!

Mount Images Not To Scale!

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Zeiss, Meade, Celestron, Takahashi, Stellarvue, Vixen, Lumicon, Denkmeier, Vernonscope, Lunt, GTO, Thousand Oaks, JMI, Pentax, Sky Instruments, Proxima, Skywatcher, Coronado, Orion, Explore Scientific, Farpoint Labs and Many More!

Contents Cover Story: Pages 35 - 39 Dr. James Dire’s article on choosing a German equatorial mount (GEM) provides his thoughts on what we should consider when selecting GEMs for specific applications. In celebration of that theme, the cover pictures five popular GEMs that offer extreme ranges within the payload-capacity and style spectrums, each of which is also illustrative of the remarkable values offered by the current astronomy technology market.

The background image of M42 was captured by Dr. Dire using an SBIG ST-2000XCM CCD Camera (-10°C) and a Stellarvue SV-105 105-mm f/6.2 apochromatic refractor on a Parallax HD150 mount, with a total exposure time of 30 minutes (3 x 10), and post processing in CCDOpts, CCDSoft, and Photoshop.

Largest of the pictured mounts is the Astro-Physics el Capitan, conservatively rated for 300 pounds, not including counterweights. While el Capitan is the largest of A-P’s production mounts, the Mathis Instruments MI500 is that company’s smallest production mount, having a net carry capacity of 180 pounds (its MI1000 GEM is conservatively rated to 480).

Also pictured is Celestron’s CGE Pro, one of its newest production mounts and also its largest, boasting a payload of 90 pounds. iOptron, best known for its popular and innovative alt-az go-to mounts, recently introduced its first premium equatorial mount, the iEQ45 GEM, with a target payload of 45 pounds. Rounding out the field is Orion’s Sirius EQ-G, which fills a critical niche among mid-capacity mount options with a payload of 30 pounds.

Industry News 15 WORLD RESOURCES INSTITUTE Suburban Sprawl Encroaching on Protected Areas in the Southern United States 16 AG OPTICAL New Company Offering High End Newtonian Astrographs and Astrographic Dall Kirkham Telescopes 18 TEETERS TELESCOPES Several Upgrades to Telescope Line

In This Issue 12 Editor’s Note ATM Line In The Sand

By Gary Parkerson 35 Selecting a German Equatorial Mount GEMs are Just as Popular Today Among Amateur Astronomers as They Were Nearly Two Hundred Years Ago.

By Dr. James Dire 40 PEMPro Periodic Error Management Professional Software to Correct Your Mount’s Periodic Error, Polar Alignment and Backlash.

By Bob Keyser

56 Understanding the Critical-Focus Zone of a Fast Apochromatic Lens Optimum Imaging Results Require Extreme Focus Accuracy

By Steve Luce

19 CELESTRON Teams Up With ScienceForCitizens.net

68 Lunt Solar System LS152 Modular Design, Ease of Use and Cutting Edge Technology

By Stephen W. Ramsden and Brian Stephens

20 EQUATORIAL PLATFORMS Delivers 30-inch f/3.3 SlipStream Telescope

19 CATSEYE COLLIMATION Clip-on Red LED Light

72 Astro Tips, Tricks & Novel Solutions DIY Desiccant Caps

By Joe Campbell

46 Gerd Neumann 10-mm Ronchi Eyepiece Testing Optics Just Got Easier!

By Erik Wilcox 48 The Imaging Source’s DMK 41AU02.AS Camera Planetary Imaging Made Simple

By Dave Snay 53 1800Destiny Curved Vane Spider No More Spikes!

By Erik Wilcox Astronomy TECHNOLOGY TODAY

9

Contributing Writers

Contents New Products 22 SCOPESTUFF New Products Abound

Joe Campbell works in the Information Technology field by day pushing bits and bytes around the world. However, on clear nights he can be found collecting photons from far off stars, while on cloudy ones he passes the time building things to do it better next time around

Dr. James Dire has an M.S. in physics from the University of Central Florida and a M.A. and Ph.D. from The Johns Hopkins University, both in planetary science, and is an associate provost and a professor of physics and astronomy at Gardner-Webb University in Boiling Spring, N.C. He has played a key role in several observatory projects including the Powell Observatory, which houses a 30-inch (0.75-m) Newtonian, rebuilding and installing an 8-inch (0.20-m) Alvin Clark refractor in a new observatory built for it at the Naval Academy, and was the first director of the Coast Guard Academy Astronomical Observatory in Stonington, CT, which houses a 20-inch (0.51-m) Ritchey-Cretien Cassegrain telescope.

Bob Keyser is a retired radiation effects scientist who has been enjoying an intense involvement in amateur astronomy for the past twelve years. And, while appearing to be normal in other respects, he has been bitten by the astro-photography bug and loves to play with the gear and software.

24 EXPLORE SCIENTIFIC Introduces Fisch Image Lab Software 25 ORION TELESCOPES AND BINOCULARS New Wide T-Rings 25 APM AMERICA New Generation Herschel Wedge

Steve Luce is a professional artist who has a degree in computer science with minors in mathematics and physics. He has studied optics most of his life and his work experience is in the engineering of large medical systems such as cyclotrons, linear accelerators, MRI and CT systems. He has both academic and work experience in electron, proton, and optical beam alignments. He has been involved in amateur astronomy since high school mainly with refractors and astrophotography and built a working spectroheliograph as a high school science fair project.

26 ASTRO-PHYSICS Introduces a Variety of New Accessories 28 ASTROHUTECH Borg 71FL Flourite

Brian Stephens is an accomplished engineer with vast experience in designing and making narrowband solar telescopes and filters. Stephen Ramsden (pictured) is the Executive Director and founder of the nation’s largest privately funded solar astronomy outreach program-The Charlie Bates Solar Astronomy Project (501c3)-in Atlanta, GA. It was named in memoriam to a longtime friend and colleague Charlie Bates. The program has seen over 130,000 kids and adults in the US in the last three years and he routinely speaks and displays the scopes at major events around the country. For further information or to contact Mr. Ramsden please see www.charliebates.org.

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

30 ATIK USA New EFW2 Motorized Filter Wheel 31 VIXEN OPTICS Several New Product Offerings

Erik Wilcox lives off the grid on the Big Island of Hawaii, and has been observing for over 20 years. When he’s not viewing from his dark backyard sky, he works for a natural foods chain, and spends his spare time hiking, kayaking, snorkeling, and performing music. He also runs the astronomy forum at: www.starstuffforums.com.

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Astronomy TECHNOLOGY TODAY

32 MERIDIAN TELESCOPES New URECELL Mirror Cell 32 MEADE INSTRUMENTS New Coronado SolarMax II

The Supporting

CAST

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Tele Vue Optics www.televue.com page 8, 73 Teeter’s Telescopes www.teeterstelescopes.com page 41 Unihedron www.unihedron.com page 62 Van Slyke Instruments www.observatory.org page 33, 55 William Optics www.williamoptics.com page 2 Wood Wonders www.wood-wonders.com page 42 Woodland Hills Telescopes www.telescopes.net page 24

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ASTRONOMY

TECHNOLOGY TODAY

Volume 4 • Issue 5

Editor’s Note

Sept. - Oct. 2010 Publisher Stuart Parkerson

Managing Editor Gary Parkerson

Associate Editors Russ Besancon

Art Director Lance Palmer

Staff Photographer Craig Falbaum

Web Master Richard Harris

3825 Gilbert Drive Shreveport, Louisiana 71104 info@astronomytechnologytoday.com www.astronomytechnologytoday.com Astronomy Technology Today is published bi-monthly

by Parkerson Publishing, LLC. Bulk rate postage paid at Dallas, Texas, and additional mailing offices. ©2010 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.

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Astronomy TECHNOLOGY TODAY

Gary Parkerson, Managing Editor

ATM LINE IN THE SAND! In the last installment of this column I discussed reader demand for more ATM coverage and in so doing mentioned one of my favorite discontinued publications, Telescope Maker.

Judging from feedback generated by that note, many of you miss TM and even more of you than we realized are anxious to see more consistent coverage of ATM projects in these pages. And we are indeed working to bring that to you.

Several such articles are already in the works, but ATM projects being what they are, the first of those may not appear until 2011. Meanwhile, if you are working on a project or have a tip or trick that you would like to immortalize in these pages, please let us know. You can contact me directly at gary@astronomytechnologytoday.com.

Among the article series planned for next year is one that will focus on design, construction, and optimization of Newtonians, both classic and Dobsonian. Frankly, it’s something I’ve wanted to do since the inception of ATT and it’s high time that we get around to it! Planning coverage for 2011 (the fifth publication year for ATT) reminds me that, despite my fairly constant immersion in the subject of astronomy equipment, my principal scope is still the same 10-inch classic Newt that I favored before ATT was even conceived – a scope that has not seen significant modification during the life of this magazine. I suppose that is testament to the quality of its design, construction, and components and could be explained with the if-it’s-not-broke, don’t-fix-it excuse,

but given the remarkable recent advances in materials, finishes, and key components, it’s an unjustifiable state of affairs. Consider this my line-in-the-sand commitment to making my own contribution to ATT’s ATM coverage in 2011.

The old scope currently consists of a 10-inch f/5.6 full-thickness primary carried by a traditional Novak 9-point floatation cell. Although the cell holds collimation well and allows ample air circulation, adjustments are not tool-less as it is currently configured and its design adds little to the structural stiffness of the scope’s solid tube. I’m anxious to explore off-the-shelf primary cells currently offered by this market and to even research design and construction of a custom cell. Now that CAD programs are so easily affordable and, more importantly, actually usable by the uninitiated like me, and with custom CNC-machining services available in most local markets, such custom-crafted scope components are no longer out of reach of us mere tinkerers.

The existing solid tube of my old scope was constructed by hand laying fiberglass over a 12-inch concrete-form tube, the interior of which was then lined with cork and painted flat black. The good news is that the resulting tube is tough and stiff, very dark inside, keeps internal temperatures admirably stable, holds fasteners well, and is easy to cut or drill as occasion demands. The bad news is that the tube is also very heavy. Its exterior is painted gloss white and, although the color fits my image of how a classic

Newt should look, there have been many nights that I wished the white finish did not reflect so much ambient light into my dark-adapted eyes. I’m therefore equally anxious to explore off-the-shelf and custom-crafted solid- and open-tube options – even carbon fiber.

The spider+secondary-holder assembly is also a Novak, consisting of a classic 4-vane spider and shrouded holder. The Delrin base of the holder cracked years ago and my epoxy attempts at repair have left the holder increasingly unstable to the point that I’m adjusting collimation several times a night now. So, I’ll also experiment with optional configurations for replacement of the secondary assembly.

Ditto the focuser, a two-speed Crayfordstyle that is still very competent, but not as much so as more modern interpretations of the Crayford design.

The scope is presently carried by a German equatorial from a vintage Meade 16-inch Starfinder that was modified by upgrade of the bearings in both axes and by replacement of the Right Ascension drive with a 10-inch Mathis gear assembly controlled by an old Lumicon Digital Quarts Star Drive running the synchronous-AC motor of the big gear and the DC motor on the tangent-arm Declination drive. It’s a very stable, but decidedly old-school platform and, while I’ve long assumed I’d eventually replace it, in keeping with this ATM theme I will instead upgrade its drives to Servo with modern digital go-to control now that retrofit systems are so easily within reach of even my modest budget.

I can’t wait to get started on my own ATM project and look forward to sharing it with you in ATT. Meanwhile, we are already working to bring you even more ATM projects in 2011 to compliment our standard coverage of the best the astro industry has to offer. Clear Skies!

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13

INDUSTRYNEWS

WORLD RESOURCES INSTITUTE Suburban Sprawl Encroaching on Protected Areas in the Southern United States

Can’t see the forest for the trees, well that may not be a bad thing. While trees can be an annoyance for those of us in astronomy, forestland represents a buffer for suburban sprawl, which is important to those who seek dark skies.

Organizations like the International Dark-Sky Association (IDA) work towards reducing light pollution with which suburban sprawl is a large contributor and we encourage their support by our readers.

We were interested when we were contacted by the World Resources Institute (WRI) about suburban sprawl in the US. The included map shows suburban sprawl encroaching on protected areas in the Southern United States.

According to the WRI, the Southern US currently contains approximately 39.5 million acres of protected areas—many of them forested—distributed throughout the region. In areas of rapid suburbanization, such as Atlanta, Georgia and Richmond, Virginia, these protected areas are responsible for preserving forestland that would otherwise be lost to suburban sprawl.

Using the maps available at WRI’s www.seesouthernforests.org, users can examine how close suburbanization is getting to protected areas in the South along with other risks facing southern forests. Craig Hanson, director of WRI’s people and ecosystems program, provides outreach to discuss the maps, the changes happening to the southern forest landscape and how private landowners can help save these forests from development.

“At a time when the world is concerned about climate change, fresh-

water availability, the economy and jobs, southern forests are part of the answer,” said Hanson. “The pattern of forest cover loss in this region has been acres here and acres there. Continuous but dispersed change often goes unnoticed.”

According to the U.S. Forest Service (USFS), suburbanization will result in more than 12 million acres of southern U.S. forest being cleared or impacted between 1992 and 2020.

Unless there are changes in the pattern of development that now favors low density housing, strip malls, and road construction, the USFS estimates that from 2020 to 2040, suburban growth will lead to another 19 million acres of forest loss. In total, this loss is approximately 31 million acres, an area about the size of North Carolina.

The USFS also recently released a report that details the impact increasing housing density is having on ecosystem services from forests across the U.S. and identifies the South as a region particularly at risk.

Why should astronomers be concerned? That special place that you enjoy setting up and viewing, while providing great conditions now, may not be so great in the future. At least through organizations like the WRI and IDA, we can be aware and participate in initiatives to keep our skies dark. The WRI’s website is www.wri.org and the IDA’s is www.darksky.org.

Astronomy TECHNOLOGY TODAY

15

INDUSTRYNEWS

AG OPTICAL New Company Offering High-End Newtonian Astrographs and Astrographic Dall-Kirkham Telescopes AG Optical (AGO) is a new company founded by astronomy enthusiast Dave Tandy to craft individually designed, high quality telescopes. Tandy will offer highend Newtonian astrographs and astrographic Dall Kirkham scopes.

Each instrument is fully modeled in NEi Fusion which allows AGO to precisely model each component in SolidWorks 3D CAD and FEA test components critical to the performance of the telescope.

By combining large aperture, fast focal ratio, corrected optics in a lightweight, stiff, and thermally stable carbon fiber tube, AGO has created Newtonian astrographs specifically designed to appeal to the serious astrophotographer offering f/3.6, interferometrically tested optics that use oversize secondaries to ensure full illumination over a wide field of view. Off-axis aberrations are corrected through the use of a 3-inch

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Astronomy TECHNOLOGY TODAY

Wynne corrector providing pinpoint stars over a 50-mm diameter field of view. The Wynne corrector provides 57-mm of backfocus accommodating most CCD camera/filter wheel combinations. The primary and secondary mirrors use enhanced aluminum coatings to maximize light throughput and contrast.

The AGO 12-inch, 16-inch and 20inch astrographs use primary mirrors that have a conical shape (the AGO 10-inch model has a thin, flat back primary mirror that is supported by a 9-point flotation cell). Conical mirrors are lighter than typical flat mirrors and, due to their conical shape, are simple to mount. AGO has conducted extensive finite element analysis of conical mirrors at multiple orientations to ensure that the integrity of the wavefront produced by the primary mirror is maintained.

