ASTRONOMY
TECHNOLOGY TODAY Your Complete Guide to Astronomical Equipment
UNIHEDRON SKY QUALITY METER-L • GOLDFOCUS FOCUSING SYSTEM • TECHNIQUE FOR FLAT FIELD IMAGES DENKMEIER OPTICAL SPECTRUM 60 PST UPGRADE • POWERING A DSLR • EXPLORE SCIENTIFIC 127 ED
A “Seismic Shift” for the Cassegrain Telescope Volume 4 • Issue 2 March/April 2010 $5.00 US
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Contents Cover Story: Pages 35 - 43 In 1976, we were celebrating our country’s 200th anniversary, and for tech geeks like the editor of this magazine, we were watching the 6 Million Dollar Man (loved the running sound effects) and, maybe even more important to a young man, watching the first year of Charlie’s Angels! Why do we bring this up? Well, it’s to put our readers in the proper frame of mind when we tell you that the design of the Starizona’s New Hyperion Telescope shown on the cover was inspired by a little known telescope design proposed in a paper in 1976. And we know it had to be in print, because there was no Internet then! We hope you enjoy learning more as you read Scott Tucker’s narrative of the inspiration and the vision for the scope. And we hope you enjoy the cover image of the Whirlpool Galaxy captured with the Hyperion and a SBIG STL-11000M. It is an LRGB image with exposure times of 480:240:240:240 minutes and was imaged by Chris Johnson.
In This Issue 12 Editor’s Note It’s Really About the People By Gary Parkerson 33 Designing the Hyperion Telescope A “Seismic Shift” for the Cassegrain Telescope By Scott Tucker 41 Explore Scientific 127 ED An Extremely Well Thought Out Package at An Attractive Price! By Craig Stark
15 OUT OF THIS WORLD - WONDERS OF THE SOLAR SYSTEM Offers World’s Largest Moon Sculpture
16 KNIGHTWARE Releases Deep-Sky Planner 5 17 ASTRONOMY TECHNOLOGY TODAY Announces Free Online Magazine Subscriptions for K-12 and College Students
55 GoldFocus Focusing System A New Approach to Achieving Critical Focus By Dave Snay
18 INTERNATIONAL ASTRONOMICAL SEARCH COLLABORATION Encourages Students to Participate in Asteroid Search Campaigns
61 A Technique for Creating Excellent Flat-Field Images Combining the Best Properties of Twilight Flats and Dome Flats Into a Single Technique By Rich Williams 67 Powering a DSLR Use the Same 12-Volt Source that is Probably Powering Your Telescope and Other Equipment By Rick Saunders
19 MWAIC AND MAW CONFERENCES AstroPhoto Insight Magazine
70 Unihedron Sky Quality Meter-L How Dark is Your Sky? By Erik Wilcox
49 Denkmeier Optical Goes Solar Spectrum 60 PST Upgrade By Russ Lederman
Industry News
72 Astro Tips, Tricks, & Novel Solutions Drive Your LightBridge or Other Dob With a SkyScout By Robert Stelmock
20 QSI New Software Updates
21 MILKYWAY@HOME Over 45,000 People Participating in Project
Astronomy TECHNOLOGY TODAY
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Contributing Writers
Contents New Products
Russ Lederman founded Denkmeier Optical, Inc. in 2001. He is the inventor of the Power
Switch and OCS System for binoviewers, the Power Switch Star Diagonal, and also co-developer of BIPH, a telescopic bi-ocular night vision device sold through nightvisonastronomy.com. He is an avid amateur astronomer with 30 years observing experience and uses a 20-inch f/5 Dob for night-time observing, and a PST with Spectrum 60 Upgrade for Solar observing.
22 CATSEYE COLLIMATION New HotSpot Primary Mirror Center Spot
Rick Saunders is an amateur astronomer, inveterate tinkerer and member of the Royal Astronomical Society of Canada, London Centre. His passion is DSLR imaging and on cloudy nights he spends his time designing and building equipment to help further that passion.