The tube used for their Newtonian astrographs offers a 0.75-inch thick carbon fiber composite sandwich wall with a Nomex honeycomb core which creates a tube that is much stiffer than aluminum tubes yet weighs half as much. Perhaps the best benefit of using carbon fiber composites for the tube, however, is the focus stability that results from the very low CTE of carbon fiber. Less focus shift means more time imaging and less time spent running autofocus routines.

All of the aluminum parts within the tube assembly are precision machined from 6061 aluminum and are black anodized to provide a dark, wear resistant finish.

Stainless steel fasteners are used exclusively to prevent corrosion. Three 12-volt DC fans are located behind the primary mirror to help the primary rapidly achieve and maintain thermal equilibrium with the

INDUSTRYNEWS ambient air. The speed of these fans can be adjusted as circumstances dictate.

AGO Imaging Dall-Kirkham (iDK) astrographs are high-resolution instruments with excellent off-axis performance. By combining large aperture, medium focal ratio, corrected optics in a lightweight, stiff, and thermally stable carbon fiber tube, AGO has created an instrument capable of capturing stunning images of the universe.

The AGO iDK astrograph line includes a very manageable 12-inch f/6.9 model and two observatory-class f/6.7 models in 16-inch and 20-inch apertures (shown is a ray trace of the AGO 16-inch f/6.7 iDK astrograph). Each model has a conical primary mirror and enhanced aluminum coatings on both mirrors. As is standard with all AGO telescopes, interferometric test results will be provided for both the primary and the secondary mirrors.

AG Optical Dall-Kirkham astrographs provide pinpoint stars (sub six-micron RMS spot size) over a 1-degree to 1.25degree field of view at moderate focal ratios from f/6.7 to f/6.9. This exceptional wide field performance is made possible by the use of a two-element corrector which reduces coma, field curvature and astigmatism to negligible levels.

Each AGO iDK corrector is permanently aligned and has multilayer broadband coatings on each optical surface. Stray light is effectively controlled through the strategic placement of carbon fiber composite conical baffles at the primary and secondary mirrors. As an added measure, the interior of each AGO iDK is lined with a flocking material that is extremely effective at trapping stray light.

Each AG Optical Dall Kirkham astrographs offers a 0.75-inch thick carbon fiber composite sandwich wall with a Nomex honeycomb core which creates a tube that is very stiff and offers excellent focus stability as a result of the very low CTE of carbon fiber.

AGO has selected the Clement low profile focuser as standard equipment for

its iDK astrograph line. This focuser is capable of carrying heavy camera loads and is extremely precise offering repeatable, predictable automatic focusing. Clement’s Robofocus control system allows automatic focusing of stars and perfectly complements an AGO iDK astrograph. Furthermore, the low profile of the Clement focuser allows each AGO iDK astrograph to have a generous amount of back focus (approximately 9 inches) giving astrophotographers maximum flexibility when it comes to selecting imaging train equipment.

The combination of an excellent optical design, top quality components, and careful assembly ensure that each AGO iDK astrograph will provide outstanding performance At the heart of each AGO telescope are precision manufactured optics crafted by master optician Terry Ostahowski.

Ostahowski has over 20 years of experience making precision optics and practices rigorous testing and quality control processes to ensure that each optic that leaves his shop

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will offer diffraction-limited performance.

AGO makes extensive use of carbon fiber and modern core materials which allows them to construct telescope tubes that are incredibly stiff yet lightweight.

Nomex honeycomb core is used to add thickness to the tube walls exponentially increasing the stiffness of the tube. The inner and outer skins of the carbon fiber sandwich consist of a high quality prepreg carbon fiber fabric. Prepreg carbon fiber must cured at elevated temperatures and AGO has built an in-house, large curing oven that relies upon a sophisticated control system to precisely heat, soak, and gradually cool the carbon fiber prepreg according to the temperature profile specified by the fabric manufacturer.

Each tube is finished with a high quality urethane automotive paint. AGO's standard color is gloss black and they can paint tubes in other colors for a small additional cost.

For more information visit www.agoptical.com.

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Astronomy TECHNOLOGY TODAY

17

INDUSTRYNEWS

TEETERS TELESCOPES Several Upgrades to Telescope Line Originally prototyped in 2003 and referred to then as the “Twist Ring” Teeter’s Telescopes has announced its newest “Truss Ring” innovation. The creation of the “Truss Ring” was prompted by their desire to provide customers with a structure that sets up fast in the field and avoids the need of a ladder for the installation of the upper tube assembly (UTA) on longer (taller) telescopes.

Crafted from 13-ply 3/4-inch thickness Baltic Birch plywood, the “Truss Ring” allows all of their telescopes to be stored and transported in two main sections (pictured). With a large enough vehicle, the telescope can be transported in this two piece configuration, with the Truss Ring/Truss Poles/UTA assembly transported horizontally, as can be done with solid tube telescopes.

When users arrive at the observing location, simply place the mirror box/rocker box assembly on the ground and put the Truss Ring/Truss Poles/UTA assembly on top and lock it down using four, large, rubberized 3/8 –inch diameter thumbscrews threaded into four robust 6-tooth T-nuts on the underside of the mirror box’s top baffle. Or, transport the telescope like a typical TrussDobsonian. With the “Truss Ring,” users can store or transport the telescope either way.

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Astronomy TECHNOLOGY TODAY

Teeters has also announced that, due to the closing of Specialty Millwork which was the sole supplier of their wooden components, they have entered into an agreement with Caric Custom Millwork in Chester, New York as its new supplier.

Says Rob Teeter, owner of Teeters Telescopes, “Their experience is extensive, including years of work for large clients in New York City. During a couple of visits to their shop, it was easy to see that they are a busy shop and their tooling is impressive, with the crown jewel being their large CNC Router with associated pumps and dust collection equipment.” He continued, “The owner, Spas Caric, will be taking on the task of programming the CNC Router with my CAD drawings and will personally oversee the assembly of the mirror boxes and rocker boxes after they’ve been cut from the Baltic Birch sheets.”

Teeters is also using a new supplier, John Lightholder of Lightholder Optics in S. Lake Tahoe, California, for their primary mirror cells. All cells 12.5-inch to 20-inch will still us a 18-point flotation, and they will still “tip out” for “tail gate” access to the primary mirror from behind the scope and the standard sling will still be a Nylon strap with the Glatter Cable Sling available as an upgrade.

The most noticeable change will be the material from which the cells are constructed. The new cells are built using aluminum versus steel, which was utilized on the original cells. This will help lighten the load of mirror boxes by several pounds. The cells will feature a “black wrinkle” powder coat finish and will utilize rivets in the corner and joints to provide a rigid frame with no flexure.

For more information visit www.teeterstelescopes.com.

INDUSTRYNEWS

CELESTRON Teams Up With ScienceForCitizens.net Continuing its 50th Anniversary outreach activities, Celestron has announced that it has teamed up with ScienceForCitizens.net, a new website that connects people to research projects and hobbies.

The site's Project Finder offers ongoing activities in a wide range of interest areas, including astronomy, birds, climate, environment, insects, nature, and the ocean. Users can also search based on personal preferences, including locations, how much time you want to spend, whether you want to work outdoors, how difficult or easy the activity is, and whether the project is appropriate for students.

The ScienceForCitizens.net mission is to enable and encourage people to learn about, participate in, and contribute to science through both informal recreational activities and formal research efforts; inspire greater appreciation and promote a better understanding of science and technology among the

general public; create a shared space where scientists can talk with citizens interested in working on or learning about their research projects; satisfy the popular urge to tinker, build, and explore by making it simple and fun for people to jump in and get their hands dirty with science.

Membership is free and easy and all members are invited to upload images and write blog posts about their citizen science exploits.The site highlights member contributions on the home page. If you want to participate in a scientific study or share your citizen science experiences with thousands of others, consider this website.

Celestron will be participating in future contests and promotions with ScienceForCitizens.net, so be sure to check the site out in the upcoming months for a chance to win some of their optical products. For more information visit www.scienceforcitizens.net.

CATSEYE COLLIMATION Clip-on Red LED Light CATSEYE Collimation is well known for providing affordable, practical tools for astronomical use. Their new Clip-on Red LED Light demonstrates this eye on practicality, offering a convenient clip-on twist to a handy accessory.

The rugged aluminum clip-light is equipped with a super bright Red LED for the perfect illumination accessory for night-time use of the CATSEYE Collimation System.

The clip-light features 5000 mcd red LED; narrow 12-degree LED view angle for maximum spot-focused intensity; 360-degree swivel clip which mounts the light to spider, tube, cage, etc.; rubber-

ized-cork-face clip grips for secure scope attachment; push-button toggle on/off; and a single AAA battery is included.

The Clip-on red LED flashlight is priced at $22US. For more information visit www.catseyecollimation.com.

Astronomy TECHNOLOGY TODAY

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INDUSTRYNEWS

EQUATORIAL PLATFORMS Delivers 30-inch f/3.3 SlipStream Telescope Paracorr. Views of Jupiter (a very difficult and demanding object, contrastwise) at 400x were superb with details and subtle color shadings visible across the disk.

Second, the unique features drew attention to the scope. This includes solid, all-metal construction with a durable finish on the aluminum parts, consisting of a dark gray hammertone powder coat on the mirror and rocker boxes, contrasting nicely with the black anodizing on the side bearings,

Tom Osypowski with the 30-inch f/3.3 SlipStream Telescope.

collimation, the entire cell pivots when turning the two collimation knobs. The 18-point back supports for the mirror are calculated by Plop for maximum accuracy. And the fourpoint edge support is designed to carry the mirror without strain or sideways movement.

No testy slings to adjust!

The scope is supported on three sets of dual ball bearings in azimuth and by two long stainless steel shafts in altitude. The oversized alt bearing half-wheels sit on these shafts, which rotate in four pillow-block bearings.

The drive system - motors and controllers - is manufactured by Sidereal Technology. This sophisticated servo-motor drive features slip clutches on both axes, so the scope can be both slewed with the included cordless hand control and also moved by hand at anytime without losing positioning data. Full go-to capability for the scope is realized with the Argo Navis, or with a laptop and planetarium program. Just dial in the object you want on the computer screen, and push a button on the hand control and the scope slews to the target automatically and begins tracking it.

The cordless hand control provides several functions. A three-speed slew in both axes gives complete control over the slewing motions of the scope. You can quickly go from one part of the sky to another with the fast speed, center an object in the field of view with the medium speed, and fine-tune centering at high power or on a laptop screen

A 30-inch f/3.3 SlipStream Telescope, manufactured by Equatorial Platforms, was delivered to a customer at the recent Golden State Star Party (GSSP) in California. The scope received no small attention, Detail of the lower assembly of the scope, showing because of both its size and because of the large altitude wheels riding on 1-inch diameter its unique and handy features. Not to stainless steel shafts. One of the shafts is driven by mention the great views it provided for a belt/pulley arrangement. The stalk carries the Argo Navis computer and an optional netbook. three nights at this very dark sky site. cage rings and other parts.

First, the scope's size drew attention. A The unique low-profile metal mirror box 30-inch is a large scope, and so will always be and exhaust fans in the back of the mirror cell of interest, but this 30-inch was doubly noteallow for quick cool-down of the primary. worthy because of its shortness. At f/3.3 it is Tight fitting covers on shorter than the common 20-inch f/5s that both the front and back commonly seen. This translates to a smaller of the mirror box keep ladder, shorter truss tubes and a generally out insects and dust, convenient telescope to use. The views were protecting the mirror very satisfying, as they should be with a wellduring transport and in corrected mirror, regardless of f/ratio. storage.

Tele Vue’s new Paracorr Type-2 was put The low-profile to good use with the lower power eyepieces, welded-steel mirror cell such as the 26-mm Nagler. Using the supports the glass withParacorr with this eyepiece, the star images out strain. Instead of were tight across the full field of view at 112x. pushing the mirror The rocker/mirror box assembly can be ramped up into a miniAt higher powers (250x and above), the scope supports in and out for van with the included handles/wheels. provided quite satisfying views without the

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Astronomy TECHNOLOGY TODAY

INDUSTRYNEWS that then allow the rockextra cost. er/mirror box assembly to be To sum up, the all metal construction of wheeled around on pneuthe SlipStream Telescopes is strong and matic tires and pushed up durable and the GoTo Alt/Az drive system ramps into vehicles for with built-in slip clutches adds great conventransport. A small van or ience for moving the scope around the sky or SUV works very well for for centering objects, either with the motortransporting the scope. ized slews or with the old-fashion grab-and Finally, there are bunch of push hand method. The GoTos will put an mini-features that make the object in a 200x field of view, and the trackscope friendly to use including of the drive is accurate enough to keep the ing a Feather Touch focuser object centered for long periods. as standard equipment and a If you would like Equatorial Platforms to Rigel Quikfinder is provided custom build a scope for you, please visit www. www.equatorialplatforms.com.

The handles are standard 2x4’s that slip right into the rectan- for centering the two stars gular tubing on the side of the rocker box. The wheels are needed to calibrate the mounted on shorter pieces of the same wood and they too Argo Navis for a slip right into the tubing. Both the azimuth and altitude night's viewing. A movements of the scope can be securely locked down during larger optical finder or transport. guide scope can be with the slowest slew. The speed of all three of easily added to the UTA such as the 80these slews can be independently promm Stellarvue Raptor ED refractor grammed to the user's needs. The hand conshown in the images. trol also includes a built-in red flashlight with A useful ventilation system is proadjustable brightness for chart reading and vided in the mirror cell, with exhaust moving around the scope. fans, rechargeable batteries, and a conAn optional rotating cage assembly trol box to vary the speed of fans and air allows turning the focuser to a convenient outflow. Also, an optional wiring feaplace for strain-free viewing. For large scopes, ture brings power up one of the truss such as this 30-inch, the rotating cage tubes to the UTA for running dew The mirror cell is a welded and powdercoated steel hardware also makes it easy to install the cage heaters and cameras. A rechargeable batstructure. The back of the mirror rests on an 18onto the truss tubes while standing on the tery is also provided in the rocker box to point flotation designed by the PLOP program, and ground. power the drive system and the Argo the edge of the mirror is supported by two dual-pad The SlipStream Telescope also includes Navis. This battery will run the scope for rocker arms. The back of the cell features cooling an innovative transport system. Open ends in three nights on a single charge. A nice fans, batteries, a power box for fan speed adjustthe sides of the rocker box tubing provide custom-fitted black stretchy shroud ment and a thermometer which monitors the temslots for quickly sliding in wheels and handles for the truss tubes is provided at no perature of the mirror and ambient air.

Astronomy TECHNOLOGY TODAY

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NEWPRODUCTS

SCOPESTUFF New Products Abound ScopeStuff posts new stuff way faster than we can ever list them all, so we picked a few here and encourage you to go to their website to see more.

ScopeStuff’s new Wireless GoTo Connection with Bluetooth wireless adapter (Image 1) is now available for Meade LX200 ACF, LX200 GPS & Classic, RCX400, Celestron and ServoCat. Easy to install for a reliable link between a PC and GoTo telescope, no batteries are required for the wireless adapter which derives power from a scope's external power source of 11 to 18 volts DC and draws less than 100 ma. The wireless adapter requires no additional drivers or

Image 1

SFL Quantum Finished Telescopes and SFL Telekit for f/3 - f3.9 optics!

STATE OF THE ART DESIGN Specifically for the special challenges of short focal length optics. New design features Our SFL Quantum finished telescope And SFL Telekit are full featured, easy To build, and highly portable truss Telescope available for 10" - 32".

AstroSystems www.astrosystems.biz

970-284-9471 22

Astronomy TECHNOLOGY TODAY

include finer focus with the standard Moonlight focuser or optional Feathertouch focuser.

Finer thread pitch gives precise Collimation of the secondary and primary mirrors. Optical support components have been stiffened to hold critical collimation, plus more!

software on the PC, and each adapter has a unique PIN number so there's no interference from others on the field.

Just plug the adapter into the scope's power and RS232 jacks, and plug the scope power supply into the adapter. ScopeStuff pre-configures the adapter for each scope type, so installation at the scope is a snap.

The power and data cables are 20 inches long so the adapter can be mounted on a tripod leg, pier, scope base, etc with supplied Velcro and cable clips.

The good old RS232 connectors on laptop computers are a thing of the past, but most new computers have internal Bluetooth wireless interfaces or are inexpensive and easy to upgrade.

The wireless kits are based on Class 1 (up to 100 meter) Bluetooth, with an external rotatable antenna for long range and reliable operation. They conform to specs for Bluetooth RS232 serial devices.

Configuring the Bluetooth on a computer is fairly easy. If the computer doesn't have Bluetooth built in, inexpensive USB adapters are widely available to add Bluetooth to your computer. The owner’s astronomy software must support COM ports greater than COM4, but that’s common on most packages. Windows Bluetooth RS232 port assignments are normally from COM5 to COM15.

If the installation currently uses as RS232 cable to connect to the scope, ScopeStuff’s cable replacement version is plug-and-play and will have the wireless connection running in minutes! Cable replacement adds a computer-end Bluetooth dongle that connects to the D9 RS232 connector on the computer, instead of a long cable to the scope.

The computer-end dongle is pre-configured to automatically connect to the scope-end adapter.

For techies and tinkerers, the Bluetooth adapters are available as an unconfigured kit, with configuration instructions. The

NEWPRODUCTS adapters can be configured via the RS232 interface with an "AT" command set, similar to RS232 modems, and can act as DTE or DCE devices, master or slave. RTS/CTS handshaking is supported, baud rates from 1200 to 230.4K. Power required is 5 VDC, less than 100ma, supplied either from the supplied 120VAC power supply or USB power cable, or from an optional cigarette lighter adapter. 5 VDC power can also be supplied thru pin 9 of the D9 connector.

Two LEDs indicate power and connect status. The factory manual that covers configuration is included. Pricing varies with accessories.

ScopeStuff’s new Filter and Barrel Wrenches (Image 2) grip filters and barrels better than fingers can and have the leverage to remove stuck or stubborn ones. These are much better than tightening filters with wrenches as you can really get them stuck!

Made from black 3/16-inch thick ABS, they won’t scratch your toys. The set is $19.00US. ScopeStuff now offers a Dew-Not Dew Heater (Image 3) for Binoculars up to 10.5-inch in circumference. The ScopeStuff Dew-Not Dew line of heater strips are designed for use in 12-volt systems.

The heater wraps around the tube and secures with a Velcro tab. The outer surface of the heater strip is insulated to direct the heat into the tube, reducing waste of battery juice.

Using polymer thick film resistive heater technology, sixty-six percent of the surface area is heat emitting, meaning even heat distribution and no localized hot spots or burnouts. Because of the increased contact area, Dew-Nots provide more heating with less wattage. Each heater has a six-foot cable with a phono-plug connector that fits the popular controllers from Kendrick, Dew Buster, etc, and can also be powered directly from a 12-volt power source with their optional cigarette lighter adapter. The Dew-Not Dew Heater for Binoculars is $65.00US. Dew-Not Dew Heaters are also available for many other scope applications.

ScopeStuff also offers a dovetail shoe

Image 2

Image 3 Image 4

upgrade (Image 4) for EQ3 type mounts.

Some equatorial mounts don’t use dovetail bars but have tabs that mounting rings attach to directly. ScopeStuff’s #EQ3D upgrades those mounts to accept standard Orion/Synta/Vixen type dovetail bars, and provides a sturdy interface for the dovetail.

The upgrade kit works for EQ3 type

mounts with 5-7/8-inch spaced mounting holes. The upgrade kit includes the bar with the dovetail shoe attached, and all of the stainless steel hardware to attach it to an EQ3 type mount. The kit is priced at $85.00US. For more information please visit www.scopestuff.com.

Astronomy TECHNOLOGY TODAY

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NEWPRODUCTS

EXPLORE SCIENTIFIC Introduces Fisch Image Lab Software

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80mm Triplet ED Apo OTA

www.telescopes.net 24

Astronomy TECHNOLOGY TODAY

Explore Scientific is now marketing the imaging software program, Fisch Image Lab. The program was conceived and written by Greg Fisch who over the past 20 years has developed a number of sophisticated software projects ranging from six-legged, walking robots to CT Scanners. Many projects were involved directly with astronomy or space research.

One of Greg’s best known projects was a program called Epoch 2000. This program was one of the early Desktop Observatory programs. It featured a high-accuracy starmap, telescope control and image processing all in one program. The software was eventually purchased in 1995 by Meade Instruments.

With today’s advanced telescopes and lowcost, high-quality imagers, everyone interested in astronomy can produce breath taking astronomical images using Fisch Image Lab software.

The program’s features include image capture; a sophisticated, easy to use CCD/CMOS imager controller; automatic stacking and rotation that allows imaging with telescopes in Alt-Az configuration; telescope guiding in either Alt-Az or equatorial modes; separate control of main imager and guider; filter wheel support (on selected imagers); automatic bias frame, dark frame and flat field processing while the image is being captured; and images are automatically added into a SQL Database for easy cataloging and searching Fisch Image Lab software also offers high-precision floating-point image processing; 32-bit monochrome; 96-bit color; image prescaler to quickly and accurately fit full-range images into the limited range of computer monitors; all image processing functions work with either RGB or monochrome images; convolution filters (average, Gaussian Blur, Sharpen, Edge-enhance, and many others); additive, average and median combine merge features; RGB merge with luminance and color only function; simple image registration facility built into the merge and RGB merge functions; digital development processing; unlimited undo/redo and many other features.

For more information visit www.explorescientific.com.

NEWPRODUCTS

APM AMERICA New Generation Herschel Wedge APM has developed a new generation of Herschel Wedge for high-resolution white-light solar observing. The APM Solar Herschel Wedge will turn that favorite refractor into a solar telescope.

The mechanical housing is completely enclosed so that the risk of a user burning their hand or clothes is fully removed. Only 5% of the solar light passes through to the eyepiece, removing the risk of injury when used properly with the recommended filters (available separately). The wedge is delivered in a high quality aluminum box with pre-cut foam designed to hold the wedge and filters.

After the prism APM recommends a dark grey neutra-density filter 1.25-inch ND3.0 (1/1000) which blocks most of the 5% light without any risk of cracking. Between the ND 3.0 Filter and the eyepiece APM recommends using a Top-Pol Filter. By rotating the Top-Pol

filter (screwed into the eyepiece barrel) users can infinitely fine tune the level of brightness from photographic brightness to pure visual brightness due to the polarisation with the prism.

APM also offers the wedge alone for those who may already own filters.

APM offers filters from BW-Schneider Kreuznach of Germany for purchase separately for customers who also

need filters.

APM reports that some of their customers have told them of success with lunar viewing with the wedge.

Using the wedge with a polarizing filter only decreases lunar brightness to a level which resulted in far more detailed viewing of the moon’s features.

For more information please visit www.apmamerica.com.

ORION TELESCOPES AND BINOCULARS New Wide T-Rings Orion Telescopes and Binoculars’ new 48-mm Wide T-Rings for 35-mm Cameras are offered in two versions to support full 35-mm format Canon and Nikon cameras.

They are utilized for astrophoto applications using a DSLR or SLR camera and a focal-reducer/corrector lens and convert a SLR or DSLR camera mount to a wide-format Tthread.

These T-Rings offer precision design and functionality and are priced at $20.95US. For more information visit www.oriontelescopes.com

Telescope Accessories & Hardware FEATURING ITEMS FROM: TeleGizmos Covers - Astrozap Dew Shields Dew-Not Dew Heaters - Peterson Engineering Antares - Telrad - Rigel Systems - Sky Spot Starbound Chairs - Smart Astronomy David Chandler - Lightwedge - Baader ScopeStuff Piggyback & Balance Kits Rings, Rails, Dovetails, Cables, ATM, Eyepieces, Filters, Diagonals, Adapters Green Lasers - And MUCH more! www.scopestuff.com 512-259-9778

Astronomy TECHNOLOGY TODAY

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NEWPRODUCTS

ASTRO-PHYSICS Introduces a Variety of New Accessories In response to requests for a cover for mounted polar scopes, Astro-Physics is pleased to unveil their new Polar Alignment Scope Covers. These covers

allow users to keep their polar alignment scope protected while remaining threaded in the mount.

The Polar Alignment Scope Cover for 400/900/1200 mounts (Q12700) has a diameter measuring 3.25-inches at the threads and fits most 1200 mounts, all 400 mounts, and all 900 mounts shipped prior to October 2005. The cover for 900GTO mounts shipped since October 2005 (Q9700) has a slightly larger outer diameter.

A scribe line has been carved into outer diameter of the bell of the Q12700 to distinguish it from the Q9700. This also makes differentiating between covers easy if you are lucky enough to own an

older and a newer 900GTO. If you are not certain when your 900 mount originally shipped, the AP website provides photos of where exactly to measure to determine which part you need. These covers work with all AP polar scope versions except the original PASILL. In the summer of 2009, AstroPhysics began including machined aluminum covers with all newly purchased 2.7-inch field flatteners. For folks who had purchased a field flattener before

The slip-on aluminum cover for the bayonet side of the field flattener has felt along its inside edge. Please note that this cover should be gently pulled to remove it from the field flattener, and not “unthreaded.” It may also be used as a slip-on cover for any accessory with a 3.9-inch outer diameter. In addition to being included in this set and with new flatteners, this cover is available individually as part # A1226F. The threaded aluminum cover has a 2.7-inch female thread for attaching to the focuser side of any 2.7-inch AstroPhysics Prime Focus Field Flattener. It may also be used on any adapter, extension, or accessory that has a 2.7-inch male thread. Astro-Physics has posted a chart on their website illustrating which of their accessories will accept this cover.

Like the slip-on cover, the female threaded cover is available both in the set and individually (part # A1225).

AP’s new threaded Cover for 2.7inch Drawtubes and Accessories is a ver-

then, they are now offering these covers as a set. The set contains two covers, one for each end, which will fit any AstroPhysics 2.7-inch field flattener.

Moreover, they replace the original red cover which was included and provide more substantial protection of flattener optics. Both covers in the set are sold together as part # CSET27FF.

satile cover designed to protect a focuser from gathering dust when not in use. It has the standard Astro-Physics 2.7-inch male threads and can be threaded into any Astro-Physics 2.7-inch focuser, as

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Astronomy TECHNOLOGY TODAY

NEWPRODUCTS well as any other drawtube with that spec. Machined out of aluminum and anodized to match the other focuser components, the front side of this cover also bears the Astro-Physics name engraved on the center flat surface. The cover (part # A1005) may also be used with a variety of focuser adapters, extensions, and other accessories that meet this thread specification.

Close up the sight hole of R.A. axis of your Astro-Physics mount with one of

AP’s sleek, new aluminum machined R.A. Sight Hole Covers. One of these covers is included with all new mount purchases, but now they are available separately for anyone who needs one.

The covers differ slightly in size from each other. The R.A. Sight Hole Cover for 400/900/1200 mounts (M12666) has a 3.25-inch diameter on the male threads and works with most 1200s and all 400 mounts as well as 900 mounts shipped prior to October 2005. The

cover for 900GTO mounts (M9403) has a 3.6-inch diameter to accommodate the redesign of the R.A. axis on the current version of this mount. Comparison photos on the AP website help determine which part is needed.

The Astro-Physics 12-inch Vixen Dovetail Converter (SBD2V) is two plates in one: the top portion is a saddle plate that receives Vixen-style bars and plates. The narrow channel is angled to let you tilt your instrument in. It will accept standard Vixen-style and custom plates that have a 75 degree bevel and are no wider than 1.8-inches.

The bottom portion of the converter boasts the standard 3-inch D-series dovetail, allowing it (and any instrument clamped on top) to be secured in any Dseries saddle plate. Machined of aluminum, AP’s characteristic ribbing on

and 16-inch (SBD16SS) plates have the D-series dovetail on the bottom for use in any D-series style saddle plate.

Both plates accept all but one of the

AP saddle plates on both ends. Now you can run your own instrument or eyepiece field comparisons. Also useful for planning a night of observation where having both a wide field and a long focal length instrument available at a moment’s notice is convenient. The largest thing you might need to swap out is an eyepiece!

For more information please visit Astro-Physics’ website at www.astrophysics.com.

the underside permits this sturdy plate to remain lightweight (2 lbs).

Mount your two favorite instruments at the same time with one of Astro-Physics’ new Side-By-Side Dovetail Plates. The 13-inch (SBD13SS)

Astronomy TECHNOLOGY TODAY

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NEWPRODUCTS

ASTROHUTECH Borg 71FL Fluorite AstroHutech is well known for its Borg line of products consisting of a flexible, and uniquely modular series of high quality refractors with diameters ranging from 50-mm to 150-mm. The new Borg 71FL Fluorite continues that tradition offering 71-mm aperture, 400-mm focal length (f/5.6), premium fluorite optics produced by Canon Optron (Japan), and compatibility with both Mini Borg and Borg Series 80 accessories Portability is an important factor in the Borg system design philosophy. Scope tube

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Astronomy TECHNOLOGY TODAY

diameters are no larger than absolutely required for the light cone, reducing tube weight (but without going to the point of sacrificing stiffness). Lighter scopes themselves make travel easier, but more significantly, they also translate to fewer counterweights and less flexure problems.

Borg tubes can also be disassembled down to short pieces, a convenience for packing, especially for airline trips. And optics, including the objective lenses, can be removed so that only the critical components need be hand-carried. (Removable optics have also proven to be a benefit in humid climates where optical components need to be stored in climate-controlled boxes to prevent mildew damage.)

Modular design is a strong point of the Borg system. This allows the use of many Borg components across several families of telescope sizes, thus reducing production costs and sell-

ing price to the user. This also means more system flexibility to the user.

Upgradability was another goal achieved by modularization. A Borg system can start small and be upgraded incrementally as needs change. Even objectives can be upgraded with minimal impact on the rest of the system.

Photo-visual design with no compromises was a primary concern of the system. Borg scopes fully cover the 6x7-cm frame of the popular medium format Pentax 67 series cameras, and include photographer's extras such as a precise, indexed, lockable (two lockscrews)

NEWPRODUCTS helical focuser and a full range of field flatteners and teleconverters. Also available are a full line of 35-mm camera accessories and visual adapters.

Wide accessory selection is another distinguishing feature of the Borg line. Adapters for virtually all popular accessories (1-1/4inch, 2-inch, SCT, many 35-mm and medium format cameras) are available.

The new Borg 71FL Fluorite comes in seven pre-configured sets starting with the Basic set which offers a Helical Focuser and a number of extension tubes. Other sets enhance the basic setup and include Telephoto, Astro Visual, Fork Mount, Fork

Mount with Tripod, Series 80, and Series 80 F4.7 Astrograph (more information on the configuration of each set is available on the

AstroHutech website).

Borg scopes utilize helical focusers which work by turning a ring to focus as when using a conventional camera (at least in manual focus mode). A true helical focuser works like a camera – when you turn the focusing ring, neither the lens nor the camera (or eyepiece and diagonal) rotate. The only motion is in and out. Some manufacturers implement a pseudo-helical focuser which results in a rotating camera or eyepiece, but Borg focusers are true helical focusers.