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.
Robert Stelmock has the astro bug, as he likes to say. He is retired and after joining his local club, Museum Astronomical Resource Society (MARS) in Tampa, Florida, he spends his time tinkering with telescopes and astrophotography.
Scott Tucker grew up in Michigan where one rare night the clouds finally parted and unveiled the stars. He works at Starizona where he writes educational guides for the Web, helps develop new products, shares his expertise on imaging and love of the night sky with the public, and even finds time to draw astronomical cartoons.
Rich Williams has a varied technical background with stints at Raytheon, Wang Laboratories, Boeing and Microsoft as well as being co-founder of Optical Mechanics, Inc. He has a lifelong passion for astronomy and his creation of the Sierra Stars Observatory Network is the culmination of his efforts to create a world class observatory that anyone can use.
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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23 ATIK USA Introduces 383L+ and 320E CCD Cameras, EFW 2 Filter Wheel, Off Axis Guider 24 ASTRO PHYSICS Introduces New Polar Scope 25 GARRETT OPTICAL Offers 100-mm F/6.1 Binocular Telescope 26 CELESTRON NexStar 90SLT and 127 SLT Maksutov-Cassegrain 27 ROYCE OPTICS To Soon Debut the “Ultimate Newtonian” 27 ADAM BLOCK New DVD - Powerful Processing in Photoshop 28 HOTECH Advanced CT Laser Collimator 29 ORION TELESCOPES AND BINOCULARS New BT100 Binocular Telescope 30 GERD NEUMANN JR. ASTRONOMY New Ronchi Eyepiece
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Tele Vue Optics www.televue.com page 8, 73 Teeter’s Telescopes www.teeterstelescopes.com page 51 Unihedron www.unihedron.com page 43 Van Slyke Instruments www.observatory.org page 31, 36 William Optics www.williamoptics.com page 2 Wood Wonders www.wood-wonders.com page 52 Woodland Hills Telescopes www.telescopes.net page 20
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ASTRONOMY
TECHNOLOGY TODAY
Volume 4 • Issue 2 March - April 2010 Publisher Stuart Parkerson
Editor’s
Note
Managing Editor Gary Parkerson
Associate Editors Russ Besancon
Gary Parkerson, Managing Editor
Karol Birchfield Jessica Parkerson
Art Director Lance Palmer
Staff Photographer Jim Osborne
Web Master Richard Harris
3825 Gilbert Drive Shreveport, Louisiana 71104 info@astronomytechnologytoday.com www.astronomytechnologytoday.com Astronomy Technology Today is published 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. The publication welcomes and encourages contributions; however is not responsible for the return of manuscripts and photographs. The publication, at the sole discretion of the publisher, reserves the right to accept or reject any advertising or contributions. For more information contact the publisher at Astronomy Technology Today, 3825 Gilbert Drive, Shreveport, Louisiana 71104, or e-mail at info@astronomytechnologytoday.com.