The advantage of helical focusers is the fine adjustment possible, in part due to the

fine pitch of the focusing rings thread, and in part due to the large diameter of the ring. In the case of the Borg helical focusers, virtually backlash-free movement and graduated markings on the focusers allow repeatable return to the focus point simply by noting the focus position reading.

A complaint sometimes heard about helical focusers is that they have insufficient focus travel. In the case of Borg scope systems, a draw-tube is an option which allows more than enough extra travel to accommodate accessories.

In addition to being a standard component on Borg scopes, a common use for a Borg helical focuser is to add it onto an SCT or any other scope with a rack-and-pinion focuser. Especially in the case of SCTs this allows for fine focus positioning without the annoying image shift which is often large enough to move a target off a small imaging or guiding CCD chip.

For more information on the new Borg 71FL Fluorite please visit www.sciencecenter.net/hutech/borg.

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NEWPRODUCTS

ATIK USA New EFW2 Motorized Filter Wheel ATIK USA has introduced a new motorized filter wheel, the EFW2, which offers multiple filter capability. This new wheel employs exchangeable filter disks, allowing for multiple combinations, and has large 54-mm openings on both sides.

With these features, the EFW2 can easily support sensors up to full frame (35-mm) format.

The EFW2 also features a sleek design with a slim and lightweight profile. For example, the distance between any ATIK camera and the wheel itself is 0-mm, while still maintaining the possibility of rotating the camera to any desired position.

Total extra backfocus needed is only 22-mm.

On the software side, the EFW2 offers a ASCOM compliant driver, so that any compliant software can control it.

Additionally, the EFW2 works with ATIK’s Artemis Capture software, for easy, simple, and efficient operation.

Features include a closed design which eliminates light leaks even in the presence of light-pollution, a central support that maintains rigidity even when

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Astronomy TECHNOLOGY TODAY

using heavier cameras, magnetic sensors which allow precise positioning without the use of LEDs, a battery power connector (12V cable) and a 3-m USB cable (a universal 110-230V power adaptor is optional).

The EFW2 includes one compli-

mentary disk specified by the customer at the time of purchase. Other disk options include 5x50.8-mm, 5x2-inch mounted, 7x36-mm and 9x1.25-inch mounted.

For more information please visit www.atik-usa.com.

NEWPRODUCTS

VIXEN OPTICS Several New Product Offerings The new Vixen Super Wide Ascot 10X50 offers one of the widest fields possible in a 10x binocular. It is part of the Vixen Ascot Binocular Series which offers portable, compact porro prism binoculars.

The waterproof (Nitrogen filled) binoculars offer bright, sharp images through the Bk4 prism with multi coated optics.

The super wide optics provide a full 8.5 degree field of view. Whether mounted on a tripod or used individually, at only 2 pounds users will enjoy many hours under the stars. It is priced at $159US. The Vixen Space Eye 70 is an “Entry” Level telescope which offers features and quality found on many higher priced optical tubes. From the mount slow motion handles to the diagonal eyepiece holder, this telescope is a nice introductory option for exploration of the night sky The scope features PL20-mm and PL4-

mm eyepieces, altizimuth mount, aluminum two-section tripod, 5x20-mm finder scope, accessory tray, erect image diagonal and weighs 6.8 lbs. It is priced at $129.95US. Now available for pre-order, the Vixen AXD Mount & Star Book Ten offers a sleek design which covers innovative gearing (see cutaway image) for superior performance. Controlled by Vixen’s new Star Book Ten, the AXD combines a wealth of features for the serious astronomer.

The full metal construction of the mount incorporates a bronze 135-mm 270tooth RA Gear and 21 Needle Bearings (13 on RA Axis & 8 on DEC Axis).

With easy to use controls, popular objects appear on the high definition screen and the AXD "SEE-TO" Technology shows the sky before the GoTo sends users there.

With the ability to zoom to any area users can easily find the target object. With more than 270,000 objects, no

computer is needed with the Star Book Ten. The new astro imaging capabilities of the Star Book Ten include integrated video imaging and Video Auto Guiding.

With the Zoom In feature for guiding and planetary observing, users can lock on an object, capture the image, and save it to stack later. With all these features and Permanent PEC, Night Vision Mode, and a 270,000 Database, the new

Star Book Ten with the AXD Mount offers an attractive option for anyone looking for impressive performance from a telescope mount.

For more information please visit www.vixenoptics.com.

Astronomy TECHNOLOGY TODAY

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NEWPRODUCTS

MERIDIAN TELESCOPES New URECELL Mirror Cell Meridian Telescopes has introduced the URECELL Mirror cell for amateur telescope makers or telescope owners interested in upgrading their telescopes, and who are looking for an affordable, easy to install, and easy to collimate primary mirror cell.

The URECELL combines a highdurometer, mercury-free urethane with stainless steel hardware to create a lightweight, efficient, and easy to use design. The urethane material naturally withstands abrasion and has a shore hardness of 80D (a hard hat has a shore hardness of 75D on a scale of 100).

This material can withstand extreme cold and is heat resistant to 200 degree F (94 degree C).

Owners will not have to worry about moisture on their mirror cell since urethane resists moisture and is very resistant to oil and most chemicals. The body

of each cell is molded in color and is black throughout. The bottom side of the URECELL has an attractive gloss black finish and the side facing the primary mirror is machined to a matte finish to avoid any image reducing light reflections.

Consideration was taken into account to provide maximum airflow around the mirror cell for effective cooling of the primary mirror. On the larger size cells, an optional 12VDC cooling fan can be mounted to provide airflow toward or away from the primary mirror.

The URECELL accommodates various thickness primary mirrors and features adjustable mirror clips and shims which provide flexibility for various diameters. Mounting the cell to the optical tube is a snap with a fully adjustable

bolt and nut arrangement to achieve a solid base for the primary mirror.

Instructions are included to provide clear, concise guidance for installing the primary mirror to the mirror cell, installing the mirror cell to the telescope tube and for collimation.

The mirror cell is offered in 4.5" (114mm) - $34.95, 6" (152mm) $39.95, 8" (203mm) - $49.95, 10" (254mm) - $59.95, and 12" (305mm) $69.95.

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range and detail for astronomers who want a powerful, but portable high-resolution Solar Telescope for dedicated visual observation of the Sun as well as high quality imaging.

The SolarMax II is available in a 60-mm version offering 400-mm focal length and f/6.6 focal ratio and a 90-mm version featuring 800-mm focal length and f/8.8 focal ratio. Included is a blocking filter with sub 0.7 angstrom bandwidth filtering, mounting rings,

Cemax 25-mm eyepiece, Sol Ranger solar finder and carry case.

Each SolarMax II is offered in a Double Stacking Etalon. This add on filter reduces the normal bandwidth of a SolarMax II telescope or filter set from the single stack .7A performance to a more restrictive .5A, increasing visibility of surface detail and active regions on the Solar disc.

For more information please visit www.meade.com.

MEADE INSTRUMENTS New Coronado SolarMax II Meade Instruments has introduced the new Coronado SolarMax II, with its new RichView tuning method.

The new SolarMax II allows owners to zero-in on the most precise wavelength of light for each area on either side of the hydrogen-alpha (Ha) band for the highest contrast views of active regions, flares, filaments and other surface features – or quickly retune for spectacular images of prominences on the solar limb. This Ha telescope represents a significant advance for Coronado for tuning range and accuracy.

The patented RichView tuning method works by directly tuning the etalon, the heart of the Coronado Ha filter system, which offers enhanced tuning

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Astronomy TECHNOLOGY TODAY

Selecting a German Equatorial Mount

By Dr. James Dire

In the year 1674, the English scientist Robert Hooke first proposed what we would today call an equatorial telescope mount. The concept was to place a telescope with a rotating axis parallel to Earth’s spin axis and use a clock drive to rotate that axis at the same rate Earth spins, but in the opposite direction.

Then, wherever the telescope was pointed, it would stay centered on the object of interest.

Although there were several crude clock-drive mounts built and used in the 18th century, the first accurate equatorial mount was designed in 1819 by the German optician Joseph von Fraunhofer.

Fraunhofer built a 9.6-inch, f/16.6 refractor that used this mount, which was installed in the observatory in Dorpat, Russia in 1824. This was the first telescope that could accurately track stars.

Ever since, Fraunhofer’s mount design has been known as the German equatorial mount (GEM).

For the next hundred years, large refractors on GEMs were the instruments

of choice among professional and amateur astronomers. The size of the optics reached their limit with the 40-inch refractor housed in the Yerkes Observatory in Williams Bay, Wisconsin, which also uses a GEM. GEMs have their famous “T” shape with the long side of the “T” representing the polar axis, and the cross housing the telescope on one side and counter weights on the other. GEMs are advantageous since they can easily point a telescope to any location in the sky. The biggest disadvantage is the telescope has to be repositioned to the other side of the mount to view objects on the opposite side of the meridian. Fortunately, a properly balanced GEM is easy to maneuver, regardless of size. I found the Yerkes telescope just as easy to manually slew as any small backyard system.

As evident by the number of manufacturers and models, GEMs are just as popular today among amateur astronomers as they were nearly two hundred years ago. With so many choices,

GEMs are just as popular today among amateur astronomers as they were nearly two hundred years ago

Image 1 - The author’s 4-inch apochromatic refractor mounted on an EQ-6 GEM. Astronomy TECHNOLOGY TODAY

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SELECTING A GERMAN EQUATORIAL MOUNT

Image 2 - Dr. Dire poses next to the Cleveland County (NC) Astronomical Society’s vintage Criterion RV-12 Newtonian on its original GEM.

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this article will provide tips in how to select the correct one.

First and foremost in selecting a mount are the size and mass of the optical instrument. If a GEM is used on a tripod, ensure that the optical tube assembly (OTA) will not strike a tripod leg when viewing near the zenith. If so, a pier might be a better choice than a tripod. Second, the mount must be able to carry the mass of the instrument, accessories and the counterweights. Even when balanced, if the mass is too great for the GEM, the polar-axis motor will not be able to properly drive the telescope.

Manufacturers usually publish the payload capacity of a mount. Typically this number does not include the mass of the counterweights, but make sure before buying. Also, manufacturers don’t always agree on the recommend maximum payload. I have seen different brands, but otherwise identical GEMs, probably made at the same factory, where one

SELECTING A GERMAN EQUATORIAL MOUNT company advertises a 25-pound payload, while the other 45 pounds. While both will probably suffice using a 45-pound telescope for visual use, for long-exposure astrophotography, I would not use more than 25 pounds on either mount.

Even for small telescopes, avoid mounts that are not sturdy or wobble when the tripod or pier is tapped. You will be more satisfied with a sturdy GEM rated for a heavier telescope. Plus when aperture fever strikes, you may not have to upgrade the mount.

The smallest GEM I have used came with a featherweight 5-inch SchmidtCassegrain telescope. The mount came with a tiny 6-volt polar axis motor. This mount is lightweight, sturdy and when aligned, tracks quite well for visual use. I no longer own the telescope, but kept the mount to use with a much heavier, longer 4-inch APO when I want a lightweight travel system for observing. This lightweight GEM also goes with me

when I travel overseas chasing solar eclipses. For astrophotography, I use the same APO on a GEM that costs 10 times more.

The main factors to consider in a GEM are: the recommended payload (discussed earlier), total mount weight (be kind to your spine), polar alignment tools, GoTo capability, computer interfaces, power consumption and type (AC and/or DC), size and material of the right ascension (r.a.) and declination (dec.) worm wheels, size and material of the worm gears, diameters of the r.a. and dec. shafts, ease of polar alignment altitude and azimuth adjustments, periodic error and cycle time, clutches, and finally cost.

One of the biggest concerns in using a GEM, is polar aligning the mount. If the mount is not polar aligned, rotating the polar axis, either manually or with drive motors, will not track the telescope’s object. A GEM should have easyto-use altitude adjustment knobs.

Usually there is a scale on mounts to help you dial in the altitude of the celestial pole, which is the same angle as the local latitude. Don’t rely on those altitude scales, as in my experience they can be off by as much as 5 degrees. Likewise, the mount should have opposing azimuth adjustment screws to allow the mount to be adjusted al least 5 degrees, to help point it towards true north, for northern hemisphere locations.

Mounts that allow sighting through the polar axis shaft or that contain a polar axis alignment scope (a small telescope inside the mount along the polar axis) are easier to polar align. For visual observing, I can usually get a decent polar alignment looking through the polar shaft at Polaris as I adjust a mount’s altitude and azimuth knobs. For imaging, a polar alignment scope speeds up the process.

Some computerized mounts come with built-in software routines that aid in obtaining an accurate polar alignment.

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SELECTING A GERMAN EQUATORIAL MOUNT

Image 3 - A current generation, portable GEM holding an 8-inch reflector. Photo by Stuart McDaniel of Shelby, NC.

If a mount is permanently installed in an observatory, a polar alignment scope is not worth the expense. A GEM mount can be accurately polar aligned in a permanent observatory in about an hour using a technique known as the declination drift method.

Originally, GEMs used clock drives powered by falling weights, like in a grandfather clock. Then, until recent decades, they used AC-powered motors.

Today most portable GEMs use a 12-volt DC power source. For field use, a good quality rechargeable lead-acid battery makes the best power source. If AC electricity is available, an AC to DC inverter is required. Make sure the inverter is rated for more amperage than the mount specifies. Otherwise, you risk blowing internal fuses when slewing at the highest speeds. If the mount calls for 5 amps DC, I usually use a 10 or 20 amp power supply. They only cost a few more dollars than a 5 amp supply.

Except for the lower cost entry-level

Utilizing Harmonic Drive the Chronos Mount offers a new paradigm in telescope mount systems.

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Astronomy TECHNOLOGY TODAY

mounts, most GEMs come with GoTo capabilities. These mounts have motors on both axes that can drive the mount to any object in a stored database, once the mount has been leveled, polar-aligned, and the software has been initialized to known star positions (usually two to four stars). GoTo mounts come with a keypad hand controller, which contains the firmware to operate the mount. Additionally, almost all GoTo mounts have a serial port for connecting the mount to a computer. Then with third-party software, the computer can control the position of the mount.

Computer control is advantageous because the computer control software usually has a larger database of celestial objects, and the computer can be located far away from the mount in a climatecontrolled room. I have been known, on a cold winter night, to control a remote GEM used for astro-imaging from my laptop computer sitting on a table adjacent to my hot tub. Ah, the rough life of an astronomer.

The GoTo accuracy of a GEM does depend on several hardware considerations. The main ones are the size of the drive worm wheels attached to each of the r.a. and dec. axes, the number of teeth on each worm wheel, and the resolution of the optical encoders tracking the position of each axes. Generally, the larger the wheels, the more teeth they have, and the higher the resolution of the optical encoders, the better the pointing accuracy of the mount. Most high-end mount manufactures provide these specifications in their advertising. Many companies that sell small to medium sized mounts (under 50 pounds payload) usually don’t provide this information in their advertising.

Some GEMs have knobs that can lock down each axes. These are usually locked down when using GoTo features, but can be unlocked to slew the telescope manually. Others have clutches to allow manual slewing. If the clutches are too

SELECTING A GERMAN EQUATORIAL MOUNT loose, the telescope may drift on it’s own, causing the GoTo computer to lose track of where the telescope is pointed. My advice it to avoid GEMs that allow no manual repositioning of the mount.

If the power source goes down and the telescope cannot be moved manually, the night’s observing session is over.