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Astronomy TECHNOLOGY TODAY
IT’S REALLY ABOUT THE PEOPLE We recently received a particularly poignant subscriber letter. A disabled veteran age 70, whose wife is also disabled, wrote to thank the ATT team for publishing the magazine, and to apologize that he would no longer be able to support it through his subscription due to the financial strains of declining health. While we receive many email messages and letters from subscribers who write to tell us how much they enjoy the magazine, this letter was different. That someone who was enduring such difficult times would make the effort to write to apologize for not renewing a subscription was singular. As many of you know, our publisher, Stuart, and I are brothers. Our stepfather, who is now in his 80s, is a veteran of three wars, and while he has our respect, admiration and gratitude for that service, we owe him much more for the steadfast care he provides our mother, who in recent years has experienced a decline in health. Our stepfather is unusually healthy and looks far younger than his age warrants, and I believe this to be just one benefit of his daily attention to our mom's well being, and to his focus on family. I say this because we realize how fortunate we are as a family. We realize also how very fortunate we are to have the support of ATT's subscribers and advertisers, without whom this magazine could not succeed. In recognition of this good fortune, and although it’s a small gesture in
the overall scheme of things, we will begin offering complimentary subscriptions to those who, for whatever reason, cannot afford to subscribe. The process is simple. If you are aware of someone who would enjoy the magazine, but cannot currently spare the price of a subscription, simply send us an email providing their name and address, and they will receive the magazine. There is no criteria or need for explanation of circumstances – just your recommendation. Please direct your requests to subscribe@astronomytechnologytoday.com. We will also honor your requests for confidentiality and will not burden recipients with explanation for such complimentary subscriptions. It's no secret that amateur astronomers tend to be on the grayer side, as my own graying (and receded) hair proves! Over the years we have had numerous discussions of how to better introduce new generations of enthusiasts to astronomy and many organizations currently sponsor successful efforts to do so. The ATT team would like to build on these efforts by introducing a program designed to make this magazine more easily available to students interested in astronomy. We are aware that a significant number of educators subscribe to the magazine, ranging from K-12 teachers to university astronomers. Beginning this March, ATT will offer all such educators the opportunity to provide free online subscriptions to
their students. For more details, please see the related item in the Industry News section of this issue. Finally, among the highlights of our ATT experience has been the privilege of working directly with leading astro-gear pros throughout the world who have been gracious enough to lend their insight and expertise to this magazine. One of the original, core goals of the ATT format was to provide readers a behind-the-scenes view to why and how industry professionals develop their products and to supply detailed technical information on these products “directly from the horse’s mouth,” so to speak. With the 2010 edition of the Northeast Astronomy Forum (NEAF) just around the corner in April and the Pacific Astronomy and Telescope Show (PATS) later in September, we thought it particularly appropriate in this issue to share articles contributed directly by more than one industry professional. We enjoy such articles not only for the technical insights they provide, but also because they permit us to better know the actual people behind the innovations that enhance our astronomy experiences. We trust these articles will allow you to experience what is demonstrated to us every day: that it’s not just a business to them, it's a passion! And we strongly encourage you to attend one of these remarkable astronomy forums, if not both. Each provides a unique opportunity to meet today’s leading astronomy technology innovators in person. Imagine a computer show with Bill Gates, Steve Jobs, and all of their peers, demonstrating their products and anxious to meet directly with you, talk shop, answer questions, and discuss future innovations. That’s exactly the experience these events offer to astronomy enthusiasts...well, that plus the irresistible lure of having every imaginable new astro product right at their fingertips! If you do attend, please look me up as well, although I'm not likely to actually be in the ATT booth. Like you, I'll be visiting every other exhibit, gawking at all the new stuff, meeting new friends, and visiting old ones. I hope to see you there.