GEMs used for astronomical imaging, photometry and spectroscopy require more consideration to ensure proper guiding and tracking for long exposures. Due to the nature of worm gears and worm wheels, periodic error (PE) is introduced into the r.a. drive.

If not corrected, a star centered in the field of view will oscillate back and forth in r.a. The amplitude of the oscillation is measured in arcseconds.

The cycle time of these oscillations is usually in minutes. Many manufacturers publish these values for their mounts, or may provide them. In general, the larger the mount’s worm wheels and the more teeth on the wheels, the smaller

the PE will be.

Most computerized mounts come with periodic error correction (PEC).

This is software that can train the r.a. drive to compensate for the mechanical PE. The other choice is to connect an autoguider to the autoguide port on mounts that are so equipped. An autoguider is usually a digital camera attached to the main scope, or a guide scope, that can be used to keep a guide star centered by sending corrections to the mounts r.a. and dec. motors. While PE only affects the r.a. drive, objects will move in declination if the mount is not properly polar aligned. Plus natural scintillation (twinkling) caused by the atmosphere can move guide stars north or south in declination.

Another last parameter I look for in an imaging mount is the amount of backlash present in each drive gear. Backlash occurs when a drive motor switches direction. Backlash is related to how much the drive gear must turn in the op-

posite direction before actually engaging the worm wheels teeth and initiating motion. The greater the backlash, the harder it will be to guide on an object. Some GEMs have built in software that can compensate for backlash.

Finally for the most advanced users, the materials used in the construction of a GEM should be considered. Different metals expand and contract differently during temperature changes. For better performance look for high quality, low expansion metals used for the shafts, the worm wheels and drive gears.

Like any product, for more features and higher quality, you must fork out more money. To find just the right GEM, you must consider your intended use and the features you want, weighed against your budget, before making a final decision. Hopefully, you will be just as excited about using a German equatorial mount as Joseph von Fraunhofer was in 1824 when he saw first light in the Dorpat Telescope.

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Astronomy TECHNOLOGY TODAY

39

PEMPro Software to correct your mount’s periodic error, polar alignment and backlash

By Bob Keyser

This article is about my personal experience using PEMPro V2.6 with a Meade LX-200 telescope. PEMPro stands for “Periodic Error Management Professional.” It is a software tool designed to reduce the amount of periodic error in mounts that have periodic error correction (PEC) capability, along with several other very useful tools.

Background My 8-inch LX-200 Classic (a euphemism for old, circa mid-1990s) is mounted on a Milburn equatorial wedge atop a poured concrete pier in a roll-off roof observatory; it is used for some visual observing but primarily for astropho-

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tography. Periodic error is not a concern for visual work, but certainly is for astrophotography. All mounts have some periodic error, but some, like my LX200, have more than their fair share; as I learned using PEMPro, it is ±24 arc-sec, uncorrected. I always use an autoguider for imaging, which helps correct for PE, but I thought using the scope’s PEC might improve the overall performance of my setup.

What is PEMPro? PEMPro is a program that utilizes a camera, video or CCD, to measure the PE over several worm cycles, create a correction curve, “upload” the correction

curve to the telescope, and then refine the residual PE. In addition, it has utilities for measuring and correcting the drift of a less-than-perfectly aligned equatorial mount, optimizing Dec backlash compensation, and finding a star that is not initially in the field of view of a camera. All of these are useful tools for the astrophotographer, especially one who goes to star parties and so has to sometimes set up in the field rather than always being in the observatory.

PEMPro is available from www.ccdware.com/products/pempro. Like many software products today, it is available as a download and comes with a “manual” in the form of help files. It can be down-

loaded free for a 60-day evaluation period. There is a very helpful forum at http://ccdware.infopop.cc/eve/forums. I made significant use of it to help me figure out why I couldn’t make PEMPro work initially. Ray Gralak was always prompt in replying to my queries and to set me straight as to where I had erred. A permanent license costs $150.

PEMPro works with many mounts and more are always being added. A complete list is in the help file. The “upload” process is very different for this wide range of mounts. Some are programmed by uploading the PEC curve directly into a register in the mount.

Others, like the LX-200 classic, are programmed using a simulation of the manual Learn process. But, instead of a person looking through an eyepiece and correcting for PE by using the guide buttons on a hand box, PEMPro sends guide pulses to the scope via the RS-232 port as determined by the correction curve it has created based on measured PE. This

Image 1 - Basic PEMPro Screen (without Menu Bar: File, Settings, Tools, Wizards, Help)

Astronomy TECHNOLOGY TODAY

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PEMPRO results in a more accurate correction.

PEMPro has the capability to then refine the correction by creating a new correction curve based on the initial PE measurement and the residual PE measured after programming.

Getting Started The first step in using PEMPro is to open the Setup Tab and configure the telescope and camera. Scope setup is done by clicking the Configure Scopes/Mounts button. This brings up a dialog where you name your scope and setup the ASCOM drivers. There is also a Mount Quick Setup Wizard to guide you through this process. (Note: you need to download and install the ASCOM platform and drivers, which initially caused me a problem. I downloaded the latest platform (5.5) and LX200 drivers (5.0.4) and they did not work. Dan Gralak suggested I go back to the 4.1 platform and LX-200 driver and that solved my problem.)

Camera setup is done by selecting the camera program from the drop down list. I normally use MaximDL to control an SBIG ST-7. As soon as I click on Connect Camera, MaximDL comes up and allows me to setup the camera for PEMPro to use. I have also used a Meade DSI camera with Autostar Envisage as the controller. Here it is necessary to open Envisage separately to focus the camera as PEMPro does not bring it up.

The second, very important step in using PEMPro is to run the Calibration Wizard, accessed from the Wizard’s drop down menu. This determines several factors that PEMPro needs to know in order to work properly and verifies the connection from PEMPro to the telescope’s RS232 port. I did not run the calibration before trying to utilize the program at first and, as a result, it did not work and caused me considerable frustration that I could have avoided.

The first step of the Wizard is to slew to a suitable star, near the meridian and

0 degree Dec. This can be done using a planetarium program (my preference) or by slewing to the proper location from within the Wizard.

The second step of the Wizard establishes the image scale (in arc-sec/pixel) and the image roll angle (if the camera is not perfectly aligned on the scope). It does this by turning off the scope tracking and taking a few seconds long image.

You then mark the ends of one or more trailed stars in the image and PEMPro calculates and enters the Image Scale and Angle in the boxes.

Step three of the Wizard verifies that PEMPro can move the scope and determines the scope’s Guide Rate. Select the appropriate Move RA Via option, enter the Image Duration, and click Start.

After the image is taken, the Star Trails Viewer comes up again. Mark the ends of star trails as before and PEMPro calculates the guide rate and enters it in the box.

In the final step, set the Image Duration and click Start. PEMPro will move the scope in RA and Dec and display the result in the Star Trail Viewer when finished. Note the orientation of the L-shaped pattern, select the best match of the eight displayed on this page by clicking on it, and then click Finish.

That completes the calibration process.

Measuring PE and Programming the Correction Curve This is the heart of PEMPro. Before taking data, be sure to connect the scope and camera by clicking the buttons under the Setup Tab. Then click on the Acquire Data Tab. A dialog box will come up warning you to enable or disable PEC, as desired. Since the goal here is to first measure PE without compensation, disable PEC. Set the Exposure Time between 0.1 and 1.0 seconds and the Delay Time to 1 sec. The Image Scale should be set by PEMPro based on the calibration but, if not, enter the calibra-

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PEMPRO tion value manually. Click Start and PEMPro will take a full frame image, select a subframe around a star, and start acquiring data and displaying it in the graph area. It is best to acquire a few cycles (say 4 to 6) of PE data.

After data is acquired, click on the Analyze Tab and/or the Frequency Spectrum Tab to examine the data. But the key element of these pages is the Create a PE Curve button. When clicked on, this brings up another screen that shows the averaged PE data and, after a few seconds of calculation, the fitted PE curve, along with the FFT waveform analysis data. You select the best Drift Fitting algorithm from the drop down list by choosing the one that results in the smallest calculated RMS error. When done, click on the Create PE Curve and Close button. This will save the curve under a file name using the date and time (PemPro-year-month-date-hourminutesecond) with the extension of .ppc and also load it into the Program

Mount Tab. The final step is to click on the Program Mount Tab. Before clicking Start Playback, take the necessary steps to put the mount into record or upload mode. Once this is done, click the Start Playback button. Play back will begin, a yellow shaded area will be displayed in the graph area, and numbers will appear in the table. When a full cycle of data has been programmed, the graph will be completely yellow, the countdown timer will be 0 (or slightly negative), and the lines in the table will change color. Click the Stop Playback button and programming is complete.

You will note that nowhere in the procedure I have just outlined is the Sync Worm Cycle button used. If all PE data are taken, analyzed to create a PEC curve, and programmed into the mount in one session, without turning off or moving the scope, synchronization is not required. PEMPro keeps track of the worm phase internally and starts play-

back at the correct time. If PE data are to be taken and PEC programmed across sessions, then the worm cycle must be manually synchronized before starting playback.

If you are as anxious as I was to see the effect on your scope’s PE, go back to the Acquire Data Tab and take another set of data, this time with PEC enabled.

You should see a significant decrease. My LX-200 went from 48 arc-sec P-P and 11.7 arc-sec RMS before programming to 13.8 arc-sec P-P and 3.4 arc-sec RMS after this initial programming.

But here is where the Refine Tab comes into play. Corrected PE data taken after programming is used to create a new PEC curve by adding it to the original PEC curve. The result is the refined PEC curve. Save this curve and also transfer it to the Program Mount Tab. Then repeat the programming process as above. After refinement, the PE on my LX-200 had decreased to 7.9 arc-sec P-P and 2.24 arc-sec RMS.

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PEMPRO But Wait, There’s More While taking the PE data, I observed that there was still some drift in RA. After TSP, I had used drift alignment to align my scope so that there was no discernable drift in 10 minutes using a Meade 9-mm illuminated reticle eyepiece, my usual criteria for good alignment. So I was surprised to see obvious drift and used the Polar Alignment Wizard to improve the alignment.

To use the Polar Alignment Wizard, click on the tab under the menu bar. The opening screen shows the telescope’s current position, which should be near the meridian and 0 degree Dec as for taking PE data; this is the proper position for assessing the azimuth (RA) alignment. Clicking Next brings up a pre-start checklist of things to do before starting. Then there are several sequential dialog boxes for entering site data, camera data, and determining N, S, E and W; the latter is done by clicking on the same star in three images that PEMPro takes. Finally, you are reminded again to position the scope properly. Then the fun

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begins. Click Start and PEMPro will begin imaging and displaying the data in the drift graph area. After a few points are taken, a trend line will appear on the graph and the movement of the mount required to null out the drift will be displayed (direction and magnitude). PEMPro suggests taking at least a couple of minutes of data to allow the trend to stabilize before making any adjustments and again after the adjustment.

As the mount adjustment is made, something happens that PEMPro doesn’t mention; the star moves and may well move out of the field of view of the camera. When that happens, PEMPro will try to find a new star, but may be unable to do so. So, I always use a well-aligned super-finder, or even my guide scope with an illuminatedreticle eyepiece, to help me move the scope back to the star using the hand box. That way, PEMPro is able to find the star again quickly and continue taking data.

When the trend is reduced to a small value, click Next. The Adjust Mount’s Azimuth dialog comes up to facilitate the

final adjustment. Click on Reference Image and the image will be displayed. Click on the brightest star and PEMPro will draw an arrow to show which direction and how far to move the star, via mechanical adjustment, for perfect alignment.

When finished with azimuth, click Next and PEMPro will then guide you through elevation alignment in the same fashion, though looking at a star in the East or West rather than near themeridian.

I was able to get my RA drift with the azimuth adjustment down to 1 arc-sec in 10 minutes, with a remaining adjustment of less than 0.3 arc-min suggested by PEMPro. The final suggested elevation adjustment was also 0.3 arc-min and the Dec drift is less than 1 arc-sec in 10 min. This is certainly a very useful tool and fun to use.

Clicking the Backlash Tab brings up a screen where you can enter the settings for assessing the scope’s backlash. They are the N/S Move Duration, total Image Duration, Extra Delay Between Moves, and the Dec Movement Method. The durations should

PEMPRO result in a sawtooth waveform with alternating ups and downs (in Dec) as the scope moves in RA. If the waveform has clean, sharp transitions from up to down to up, etc., backlash is low or properly compensated. If there is a flat horizontal part, then backlash is under compensated. If there is a sharp vertical transition (a jump) then backlash is over compensated. Adjust the compensation for best results.

Finally, clicking on the Star Finder Tab will bring up a screen to help find a bright star. It does so by taking a series of images and assembling them into a mosaic. The telescope position and camera information will be filled in by PEMPro. You set the amount of overlap, the image duration, and the maximum number of images in the Spiral Find Star dialog. Click Start and PEMPro will then take the images and display them as they come up. I tested this utility and it certainly works as advertised, though I find it much faster to used a well-aligned finder or guide scope to locate stars.

The Bottom Line I am very impressed by PEMPro. It offers two particularly useful tools for improving the tracking of a telescope: effective periodic error correction and refined polar alignment. It is generally easy to use (if you follow directions), is well supported by the publisher, and, I believe, well worth the modest cost. It will not turn an LX-200 into a Paramount ME but it certainly offers significant improvement. And, it’s just plain fun to use for techies.

I also learned things about my setup that I didn’t know before, like the true image scale and guide rate with the ST-7 on various scopes, which is different from that calculated from scope and camera specifications. Like to just snug the bolts on the equatorial wedge instead of really tightening them down as hard as possible, which shifted the scope enough to actually increase the amount of drift. All useful information! For more information visit www.ccdware.com

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Astronomy TECHNOLOGY TODAY

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Gerd Neumann 10-mm Ronchi Eyepiece Testing optics just got easier!

By Erik Wilcox Image 1

One of the first things I always do upon acquiring a new telescope is test the optics. There are many ways to test optics and many amateur astronomers use the Star Test. However, a star test requires steady skies, a bright star, and medium to high magnification. It also helps to have a scope that is driven so the star stays in the field of view. Lastly, it requires a good deal of interpretation on the observer’s part; in other words, the person looking in the eyepiece has to know what they’re looking for in order to determine the results of a star test.

An easier way to test Newtonian optics is the Ronchi Test. While the Ronchi Test isn’t all encompassing (for example, it won’t tell you the wave error of a para-

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Astronomy TECHNOLOGY TODAY

bolic mirror), it is a simple test that will alert you to many common problems in mass produced scopes. Most notably, these include a turned down edge (TDE), zonal defects, a rough surface, spherical aberration, and astigmatism. A Ronchi test can also be a useful tool when grinding your own mirror.

For many years, I’ve carried a simple Ronchi film-strip tester in my eyepiece case. A good example of when it came in handy was during a star party several years ago. A friend of mine that I used to observe with quite often was complaining that his new scope didn’t seem to give very good views when used at higher magnifications. He was planning on sending the mirror in to get refigured, which would

have cost several hundred dollars. I suggested we take a look at it with the Ronchi test. We pointed the scope at Polaris and removed the eyepiece. I held the tester up to the focuser and took a look. The Ronchi test clearly showed deformed lines near the edge of the mirror. My friend saw it clearly as well.

The next time I saw him he had masked the outer 1/2-inch of his primary mirror and suddenly the scope performed much better! Planetary views were now crisp and weren’t “soft” like they had been before. Images suddenly “snapped” into focus, where before the masking it was difficult to find focus at all.