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INDUSTRYNEWS
OUT OF THIS WORLD - WONDERS OF THE SOLAR SYSTEM Offers Worlds Largest Moon Sculpture Ok, we know that this is a little off topic for our typical industry news item, however we sometimes forget that we have subscribers who live all over the world, not just in North America. We received an email about this exhibit from one of our subscribers in Germany and just thought it was really amazing. The information here is from a press release that was forwarded to us, and the website for more information is in German, which unfortunately, no-one who works with our magazine can read. If one of our readers actually gets to see the exhibit, we’d like to hear about it! The inside of a 380-foot tall obsolete gas holder, the Gasometer in Oberhausen, is the space for a new exhibit called “Out Of This World Wonders of The Solar System.” It includes the largest moon sculpture in the
world - an 82-foot wide replica of the moon hanging in a cathedral-like space under the holder’s 328-foot roof, as well as replicas of the sun and its planets in a space 223 feet wide. The exhibit explores scientific, cultural and artistic perspectives on the creation of our solar system in the vast dimensions of the cosmos. The true-to-scale moon sculpture is based on high-resolution satellite images of the moon and is shown, as are all other stars and planets, in elaborate detail along with its various phases and light phenomena. The vastness of the exhibit venue echoes the vastness of outer space, and ethereal music adds to the exhibit experience. The exhibit, open through December 30, 2010, is one project of “Ruhr 2010, the European Capital of Culture” – a year-
long series of art events and exhibits in Germany’s Rhine Ruhr area, a metropolitan region with a dense concentration of cities and a population of 11.5 million, with Düsseldorf and Düsseldorf International Airport at its center. Direct flights to Düsseldorf International Airport (DUS) from the US are available from Atlanta, Chicago, Ft. Myers, Los Angeles, Miami, New York (JFK and Newark), and San Francisco. Oberhausen and the Gasometer are about 20 minutes by train and car from Düsseldorf, and trains are available from train stations at DUS and Düsseldorf city center. (We included this information for our readers in the US who might want to travel to the exhibit!) To find more exhibit information about the exhibit and the Gasometer visit www.ruhr2010.de.
Astronomy TECHNOLOGY TODAY
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INDUSTRYNEWS
KNIGHTWARE Releases Deep-Sky Planner 5 Knightware has announced its release of Deep-Sky Planner 5, a Windows-based software program that allows visual and imaging observers to plan and log their observations. Additional data and a wide feature set are combined with ease of use, standards compliance, and open data exchange in this latest release of the product. The product operates on Windows 7, Vista and XP. The Deep-Sky Planner 5 database places updated and expanded data for over one million objects at users’ fingertips. Reports of the data can be customized extensively in content and appearance. Smart inter-operation with supported planetarium programs allows users to select a celestial object in a report and switch instantly to a planetarium view of the object scaled to a field of view defined by the user, the current optical system or the object being observed. Several commercial and free programs are supported, including TheSky6, Starry Night, Redshift and Cartes du Ciel. The fully integrated observing log allows storage and report-
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Astronomy TECHNOLOGY TODAY
ing of typical observation data, extensive sky and weather conditions data, support for reading Unihedron’s Sky Quality Meter and convenient access to customizable online resources. Users can attach an image to an observation; exposure data from a JPEG or FITS image can be viewed and appended to the observation with a click. Ease of use and standards compliance are demonstrated by the Windows compliant user interface and compatibility with the Windows 7 and Vista User Account Control security scheme. This attention to detail means fewer security problems and a smaller learning curve when using the software.
Open data exchange characterizes both reporting and observing log data. Reports can be saved for use in other software in plain text, HTML or delimited text (CSV) formats. Users can import and export observations in the non-proprietary Open AstronomyLog 2.0 format used by other commercial and free products, or the native Deep-Sky Planner format. Deep-Sky Planner 5 includes thorough documentation, online product support and online product updates. An online product community allows licensed users to exchange resources used by the product. For full product description please see www.knightware.biz.
INDUSTRYNEWS
ASTRONOMY TECHNOLOGY TODAY Announces Free Online Magazine Subscriptions for K-12 and College Students As was mentioned in this issue's Editor's Note, we here at ATT have often pondered how we could better help introduce more young people to astronomy. This is a pertinent concern given that the average age of astronomy enthusiasts appears to be increasing. Educators often write to share their ideas and insights and to ask for our assistance in helping their students to more easily participate in practical astronomy. One recent suggestion was that we provide direct student access to the magazine. We talked it over and feel that this was a great idea! And so, we are pleased to announce a new program designed to make ATT available at no charge to any desiring student. This program will allow science educators (not just those involved in astronomy) to provide direct online access to their students. Better yet, because this access will be via the ATT website, we can offer the program worldwide.
We mention this because as we were designing this program, one of the educators we visited with was Dr. J. Patrick Miller of Hardin-Simmons University. Dr. Miller is the founder of the International Astronomical Search Collaboration (please see the related news item in this issue) and is working directly with students across the globe. We sought his input and advice with a view toward a U.S. based program and he thought it "sounds like a great idea," but wanted to make sure international students could participate as well. Signing up for the program is simple: educators need only email us at subscribe@astronomytechnologytoday.com and we will respond with all information
needed to enroll their students. Students will be provided with access to the online version of the magazine and can view each new issue as often as they want. And because all issues of ATT are available online, they can access all issues from our first forward. We encourage all readers to share this information with any science instructor they think might be interested in participating and also encourage interested students to contact us directly. If you are a member of an astronomy club or other astronomy organization, please feel free to announce this program in its newsletter or on its website. For more information, please visit www.astronomytechnologytoday.com.
Astronomy TECHNOLOGY TODAY
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INDUSTRYNEWS
INTERNATIONAL ASTRONOMICAL SEARCH COLLABORATION Encourages Students to Participate in Asteroid Search Campaigns The International Astronomical Search Collaboration (IASC) is an educational outreach astronomy program for high schools and colleges, provided at no cost to the participating schools. IASC (pronounced “Isaac”) runs 12 asteroid search campaigns per year, each lasting 45 days with 15 schools. The campaigns are run two at a time, one from a 24inch telescope and another from a 32-inch telescope, both located at the Astronomical Research Institute Observatory in Illinois. IASC is a collaboration of HardinSimmons University (Abilene, TX), Lawrence Hall of Science (University of California, Berkeley), Astronomical Research Institute (Westfield, IL), Global Hands-On Universe Association (Lisbon, Portugal), Sierra Stars Observatory Network (Markleeville, CA), Tarleton State University (Stephenville, TX), NASA Wide-Field Infrared Survey Explorer (Space Sciences Laboratory), and Astrometrica (Austria). Currently there are two campaigns in progress. The International Asteroid Search Campaign has 15 schools from 9 countries on 4 continents and the countries include Bulgaria, China, India, Morocco, Panama, Poland, and United States. The NASA-WISE Asteroid Search Campaign has 15 U.S. schools, and is part of the WISE educational and public outreach program for the Widefield Infrared Survey Explorer mission launched in December 2009. Rich Williams, of the Sierra Stars
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Astronomy TECHNOLOGY TODAY
Observatory Network, is closely involved with the project. “IASC runs campaigns for countries around the world,” says Williams. “Students work closely with the mentors to learn astrometry techniques and they have discovered dozens of main-belt asteroids while also doing important follow up work on NEOs. The excitement of discovery along with contributing to the scientific community is very rewarding and compelling for the students. I believe that it is an excellent model for fostering interest in astronomy science that can have a profound effect in the student’s personal development.” Dr. J. Patrick Miller is the IASC Director and founder of the program. He is a professor of mathematics at Hardin-Simmons University and also teaches introductory astronomy and astronomical research methods at the university. For the International Asteroid Search Campaign, discovery images come from the prime telescopes at the Astronomical Research Institute Observatory and follow-up images come from the Sierra Stars Observatory Network. Additional follow-up images come from the Tarleton State University Observatory. The Minor Planet Center at Harvard, the official body that deals with astrometric observations, and orbits of minor planets, asteroids, and comets, requires that follow-up images be taken within 7 days of any MBA discoveries by students and close coordination is important. If the follow-ups are missed due to weather or
telescope maintenance, the discoveries are lost and the process has to start over again. When students make a discovery, three IASC volunteers in Bulgaria, Russia, and Italy work behind the scenes to review the discovery and organize the follow-up images. After the follow-ups are completed, the discovery report and follow-up report are then sent to the Minor Planet Center. During a 45-day campaign period, students usually discovery 15 Main Belt asteroids. Since the start of IASC in October 2006, students have discovered over 200 MBAs. In addition they have made more than 1,000 NEO observations, 200 NEO confirmations, and 100 virtual impactor observations. In February 2010 alone, five original discoveries of asteroids were found in the Main Belt located between the orbits of Mars and Jupiter. These discoveries were made by high school students in Texas and in New Hampshire, and from college students in Texas and Poland. Also in February two observations were made of near-Earth objects that are shown to have orbits that pose a potential impact hazard with Earth. These observations were made by high school students in Bulgaria and Wisconsin. And over 30 follow-up observations of known near-Earth objects were made in February, allowing further refinements to their orbit calculations. More information can be found at http://iasc.hsutx.edu.