I’d be willing to bet that there are lots of amateur astronomers out there who

GERD NEUMANN 10-MM RONCHI EYEPIECE blame seeing conditions for their scope’s lack of performance when it’s simply a TDE. One of the problems with the “film strip” style testers is that they’re not easy to work with in the dark. They’re flimsy and I’ve dropped mine on more than one occasion; this is a problem especially when it’s cold out or when the observer is wearing gloves. It’s also difficult to hold the strip flat and in the perfect spot while simultaneously looking through the focuser and attempting to defocus the star to get the correct number of lines to show up (four or five lines is what I generally prefer). Over time, the film strip gets creased or damaged easily; mine has several defects despite being stored in the original envelope inside my eyepiece case.

One of the exciting new products from Gerd Neumann (www.gerdneumann.net) is the 10-mm Ronchi Eyepiece. Unlike the cheap “film strip” testers, the Ronchi grating on this product is en-

GRS Jupiter Series 40-inch Dob

tirely contained inside the eyepiece unit. I was very excited to test this product out and it was shipped promptly and arrived in perfect condition.

The Gerd Neumann Ronchi eyepiece is lightweight and about the size of a very short Orthoscopic eyepiece. It’s only 1inch long and could easily be stored in a Barlow lens or adapter inside an eyepiece case (instead of the plastic caps normally used). The Gerd Neumann Ronchi Eyepiece fits in 1.25-inch focusers (or a 2inch focuser with an adapter). Its build quality is very nice, as it’s made of black anodized aluminum. The eyepiece is equipped with a vacuum metalized chrome-on-glass grating, with 10 lines per millimeter.

In the field, I found the Gerd Neumann Ronchi Eyepiece to be much easier to use than the exposed film strip tester. I simply aimed the scope at a star and centered it, removed the eyepiece, and installed the Gerd Neumann Ronchi Eyepiece. I was clearly able to see the lines

from the grating, and as I defocused the scope, the number of lines decreased until I was able to see what I wanted so I could properly interpret the test. The eyepiece came in handy as I had just acquired a used 8-inch reflector. The optics on this scope turned out to be very good, as it showed crisp straight lines across the entire optic. I also tested the Gerd Neumann Ronchi eyepiece on my 16-inch f/4.5 which I know to have great optics, as it has a mirror refigured by Woden/Optic Wave Labs. As expected, the Gerd Neumann Ronchi Eyepiece showed straight, crisp lines in the 16-inch as well.

The Gerd Neumann Ronchi Eyepiece is a handy and inexpensive tester that I feel every amateur astronomer should own. While it won’t reveal every optical problem, it is an exceptional diagnostic tool to have for testing any Newtonian telescope. It’s far better than the film strip testers and will likely last a lifetime.

Visit www.gerdneumann.net for more information.

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Astronomy TECHNOLOGY TODAY

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The Imaging Source’s DMK 41AU02.AS Planetary Imaging Made Simple

By Dave Snay

I recently had the good fortune to meet John Berryman, one of the sales engineers for The Imaging Source, at “The Vision Show” in Boston. This show is not one you find many astro-photographers attending as the target audience for vendors at this show is usually using imaging tools to enhance their manufacturing processes. As such, they don’t usually advertise in astro-photography circles. However, The Imaging Source has chosen to market some of their cameras to those of us that prefer low-light conditions to the bright lights of labs and manufacturing floors.

While I was talking with John over lunch I learned that he has been interested in astronomy and imaging the heavens for a very long time. That interest prompted him to offer their instruments to the astronomy

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Astronomy TECHNOLOGY TODAY

• 1/2 " Sony CCD, progressive scan • 1280x960 pixels

market and incorporate some of the features beneficial to photographing the night sky. I came away from that meeting with a DMK 41AU02.AS camera that I have been using for a few months (New England weather patterns prohibit quick trial periods!) and have had a great deal of success making images of some of the typical Solar System targets.

This is a CCD-based monochrome camera. At first I was skeptical about the likelihood for success in imaging the planets with a camera that required filter changes. I was afraid I’d see too much rotation in the planet to allow proper alignment for stacking. However, I quickly realized that the planets don’t rotate nearly fast enough for there to be an issue. After all, at 3 – 15 frames per second, you capture an awful lot

• Up to 15 images • USB CCD Monochrome Camera

of data in very short order. I found my greatest success with less than five minutes of data for each channel, usually closer to three minutes was sufficient. Anything above that and my poor PC got very tired trying to process all those frames. I still end up with over 2,000 frames to choose from, so there are more than enough moments of good seeing captured to create a great image. Hopefully you’ll agree as I share my results with you.

First up is a close up of the moon taken through my 8-inch SCT, shown in (Image 1). This is an RGB image based on three minutes of video taken using default settings in the capture software provided with the camera (more on the software later). After collecting all three data sets I imported them to Registax 5, the last version made available, and processed according to the introductory

THE IMAGING SOURCE’S DMK 41AU02.AS tutorial provided by the authors of Registax.

I haven’t used Registax in a very long time and the interfaces are completely different, so I took the default values for everything I could until I got to the wavelets section, where I applied a very mild value of “5” for each wavelet. After that it was off to Photoshop CS3 to RGB merge the data sets and then balance the colors. That’s pretty much all I did for all of the images you’ll see in this article. I kept the processing to a minimum to show the quality of the data provided by the camera.

The next image is also of the moon, shown in (Image 2). However it is a full moon image taken through my Stellarvue SV90TF refractor. I had to use a two panel mosaic to capture it all, but I think it was well worth the extra effort. When I printed this image at my local color lab (I work there part time) I clearly heard one of the customers exclaim “That’s the best picture of the Moon I have ever seen!” That was music to my ears and I’m sure the folks at The Imaging Source are even more pleased to hear that. Again, I processed the data very lightly and I’m sure the image would turn out even better with more time in Photoshop, but I’m very happy with the results and I am thrilled with how little effort it required. Stitching the panels together was almost as much work as the rest of it and I’ve gotten a lot of practice doing that at the color lab so I’ve gotten pretty fast.

I only had one chance to photograph Saturn before it drifted beyond my line of sight and it was on one of my first nights out with the camera. I hadn’t had any time to experiment with the capture software or the camera before that night and I was still able to capture enough data to create the image shown in (Image 3). For this one I used my 8 inch’er and roughly four minutes of data for each channel. It is a little soft, but I believe that’s because I was shooting through a lot of atmosphere. The mirrors in my SCT might not be quite perfectly aligned either and we all know that SCT’s are notoriously finicky about proper collimation.

Image 1

Image Capture Software Included with the package is The Imaging Source’s proprietary capture software IC Capture.AS. This is one sophisticated program. One look at the screen shot shown in (Image 4). reveals the type of interface I prefer. There are no long menu searches to find any control you might want. Everything is right there or is in a pop-up menu that is activated by one of the icons on that screen. Bear in mind that these cameras are not intended solely for astronomical use, so there are some functions and options that

don’t apply well for astro-photography.

However, they have no impact on the usefulness of IC Capture.AS’s functionality.

So how well does the program work?

Refer back to Image 4. That is a screen shot of a single exposure that I was able to make within the first half hour of operation on the first night. Being a typical guy, I started everything up without first reading a single line of the documentation other than how to properly connect and power the unit. I had to poke around a little bit to find the “Live” function and then a little more to figure out

Astronomy TECHNOLOGY TODAY

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THE IMAGING SOURCE’S DMK 41AU02.AS

Image 2

Image 3

how to get it to save a video file. See that little red dot located center left in the tool bars? Look like the record button on a video camera? Hit that and you get a pop-up window that allows you to specify all sorts of parameters regarding image capture.

You can change the duration of each exposure by simply uncheck-

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Astronomy TECHNOLOGY TODAY

ing the “Auto” check box next to the “Exposure” slider on the lower right and then moving the slider left or right. Slide it left and you get shorter exposures. Slide it right for longer ones. If you extend the exposures, you will override the frames-per secondvalue shown in the pull-down menu displayed directly above the “Exposure” slider. Shorten the exposure and you’ll use the shorter exposure at the specified frame rate, with appropriate delay between exposures.

You can choose from several file formats for the video capture. Since I used Registax for my processing program, I used avi file format with a Microsoft RLE codec. You may require something different for your workflow. It took me a few tries to find the right one, but it was a simple matter of cycling through each option until I found a combination recognized by Registax. I did this during the day with no concern for the actual image captured – it was

THE IMAGING SOURCE’S DMK 41AU02.AS

Image 4

actually just the inside of the nose piece cover – since all I really cared about was finding a file format that worked for Registax.

Conclusions When I started this project, I was hesitant about the prospect of using a monochrome camera and the required filter changes to generate color images of Solar System objects. I was afraid I would see too much rotational movement in the objects to be able to generate clear images. It turns out that fear was unwarranted. While it is true that long exposures of planets can result in unclear images, each frame within the video capture can be successfully aligned with the next to ensure clean crisp details.

The DMK 41AU02.AS consistently generated good quality data and is simple to use. Like all other cameras I have used

for planetary and lunar imaging, this one performs best when used with relatively short exposures. It is not cooled and its sensitivity renders it subject to thermal noise generation quite easily with long exposures.

Therefore the DMK 41AU02.AS would not be my choice for deep-space imaging.

However, if you are interested in making high quality images of the planets, the moon or comets then you owe it to yourself to put this camera – or any of The Imaging Source products – on your short list.

The Imaging Source cameras support a variety of sensor sizes. The DMK41 utilizes a 1/2-inch sensor, which yields a pretty wide field of view with my telescopes.

If you want higher magnification, it might be wise to consider one of the other options which come with a smaller sensor.

They are all made with very high quality sensors, so they should all perform equally well.

The Imaging source cameras come with C-mount nose and a 1 1/4-inch nose.

Unfortunately for me, my filter wheel requires a T-thread mount, so I had to adapt.

I found a C-mount to T-thread adapter easily enough and used that to attach the camera to my filter wheel. However, if you choose one of their color cameras you can just use the 1 1 /4-inch nose piece, which would then allow you to include a barlow in your imaging train. If you have a 2-inch barlow, then you’ll just need an eye-piece adapter which probably came with your big barlow.

The DMK 41AU02.AS is currently available through several vendors with a list price of $630. This camera is definitely one of the highest quality camera’s I have ever used for Solar System imaging. If you own one if these beauties, you’ll definitely be swimming in the deep end of the astro-photography pool.

Astronomy TECHNOLOGY TODAY

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No More Spikes!

1800DESTINY CURVED VANE SPIDER

By Erik Wilcox

As an avid tinkerer and Newtonian enthusiast, I’ve made modifications to nearly every scope I’ve ever owned. Part of the allure of Newtonians (and Dobsonians in particular) is the fact that they can be improved upon very easily. Flocking, a better focuser, bigger altitude hubs, filing down mirror clips, the list goes on and on. But my favorite and best “bang for the buck” modification to a Newtonian telescope is to replace the straight spider/secondary mount with a 1800Destiny Curved spider.

Most people that use Newtonian telescopes notice the bright “spikes” that shine off every star in the FOV. And many just accept it as part of the tradeoff in using a Newtonian reflector. In fact, one of the points that many refractor users often bring up in why they prefer lenses over mirrors is the “stars with spikes” issue.

A properly designed curved spider eliminates these spikes. Some will say that a curved spider hurts the views; nothing could be further from the truth. It’s true that a curved spider spreads the diffraction out over a larger area, whereas a straight spider concentrates it into a small area (hence, the “spikes”). But a properly designed curved spider makes the diffraction essentially invisible.

A properly designed curved spider will show no “glow” around bright objects or any other effects that can be seen through the eyepiece with the naked eye.

Others may say that a curved spider introduces more material into the light path.

This is not necessarily true either. A typical 3

vane curved spider has about the same material in the light path as the stock 4-vane straight spider that comes installed on most telescopes. It’s also important to remember that the diffraction is a tiny portion of the light that enters the telescope and when it’s spread out, its effects are negligible. However, when the diffraction is concentrated, as it is with a straight spider, the effects are obvious; spikes emanating off of every star. 4-vane straight spiders show four obnoxiously bright

spikes, while 3-vane straight spiders show six slightly less offensively bright spikes. Have you ever looked at Jupiter through a Newtonian with a straight spider when the Galilean moons happen to be lined up in the path of one of these spikes? It’s not a pretty sight. Just because the Hubble Space Telescope suffers from this aberration doesn’t mean that amateur astronomers have to put up with it.

I recently bought a used 8-inch f/5 OTA as a “project” scope. I currently own a 16inch truss dob and a couple of smaller scopes, but I wanted something in the 8-inch range for planetary viewing and casual deep-sky use. This scope is typical of many mass-produced Newtonian’s. The overall build quality is decent and the optics on this scope are actually quite good. This particular scope has a factory installed 4-vane straight spider. The spider mount used in these scopes suffer from several design flaws. Besides the issue with the spikes, this spider uses a “clip” to hold the secondary mirror in place, which covers a portion of the aperture. The mirror is then installed inside of a rigid plastic unit that pinches the entire circumference of the mirror. Finally, installed behind the mirror is a thick piece of foam, which I’ve heard more Astronomy TECHNOLOGY TODAY

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1800DESTINY CURVED VANE SPIDER than one amateur astronomer refer to as “the heat trap.” I was only too happy to remove this unit so that I could install the far superior Destiny Curved Spider.

The spider was shipped to me promptly, as is always the case with 1800Destiny. This is the fourth 1800Destiny Curved Spider that I’ve owned, and Hans, the owner of 1800Destiny Spiders, is a great guy to deal with. Over the years, I’ve witnessed several improvements to his design and the latest version is even better than any of his previous offerings. I have the “Extreme” 1800Destiny 3-vane Curved Spider on my 16-inch scope that is about five years old and it’s an incredible piece of gear. But the new version features collimation screws that can be adjusted by hand (or with a screwdriver), as well as pre-drilled mounting holes and black anodized Allen bolts, so no interior nuts are necessary to install the new 1800Destiny spiders.

Finally, the end of each vane on the latest unit is bent to the exact shape of the OTA where it meets up. This makes the spider even more rigid and also makes sure that the three vanes add up to exactly 180 degrees for optimum performance. As always, all 1800Destiny spiders are finished in flat black and feature a hefty acrylic secondary mount (also flat black) that the vanes attach to. The build quality is absolutely first rate.

Installing a 1800Destiny Curved Spider is very easy for anyone that’s the least bit mechanically inclined and is comfortable collimating a Newtonian reflector. First, I removed the old straight spider from the tel-

54 Astronomy TECHNOLOGY TODAY

escope and set it on a table. I unscrewed the “clip” mount and carefully pried the mirror out of the plastic unit that was really pinching it. Frankly, I’m shocked that I wasn’t able to see massive astigmatism from how badly the secondary mirror was being pinched. For some scopes, foam tape is most often used to attach the secondary mirror and it can easily be removed with a razor blade.

After removing the secondary mirror, I installed it onto the 1800Destiny secondary mount with black silicone. I made three dime-sized dots and carefully set the mirror onto the silicone. The small “dots” of silicone allow the secondary mirror room to expand and contract (unlike the previous method of installation with the rigid plastic holder), and is much preferred rather than smearing silicone over the back of the entire mirror).

Next, I let the silicone cure for 24 hours. This step is very important as you don’t want the secondary mirror to fall off and land on your primary mirror (I say this, ugh, from previous experience!).