INDUSTRYNEWS
MWAIC AND MAW CONFERENCES AstroPhoto Insight Magazine The fourth annual Midwest AstroImaging Conference (MWAIC) and the second Mac Astronomy Workshop (MAW) will be taking place just outside of Chicago at the Northern Illinois University Outreach Center in Hoffman Estates on July 23-24, 2010. The combined conference is hosted by Al Degutis, Editor-in-Chief of AstroPhoto Insight Magazine, and will feature experts on the latest in Windows and Mac astronomy and astro-imaging software, as well as platform independent image processing techniques. An optional pre-conference, one-day image processing workshop conducted by renowned imager Adam Block, will take place on Thursday, July 22, 2010. Adam will provide a complete imaging workflow and show attendees how to address common image challenges. The two-day conference will feature a keynote address by Dave Jurasevich of Mount Wilson Observatory and many expert speakers covering a wide range of software and techniques. Alan Friedman will provide his planetary imaging workflow expertise using Astro IIDC, Image Stacker and Photoshop. Ken Crawford will share his 6 filter narrowband imaging technique and Paul Rodman will show attendees how to utilize AstroPlanner, while Darryl Robertson will shed some insight on Equinox. Neil Fleming will cover the newly released version of CCDStack. Mike Unsold, developer of ImagesPlus, will provide insight on how to leverage this power application to produce great images. PixInsight users, or those interested in getting started with it, will learn its unique interface from Sander Pool who has authored numerous tutorials on the software.
Imagers interested in learning how to use Stark Lab’s Nebulosity will enjoy meeting the software’s developer and daytime brain scan analyzer, Craig Stark, who will provide tips on getting the most out of the software program. If you are confused by the many autoguiding options, Bob Piatek’s ‘Top 10 Ways to Guide’ presentation will help guide attendees in their endeavors. Alan Erickson, Senior Software Engineer at Adobe, will return for the third year and provide an inside look at Photoshop’s features that are relevant to astrophotographers. Adam Block will share many advanced Photoshop image processing techniques that help him produce APOD quality images. This is also a great time to meet with vendors and see their latest products. Exhibitors include Adobe Systems, DC3 Dreams, Quantum Scientific Instruments (QSI), Atik USA, Starlight Xpress, Optec Inc, ImagesPlus and the Mount Lemmon SkyCenter. In addition to the great presentations, workshops and vendor exhibits, the Midwest Astro-Imaging Conference and Mac Astronomy Workshop offers a luncheon that surpasses the box lunches at most imaging conferences, free wireless Internet throughout the facility and great door prizes. In previous years, some attendees and speakers have taken advantage of the location and time of year to extend their visit for some sightseeing in Chicago. For more information about the conference, and to take advantage of the early registration discount, visit www.mwaic.com and join the MWAIC Yahoo Group (http://groups.yahoo.com/ group/mwaic/) for up-to-the-minute updates.
Astronomy TECHNOLOGY TODAY
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INDUSTRYNEWS
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Astronomy TECHNOLOGY TODAY
Small subframes can now be read from anywhere on the sensor in approximately two seconds. This dramatically reduces the time required for focusing and makes focusing easier whether focusing manually or with an automated focusing routine. 4x4 binning allows low resolution images to be read in about six seconds. This higher binning mode makes it easier for quick shots to get the framing of the target just right. Also, a new release of software and drivers is now available for all QSI 500 Series cameras. Release 5.2 adds support for 64-bit systems under Windows XP, Vista and Windows 7. The new release also installs the latest low-level USB drivers, adds overscan control to the QSI camera updater applications, offers bug fixes for retaining filter offsets in the API, provides improved USB FTDI bus enumeration and device conflict detection, and includes QSI API for Linux, release 5.2.1. For more information or for download options please visit www.qsimaging.com.
INDUSTRYNEWS
MILKYWAY@HOME Over 45,000 People Participating in Project The ways people can become involved in astronomy have become more diverse than ever. They can actively use astro equipment, purchase time on telescopes remotely accessible via the Internet for imaging and research, or just learn more about astronomy using their computer, iPhone, or one of our favorites, by reading a certain astronomy equipment magazine! Another way that over 45,000 people from more than 179 countries are participating in an astronomy project is the MilkyWay@Home project, to help solve the largest and most basic mysteries of our galaxy. Each user participating in the project signs up their computer and offers up a percentage of the machine’s operating power that are dedicated to calculations related to the project. This means that each personal computer is using data gathered about a very small section of the galaxy to map its shape, density, and movement. With donated access to decade-old desktops to new netbooks, computer scientists and astronomers at Rensselaer Polytechnic Institute are mapping the shape of the Milky Way galaxy. And amazingly, the combined computing power of the MilkyWay@Home project recently has surpassed one petaflop, a computing speed that surpasses the world’s second fastest supercomputer. The project, uses the Berkeley Open Infrastructure for Network Computing (BOINC) platform, which is widely known for the SETI@home project used to search for signs of extraterrestrial life. Today, MilkyWay@Home has outgrown even this famous project, in terms of speed, making it the fastest computing project on the BOINC platform and perhaps the second fastest public distributed computing program ever in operation.
The interdisciplinary team behind MilkyWay@Home, which ranges from professors to undergraduates, began the formal development under the BOINC platform in July 2006 and worked to build a volunteer base from the ground up to build its computational power. Each user participating in the project signs up their computer and offers up a percentage of the machine’s operating power that will be dedicated to calculations related to the project. For the MilkyWay@Home project, this means that each personal computer is using data gathered about a very small section of the galaxy to map its shape, density, and movement. In particular, computers donating
processing power to MilkyWay@Home are looking at how the different dwarf galaxies that make up the larger Milky Way galaxy have been moved and stretched following their merger with the larger galaxy millions of years ago. This is done by studying each dwarf ’s stellar stream. Their calculations are providing new details on the overall shape and density of dark matter in the Milky Way galaxy, which is widely unknown. The research project is funded primarily by the National Science Foundation (NSF) with donations of equipment by IBM, ATI, and NVIDIA. More information about this project and how you can join the effort can be found at http://MilkyWay.cs.rpi.edu/.
Astronomy TECHNOLOGY TODAY
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NEWPRODUCTS
CATSEYE COLLIMATION New HotSpot Primary Mirror Center Spot The Catseye Collimation system and precision products provide cutting-edge passive-tool collimation technology for the Newtonian observer. High-resolution, bright image queues and ease of use are the hallmarks of this uniquely engineered set of collimation tools for fast and easy alignment of scope optics day or night. Jim Fly of Catseye is always looking for ways to improve on an already good thing, and from a lively discussion with Catseye users on an astronomy forum the new HotSpot was born. The HotSpot is a primary mirror center spot and accompanying centerspot template. This new novel center-spot geometry combines the advantages of both the classic “donut” and Catseye triangle to provide more axial-error
resolution and correction capability when using the Catsye Blackcat or Telecat Cheshire functionality and Infinity XLK Autocollimator offsetpupil reflection alignment. We guess this proves that good things really do come in small packages. For more information visit www.catseyecollimation.com.