Since I had the entire mount out of the scope, I took the opportunity to blacken the edges of the secondary mirror. I did this very carefully with a black Sharpie permanent marker. While a black sharpie is probably a bit more reflective than flat black paint or flocked paper, it is still a large improvement over the unfinished glass, which reflects light rather obviously. And unlike using flocked paper on the edges of the secondary mirror, using a Sharpie doesn’t add any more material into the light path. It’s also quick and easy, unlike paint which would require masking

the front of the mirror to avoid damage to the coatings from overspray.

Next, I removed the primary mirror from the scope. This is important when doing any drilling so that metal shavings and other debris don’t fall onto the optics. Also, as I planned to have the scope upside down at times, I didn’t want risk having the mirror slip out of the cell.

Installing a 3-vane spider in place of a stock 4-vane spider requires the drilling of just two holes. If no drilling is preferred, 1800Destiny also makes a 4-vane curved spider which will bolt right in place. However, the 3-vane is just as rigid and a 4-vane is really not necessary (and adds more material in the light path). Besides, the drilling is easy.

The 1800Destiny spider has a large amount of adjustment capability so I decided to use the stock hole placement. I measured the distance from the end of the OTA to the existing holes. Normally, I would have also measured the circumference of the OTA to determine the exact spots for the two remaining holes I was going to drill; however, in this case, the telescope screws that held the end ring on were in precisely the right spot. So I simply marked the holes to be drilled 3/4inch below the end-ring screws. I placed the 1800Destiny spider on top of the scope to make sure everything lined up; it was perfect.

Using a 1/4-inch drill bit, I carefully drilled the two holes. I then filed away the excess metal shavings and carefully placed the spider inside the scope. The 1800Destiny spider features threaded holes; no nuts to fall onto your primary mirror! This also made in-

1800DESTINY CURVED VANE SPIDER stallation a breeze; I simply lined the holes up and screwed the Allen screws into the holes (Hans even provides the Allen wrenches with the spider!). After tightening the mounting holes, I eyeballed the secondary mirror to make sure it was oriented correctly with the focuser.

Next, I reinstalled the primary mirror.

From there, it was just a matter of collimating the optics. Using a Cheshire tool and a Howie Glatter laser collimator, it took about 10 minutes to get everything lined up perfectly. The only snag I ran into was when I tried to reinstall the dust cover; the middle adjustment “spring” screw (which is a bit longer than the thre secondary mirror adjustment screws) on the 1800Destiny spider was about 1/4-inch too long, and the dust cover wouldn’t quite snap on. This really isn’t the fault of the 1800Destiny mount and wouldn’t likely be a problem on the many scopes. However, my scope has a secondary mount that’s placed extremely close to the front of the OTA, so there’s not much room to work with. The simplest solution would be to simply use a hacksaw to cut 1/4-inch off of the adjustment screw or to install a shorter screw. As this OTA is a used “project” scope, I decided to instead drill a 1/4-inch hole in the exact center of the dust cover!

After doing that, the cover snapped on easily.

By this time, it was getting dark outside and I was in luck! The tropical rainstorm we’d had move through the area earlier had dissipated and the clouds had parted. Beautiful clear skies beckoned to me and I excitedly brought the modified 8-inch Newtonian outside.

I first pointed it towards the southwest where a nice planetary conjunction was occurring. Venus shined brightly, along with Saturn and Mars nearby, and Mercury a bit closer to the horizon. Looking at Venus, I remembered why I like referring to a Newtonian modified with a 1800Destiny Curved Spider as being like an “apo on steroids.” Obviously, there was no chromatic aberration like that seen in all but the most expensive refractors, especially if you were to price one with 8-inches of aperture! Venus showed a

nearly full phase with no spikes, and the sky around the planet’s disk was jet black and well-defined; no “glow” as may be seen with a poorly designed curved spider. Despite being low in the sky, Saturn showed an immense amount of detail at 220X and the rings were nearly edge-on. Mars and Mercury were a bit more of a challenge; Mars is far away right now and Mercury was lost in the horizon.

Over the next few nights, I had the opportunity to observe Jupiter (with good results), as well as many deep sky objects. Even on deep sky, I find the Destiny Curved Spider to be superior to a straight spider. It’s nice to look at star fields and see natural looking stars without tiny spikes coming from each one.

Whether it’s a 4-inch Newtonian or 40inch Newtonian, 1800Destiny has (or can make) a curved spider that will likely be a vast improvement over the straight spider installed on most scopes. As a big fan of Newtonian reflectors, I personally would not own a scope with a straight spider. Amateur astronomers spend thousands of dollars on well-corrected eyepieces to eliminate astigmatism and field curvature (among other things), coma correctors to eliminate coma, even products that correct for astigmatism in the eyes. Yet many just accept the spikes as part of the cost of owning a Newtonian Reflector. It doesn’t have to be that way, and for the price of an inexpensive eyepiece the spikes can be eliminated. Do yourself a favor and contact Hans at www.1800destiny.com and install your very own 1800Destiny Curved Spider; it’s an upgrade you won’t regret.

Astronomy TECHNOLOGY TODAY

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Understanding the Critical-FocusZone of a Fast Apochromatic Lens Optimum Imaging Results Require Extreme Focus Accuracy Editor’s Comment: ATT is proud to present Steve Luce’s detailed analysis of challenges faced in maximizing the zone of critical-focus (CFZ). The graphics that accompany his article are extremely effective in demonstrating factors that affect the CFZ. Unfortunately, appreciation of the significance of these graphics requires comparison of subtle transitions from image to image and, as is often the case, the resolution limits of ATT’s newsprint pages may prove inadequate in reproducing those images. Fortunately, ATT subscribers enjoy ready access to a high-res digital presentation of all articles via the online version of this magazine.

We would also like to take this opportunity to note that Steve Luce, an accomplished professional artist, is not currently employed in astronomy or optical engineering, although he has considerable training and experience in both. We mention this because he is a prime example of the extreme level of sophistication that is typical of ATT’s amateur contributors and readers. As do all “amateurs” who contribute here, Steve merges skills honed in other fields with practical experience with, and self-study of, the tools of astronomy to produce unique insights of value to all astronomy enthusiasts – pros and amateurs alike.

By Steve Luce

I have been studying focus and optical alignment of fast apochromatic telescopes for several years and am extremely impressed with the quality of modern optics, but have also come to believe that focus and alignment are as important as the optics themselves – the best of apochromatic lenses can be reduced to substandard performance by poor focus or collimation. To better quantify the relative importance of focus accuracy, as well as to better understand the role of my Rigel Systems stepper-motor focus system in the precision focus process, I conducted the series of focus tests detailed in this article.

Equipment An APM 105/650, f/6.2 LZOS triplet scope was used in these tests (the APM apo uses the same optics as the TMB 105/650). A non-APM 0.85x flat-

56 Astronomy TECHNOLOGY TODAY

tener/reducer was also tested with this telescope. This flattener/reducer reduced the APM focal length to 552 mm and increased the photographic speed to f/5.27.

Later in this test series, an APM/TS Optics field flattener and the GoldFocus focusing system were used as well.

For a camera, I used a modified Canon 20D DSLR. This camera features a 15-mm by 23-mm sensor and requires a flat-field circle 28 mm in diameter.

APM recommends that a field flattener be placed in the optical path for wide-field astrophotography. This means that any image taken with the uncorrected APM scope using the Canon 20D (or other similarly-large sensor) will be in focus for most, but not all, of the image. The areas not in focus will be at the extreme four corners of the CCD frame.

The non-APM 0.85x flattener/re-

ducer is recommended only for telescopes of focal length up to 600 mm. I cannot stress too strongly that this flattener/reducer specification is out of range for a 650-mm scope. But, the resulting partially-flattened field is t ypical of optical systems used in astrophotography and helps to demonstrate complex focus issues facing today’s astrophotographer.

The tests that I include in this article show that the non-APM reducer produces surprisingly good results – even at 650 mm – and that the Rigel Systems stepper-motor focus system used on the scope does a supreme job of finding the best possible position of the imaging-sensor plane within the focus zone for the triplet.

I also used a Gemini-equipped Losmandy G11 mount and guide system for all tests. The guide camera imager that I

UNDERSTANDING THE CRITICAL-FOCUS ZONE OF A FAST APOCHROMATIC LENS used is made by Orion and the guiding accuracy of the drive during these tests was held to less than one pixel of error.

I should also note that the point of these tests was strictly focus and not image quality. Image development was minimal and performed in Photoshop only to the extent required for best comparison of focus change from image to image. Focus was, in all cases, adjusted with the Rigel Systems stepper-motor control system fitted to the Starlight Instruments 2-inch Feather Touch focuser, standard on the APM scope.

Astrophotography Setup I picked a convenient area of the sky with a single bright star for quick focus of the camera and alignment of the guide system. Once the scope was tracking, I was able to take a series of photos to test the flattener and stepper-motor focus system.

The exposure times were held to less than 30 seconds to reduce star bloat due to atmospheric changes and to minimize guide corrections. The ambient temperature during the tests was 55 degrees Fahrenheit and did not change by more than 2 degrees over the entire test. Thermal changes to the scope and focuser were, therefore, minimal.

The Initial Full-Frame Image Figure 1 is the first of a series of images produced with the APM scope and 0.85x flattener/reducer. At first glance, the image in Figure 1 looks good. However, Figure 2 is a sample from the upper right corner and shows a typical field-curvature error. This corner-star distortion is a form of astigmatism. Because the corners were out of focus (distorted), I picked a corner area to examine focus changes from image to image.

I moved the CCD toward the objective in steps of 25 microns to document the change in the corner star distortion as focus improved. Image 2083 (shown in Figure 2) was the first image of that set.

Figure 1

Figure 2

A Map Of This Study The red-box sample area in Figure 3 is 580 x 400 pixels. I took a sample of the same size and from the same place for each image in this test series. The image numbers are 2083 through 2112 (as assigned by the camera counter) for this focus study and all of the 580 x 400 images are at 100 percent. I also looked at a 200-percent star detail in the corner

(green box) and the center (blue box) of each image.

Image 2106 shown in Figure 4 is from about the middle of the sequence and from a focus position that is approximately 565 microns closer to the objective than that of Image 2083 in Figure 2.

As corner focus improves, the egg shape shortens.

Image 2112 in Figure 5 is a sample Astronomy TECHNOLOGY TODAY

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UNDERSTANDING THE CRITICAL-FOCUS ZONE OF A FAST APOCHROMATIC LENS corners are similar in appearance (or identical, as with the APM) regardless of distortion amounts, the objective is well aligned and the imaging sensor and objective are parallel to each other. This test is very sensitive. (This technique is perhaps the best, quick-test measure of collimation and general optical alignment available to the amateur without more specialized equipment. However, I’ve run across relatively few amateurs who are aware of or use it.)

Figure 3

of corner focus that represents about the best this optical system can produce. The focuser change from 2106 to 2112 is about 70 microns.

By the way, this corner-star optical-

distortion transition point is an excellent place to check collimation. By examining an image in all four corners, collimation can be checked by comparing the star distortion pattern of each corner. If all four

More Detail on Corner Star Distortion As the imaging sensor is moved closer to the objective, the corner-star astigmatism changes in shape from Figure 6 to Figure 7. If the flattener is well designed and compatible with the objective, there will be a zone where the corner stars are round.

Figure 6 is of a corner star out of focus where the sensor is too far from the objective and Figure 7 is of a corner star

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UNDERSTANDING THE CRITICAL-FOCUS ZONE OF A FAST APOCHROMATIC LENS out of focus where the sensor is too close to the objective.

Figure 8 is of a series of star details showing the changing astigmatism in the corners. These are 200-percent images and a rough focus-change of 25 microns per image was used from 2083 to 2108. A fine focus of 5 microns change per image was used for images 2008 through 2012.

The images in Figure 8 are an unfortunate example of a crossover of focus without ever producing a good corner-star shape.

If you look carefully at the upper star detail, you can see the star shape changing from the astigmatism shown in Figure 6 to one of a four-point distortion. This is a corner star on its way to the opposing distortion seen Figure 7. The star is morphing from the Figure 6 shape to the Figure 7 shape without ever being a truly round star. If the flattener was perfect in this area of the image, 2112 would be circular with no flares. This is a common optical problem for the amateur as-

Figure 4

trophotographer. It is also important to realize that these changes are a result of a mere 20-micron linear change of the focuser. For reference, twenty-pound paper is 100 microns thick.

Please also remember that the 0.85x flattener/reducer is being asked to perform beyond its design specifications.

Therefore, this error is not the fault of the triplet main-objective or of the flat-

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UNDERSTANDING THE CRITICAL-FOCUS ZONE OF A FAST APOCHROMATIC LENS

Figure 5

tener/reducer. The combination of the APM objective and this 0.85x flattener/reducer is simply beyond the application ranges specified for optimum full-frame focus performances of each.

A Problem with the Center Star Focus As the Corners Stars Are Focused!

If you look closely at Figure 8 you will see another unpleasant surprise. The

lower set of star photos are from the center of the image and the red arrows show the center star focus getting worse as the corner stars get better. Figure 9 provides a cross-sectional histogram of the Figure 8 center star.

The black curve is a histogram of the 2083 center star and the red curve is the 2112 center star histogram. The FullWidth-at-Half-Maximum (FWHM) value for the 2083 star is 3.70 and the FWHM for the 2112 star is 5.26. The profile curves show that the center of image 2112 is slightly out of focus with respect to image 2083 center – bad news!

The conclusion must be that it is not possible to find a position for the sensor where all stars are in focus with this telescope and field-flattener/reducer combination; the Critical Focus Zone (CFZ) for this lens and flattener configuration is not deep and/or wide enough for the imaging sensor. (This set of histogram curves was generated by ImageJ [http://rsbweb.nih.gov/ij/features.html] and a FWHM plug-in, both suggested to me by Craig Stark of Stark Labs.)

It is important to note that it is nearly impossible to make focuser adjustments of 20 microns or less (1/5 the thickness of 20-pound paper) consistently by hand. I now realize that focus at this level must be done with a stepper motor and these tests serve also to demonstrate the amazing consistency and precision of the Rigel Systems steppermotor focus system.

A Conceptual Illustration of a Fast Apo Field Curvature Figure 10 provides a 2-D illustration of the focus zone of a fast apochromatic lens. The blue area is the curved (partially flattened) focal CFZ of the lens and imaging sensor is positioned at the top edge of the red line that represents it. The sensor will see a focused beam only in the area where the top of the red line is inside the blue area. Areas of the sensor plane (the red line) outside the blue zone are

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UNDERSTANDING THE CRITICAL-FOCUS ZONE OF A FAST APOCHROMATIC LENS

Figure 6

Figure 7

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UNDERSTANDING THE CRITICAL-FOCUS ZONE OF A FAST APOCHROMATIC LENS

Figure 8

seen as out of focus by the sensor. In this illustration, the sensor image is focused in the center and out of focus at the edges or corners of the image. The red line represents the 28-mm diagonal of a Canon 20D’s sensor.

If we could curve the imaging sensor in three dimensions to the match the curvature of the blue CFZ area (as done in Schmidt cameras with film), the image

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produced by the sensor would always be in perfect focus. Figure 10 approximates the focus in Figures 2 and 3 shown above.

The center is excellent, but the edges, or corners, are out of focus.

If we move the plane of the imaging sensor higher – toward the telescope lens – the edges will be in better focus, but the center of the beam will move out of focus. The images in Figure 8 demon-

strate what happens as the sensor is raised or moved closer to the objective. The edges improve, but the center stars move out of the CFZ and slightly out of focus.

Please note that the drawing in Figure 10 is not to scale. In this illustration, the CFZ is enlarged to a depth of about 5 mm – if the illustration were to scale, the blue zone would be similarly enlarged to 1000 cm (33 feet) wide!

UNDERSTANDING THE CRITICAL-FOCUS ZONE OF A FAST APOCHROMATIC LENS

Figure 9

An Interesting Change to the 0.85x Flattener/Reducer – An Improvement!

After running this set of tests, I decided to reduce the space between the flange of the 0.85x flattener/reducer and the imaging sensor. I bought a thinner “T” adapter and lapped the face of the adapter on a precision machined steel surface. The specifications of the 0.85x flattener/reducer instruct that the spacing between the flange of its 0.85 reducer and the plane of the sensor should be 56 mm (+/- 2 mm), and all of the measurements documented above were at that 56-mm spacing.

But, because my scope has a focal length of 650 mm and therefore exceeds the design specifications of that reducer, I decided to try a reduced spacing of 52-mm separation between the reducer’s flange and the sensor plane – a full 4 mm less than the 0.85x flattener/reducer’s specs.

The result of the 52-mm separation was improved corner focus with the 105/650 APM scope, warranting a set of new and very detailed focus tests.

A New Set of Image Tests Figure 11 is a representation of the optical path for my tests. I made a quick analysis of 80 of the 120 images I took (each image consists of an exposure of 30 seconds at ISO 1600). In this focus analysis, I used star FWHM to measure star focus changes and the imaging sensor was shifted 25 microns per image toward the objective through the focus zones of the sequence.

I picked four of the larger stars in the image that fell on a diagonal from the center to the corner of the image and measured the FWHM of each of the four

stars at 80 different positions of the sensor as it moved into and out of focus. The star samples are: Center Star (blue), 30percent Star (magenta), 60-percent Star (yellow), and Corner Star (cyan). A map of the four star locations is shown in Figure 12. All four stars moved through good, but different, focus points as the imaging sensor moved closer to the objective.

Figure 13 is a plot of the FWHM values of each of the four stars as the sensor moved into good focus and out the other side. This chart shows the changing focus-zone as the sensor moves toward

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UNDERSTANDING THE CRITICAL-FOCUS ZONE OF A FAST APOCHROMATIC LENS

Figure 10

the objective. Each of the four selected star focus-zones shown occurs at a different focuser position and each seems to be about 125 to 200 microns deep. As the four stars come into focus, the CFZ is shifting from the center to the corner of the imaging sensor. The CFZ depths are in approximate agreement with the simple CFZ equation for a 105-mm, f/5.3 lens at beam centerline.

The focus difference between the center-star focus (blue line) and the corner-star (cyan line) focus is about 150 microns. Said differently, if the center stars

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are in focus, the corner stars are distorted, and if the corner stars are in focus (not distorted), the center stars are slightly out of focus. Most stars in the image are within 75 microns (or 5 percent in size) of perfect focus.

The red arrows point to minimum FWHM values, which are interpreted to be best focus. The yellow FWHM value set on the chart was shifted slightly with a multiplier to separate the data sets for clarity. The center star did saturate and saturation could affect the FWHM and cause broadening of the focus zone.

Figure-13 Chart Interpretation The CFZ is still curved – even with a flattener. This is a reality of modern astrophotography. A remnant curvature after flattening is usually caused by a poor flattener design or a flattener being used outside of specs, or both. In this test, the incomplete field flattening is caused by a flattener that is out of range for the 650 mm lens. It means that the “CFZ” will go to zero as the distance from beam centerline increases on the sensor surface. Focus in wide-field astrophotography with a nonflattened or semi-flattened field becomes a

UNDERSTANDING THE CRITICAL-FOCUS ZONE OF A FAST APOCHROMATIC LENS

Figure 11

Figure 12

compromise for the photographer where the photographer must pick a focus point for best overall focus. In a mathematical sense, the CFZ depth for of a typical, nonflattened or semi-flattened fast apochromatic lens depends on both the f-speed of the lens and the distance from the beam centerline.

The Compromise!

Figure 14 is an updated photo using the 52-mm separation between the flattener/reducer’s flange and the plane of the Canon 20D’s sensor. This is a full-frame image with minimum development.

Figure 15 shows the 580 x 440 pixel upper right corner of full frame image in

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UNDERSTANDING THE CRITICAL-FOCUS ZONE OF A FAST APOCHROMATIC LENS This image is a composite of four, 2minute exposures at ISO 800, registered in DeepSkyStacker and added in Photoshop, and is full-frame. Please understand that creation of a contest-winning view of the Horsehead was not intended. It is, instead, an example of what can be quickly accomplished at the best focus possible with the optics tested.

The APM/TS Optics Flattener I have recently taken a series of photos using the TS Optics flattener available through APM and others – the flattener recommended by APM for the105/650 scope – and the early results are excellent. The CFZ seems to be quite a bit deeper than was obtained using the non-APM 0.85x flattener/reducer. I had no problem finding a focal point with all stars in focus – center or corner. But remember that the TS Optics lens does not reduce the focal length or increase the f-speed. Meanwhile, I cannot stress enough that I have, throughout these tests, found the APM scope to be of supreme quality, both optically and mechanically. There is simply no false color and the collimation is the best I have ever seen. It is truly collimated to the critical tolerances required for photography, when many mid-range scopes are simply collimated to accuracies more appropriate for viewing.

Figure 13

Figure 14

at 100 percent. This is the same area and magnification as shown in the earlier examples of focus such as Figure 5. This focus is excellent! This is a color image, so please notice the lack of false color, even in the extreme corner. The LZOS triplet lenses are amazing!

It is also important to say that the new 52-mm spacing may not be perfect.

I do not know if 51 mm or even 50 mm

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would work better, and would need to have a professional machinist take 1 or 2 mm off the adapter to see if the CFZ continues to improve.

Finally – A Real Astrophoto And for those of you who would like to see an example of this focus in a real astrophoto, Figure 16 provides a very-quick image of the Horsehead region of Orion.

GoldFocus 2.0 I also used the GoldFocus mask and analysis-software system for this last test to find initial focus settings. The GoldFocus process is much easier and faster than any other method I have used to date and I am extremely impressed with it. One advantage of the system is that it will tell you (by voice) which way to move the focuser and by how much! It has become a standard tool in my focus studies and astrophotography, and the results I achieve using it appear to be equivalent to the most detailed of my previous focus

UNDERSTANDING THE CRITICAL-FOCUS ZONE OF A FAST APOCHROMATIC LENS processes – especially when combined with the Rigel Systems stepper-motor focus system.

Summary Focus of a modern highquality, fast apochromatic lens is a precision process. It requires precision tools such as the Rigel Systems stepper-motor focus system and a focus interpreter such as the GoldFocus system.

But, the photographic results are amazing and well worth the effort and modest investment in these tools. I have never seen such pinpoint stars as I have gotten with the APM 105/650 LZOS scope and an appropriate flattener.

From this article, I am hoping to encourage the development of an auto-focus system that will produce a true 2-D and 3-D CFZ visualization.

This process would use medical CT-data-slice methods such as I produced manually for this article. This would not be a simple single-plane field-curvature drawing based on a single image, but would turn the stepper-motor focuser and imaging sensor into a CT scanner for a few minutes. The program would take 20 or 30 images to produce 3-D CFZ views and would then place the imaging sensor for optimum focus. The result would be a display that would be a perspective view of the CFZ with the imaging sensor placed precisely in the CFZ. My study of the CFZ and flatteners is ongoing and I will post new developments from these test series, as they happen, on my astro website at: www.steveluce.com/astro.

Figure 15

Figure 16

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Lunt Solar System LS152 Modular Design, Ease of Use and Cutting Edge Technology

By Stephen W. Ramsden and Brian Stephens

The last decade has seen an amazing upsurge in the amateur solar astronomy market. David Lunt’s revolutionary design work at Coronado set the stage for the industry to go from the realm of the university scientist to that of the average consumer. David’s son, Andy Lunt, has taken the hobby to extremes of technology and styling that his father could never have imagined and made it even more available to the amateur around the world. Lunt Solar Systems seems to add something new almost monthly to their extensive lineup of available solar telescopes and filters.

The LS152THa/CaK/Solar wedge setup is an extraordinary all in one solution to the amateur appetite for high resolution narrowband solar viewing and

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imaging.

The LS152 system is basically an f/6, 900-mm focal length, 152-mm achromatic refractor designed to allow for the use of all three popular types of amateur astronomy. It has a modular design which allows for the insertion of either a H-alpha module using an internal single etalon (<.7A) or double-stacked (<.5A) internal etalons, a choice of three sizes of Calcium K line (393nm) filters with removable energy-rejection filter, or a 2-inch white light Lunt solar Wedge. The scope can even be used as a high-quality night sky observing instrument by replacing the solar wedge with a standard diagonal. This scope could very well be the only thing you need to enjoy solar or conventional night astronomy in one package!

Hydrogen Alpha Using the LS152 in the Hydrogen Alpha mode is as easy as 1,2,3. The scope is housed in a sturdy golf-bag style hardshell case or aluminum sided hard-shell case which will hold all the modules as well as a couple of eyepieces.

Simply insert the red H-alpha module into the rear of the refractor and put in a Lunt Zoom eyepiece and you are ready to go. The views are breathtaking through this instrument in either the single- or double-etalon modes. There is a thin line of reddish gray spicules on the edge of the H-alpha Sun which took my breath away upon my first use of this scope. I had never seen them visually before in any of my other H-alpha big guns. The ample aperture of this

LUNT SOLAR SYSTEM LS152 system allowed these spicules to jump out at me the very first time I looked.

The included pressure-tuned etalon is a remarkable leap forward in solar scope technology. With this system the etalon never moves, tilts, or flexes, causing the dreaded sweet spot in so many competitors. The entire etalon is housed in an airtight barometric chamber and uses changes in air pressure (+/- 3 p.s.i.) to change the refractive index of the air between the etalon surfaces. The control for the pressure tuning is a motorcycle throttle style grip that equals its functionality with a smooth and innovative styling. The precise tuning and even illumination produced by this Doppler true tuning design is an exclusive feature on the Lunt Solar Systems scopes.

The H-alpha module is equipped with a 2-inch top-of-the-line Feather Touch focuser. You can insert any of the available H-alpha blocking filters (6-mmâ&#x20AC;&#x201C;34-mm) into this focuser and

Image 1 - Lunt LS152 pictured above (right) with Coronado 90 mm DS and Explore Scientific 127 mm in background for size comparison.

have plenty of in focus and back focus.

I am able to focus any of my cameras, binoviewers or eyepieces easily with room to spare using this innovative design.

Calcium K Now the fun part! To switch to either the CaK or Solar Wedge mode, simply loosen the three thumbscrews at the rear of the refractor and the entire

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LUNT SOLAR SYSTEM LS152 into the scope and tighten the three thumbscrews. Just like that you have transformed your top-of-the-line Halpha scope into a large aperture Calcium K scope on the fly without ever removing it from the mount…simply amazing if you ask me.

Image 2 - LS152 shown in H-alpha mode with B1800 blocking filter on CGEM mount.

H-alpha assembly slides out easily, allowing for insertion of the Calcium K/Solar Wedge module. The CaK module comes with its own stock Crayford 10:1 focuser and also has an available

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Feather Touch focuser. Just like with the H-alpha mode, you choose the size CaK filter that you want to use (12 mm–34 mm) and simply insert it into the module. Then you slide the entire module

White-Light Solar Wedge So, if that wasn’t enough Andy and Brian over at Lunt Solar Systems decided to make it a white-light/Solar Wedge scope as well. Remove the CaK diagonal from the focuser and insert the 2-inch Lunt Solar Wedge into it and you now have a fantastic highresolution setup for viewing white-light features like sunspots, faculae, and granulation. Remember, we still haven’t removed the scope from the mount or torn down anything to set up a different scope. This is all using the same base refractor!

One more thing…simply remove the wedge from the focuser and insert a stan-

LUNT SOLAR SYSTEM LS152 dard diagonal and you know have very respectable f/6 night sky refractor.

Thought I’d throw that in there just in case you were wondering.

Another neat feature of this wellthought-out design is that there is no need to ever try and find the Sun by looking directly at it. The solar finder required on so many other offerings in this market is unnecessary on this scope as it has, as a result of its incredible design, a built-in solar finder right on the mounting rings. All you have to do is look in the reverse direction down the tube and wait until the forward rings shadow is aligned with the aft rings surface and you have a perfectly aligned solar scope without any need for adjusting the finder…ever.

I have been using the LS152 extensively in my imaging and outreach for close to a year now and I can tell you it is a marvel to see and use. It is a monstrous scope when compared to my others and always gets all the ooohs and ahhhs from participants.

When the scope is torn down and packed up it fits neatly into either case and is only moderately heavy and very easy to transport with the included wheels on the golf-cart-style case. If you have carried around big Schmidts for years like me, this one is as light as a feather in comparison.

Thank you for reading and I certainly hope that all of you get a chance to look through this marvelous scope!

Image 3 - LS152mm scope in the with the CaK/white light module inserted.

Image 4 – Set up as a white light/Solar Wedge scope.

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ASTRO TIPS tips, tricks and novel solutions

DIY Desiccant Caps

By Joe Campbell For me, the changing of seasons means storing astro gear in an unheated garage and I’m always concerned about humidity and condensation buildup inside my telescopes. Since whatever type of end plugs they may have come with have long since been lost afield, I typically cap the openings with old 35-mm film canisters to prevent dust for entering the tubes. However, as I was preparing to store my scopes last year, I noticed a number of silica-gel packs on my work bench left over from the packaging of some blinds I had installed for my wife.

She refers to me as a pack rat for collecting such things. “Why anyone would save something that says ‘throw away’ is beyond me?” But sometimes being a bit of a frugal re-user comes in handy. As I looked at the packets and the film tube in my hand, the proverbial light bulb went off: “Why not drill a few holes in the end and stick some of these silica packets in there?”

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.

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Please send your information to tips@astronomytechnologytoday.com

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Six holes later, with silica packs nestled inside the perforated black canister, into the scope it went and all was generally good.

But, the canister wasn’t a perfect fit; there wasn’t enough of pressure between the focuser and cap to properly seal the OTA. So, consulting my work bench again, I selected an O-ring, slipped it around the former film canister, and rolled it back toward the cap to form a stop. When reinserted into the focuser the assembly provided a much better seal.

With the prototype complete, I considered the finer points of the design.

The 1/16-inch drill bit I originally selected wasn’t inspired by studied logic – it was just the size closest at hand – and the three-by-three matrix comprising nine holes was also just another best guess.

You could instead drill a circular pattern if you wanted to invest the effort. Also, while I use 2- to 1.25-inch adapters with all of my scopes, I asked myself, “What if I didn’t?” So I set about the house on a hunt to find sources of cheap 2-inch bottles. Of course, my wife was understandably puzzled as I systematically measured every bottle in the house, but after twenty-plus years she should be used to such.

The good news was some of the larger prescription bottles fit the bill as well as a many of the smaller vitamin containers.

The prescription bottles even had collars to roll the O-Ring against as a stop and in the case of the vitamin containers, which didn’t “lip,” one could simply glue the back side of an O-Ring in place, creating a make-shift stop.

Some final notes: If the silica-gel packs are left exposed when stored, they will simply absorb moisture from the surrounding air and become ineffective. I seal them in a zip-lock snack bag after squeezing out as much air as possible.

Also, as clearly marked on the packets, there is an ingestion risk, so the packs should be stowed up and away from children and pets. And as always, please wear safety glasses when drilling anything. Sight is one of our most precious gifts – especially when it comes to this hobby.

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