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Astronomy TECHNOLOGY TODAY
NEWPRODUCTS
ATIK USA
Image 1
Introduces 383L+ and 320E CCD Cameras, EFW 2 Filter Wheel, Off Axis Guider The new Atik 383L+ (Image 1) is an 8-megapixel camera using the Kodak KAF 8300 CCD. It offers a large number of pixels at affordable pricing which helps make this multimegapixel, cooled camera accessible to a growing group of astro imagers. Atik utilizes its 314 camera platform to support Kodak’s CCD which offers several advantages including very low read noise circuits and the reliability from of an established design. The Atik 383L+ features their most advanced cooling system to date. Atik utilizes the latest, high-efficiency Peltier modules, tiny temperature sensors located under the CCD and a centrifugal fan and heatsink. The fan is especially important as it allows a large volume of air to move over the heatsink while running the fan slowly, eliminating vibration to the camera that might blur an image. Shutters present a particular challenge in camera design. As moving mechanical parts they can be subject to some reliability issues. Up to this point all the Atik cameras have used interline CCDs that have electronic shutters. The new Atik 383L+ uses a full-frame CCD and utilizes a mechanical shutter for improved reliability. The camera is powered by a single 12V supply negating the need for multiple power packs in the field. The CCD chamber is kept moisture free by using extremely efficient molecular sieves as desiccant. These will last years in normal use, and when they need replacement it’s a simple job not requiring the camera to be opened. The camera has a standard Tthread connection on its front and can be used with Atik’s new Filter Wheel (Image 2) and Off Axis Guider unit
(Image 3). For focal ratios of f/5 and above standard 1.25-inch filters can be used without vignetting. Faster focal ratios will need flat field correction or larger filters (36-mm or 2-inch). The camera body and shutter will work down to f/2 without vignetting. The Atik 383L+ features 8.3 million 5.4µm square pixels for high resolution imaging, ultra low read noise for great sensitivity, is lightweight with no flexure of the telescope focuser tube, and offers a highly efficient set point cooling to 40 degrees max below ambient. The camera comes with Atik’s Capture image acquisition software as well as their Dawn image processing application which eliminates the need for third party software to take and process images from the camera. Plug ins are supplied for users who wish to use other software such as Maxim DL, Astro Art or CCD Soft. Another new offering from Atik is their 320E (Image 4) which is a 2 million pixel camera that offers the opportunity to take wide field images of the sky at high resolution utilizing a Sony ICX-274 CCD. As with the Atik 314E, its relatively small pixels make it ideally suited to the popular short focal length refractors. The sheer number of pixels allows very high resolution images to be taken which will look great on the web or printed out at A4 and greater sizes. Like its siblings the Atik 314E and Atik 314L+ it is based on the Atik 3 series platform which offers ultra low read noise for great sensitivity and high efficient cooling to 25 degrees below ambient. The platform features a USB 2.0 interface for fast readout, highly efficient cooling and low weight.
Image 2
Image 3
Image 4
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NEWPRODUCTS
ASTRO PHYSICS Introduces New Polar Scope The new Astro Physics Polar Scope will allow owners to quickly align their mount on the pole stars to ensure greater tracking accuracy throughout observing sessions. The reticle was designed for use
in both the Northern and Southern hemispheres. The reticle is marked for epochs 2005 through 2030 and has been improved for users in the southern hemisphere compared to the prior reticle for the last epoch. Even users of the Astro Physics GTO computerized mounts will find these polar scopes useful, particularly if the owner’s telescope is not orthogonal to the mount. The unit threads into the base of the polar axis of all past and present AP models of the 400, 600, 600E, 800, 900, 1200 and Mach1GTO German Equatorial heads (except the first black 1200
mounts that were produced). The illuminator, with red LED, allows users to see the reticle at night. All current and former Astro-Physics control boxes allow the user to adjust the brightness of the reticle either with a built-in rheostat, keypad firmware or PC software control. The LED cable allows owners to power the illuminator directly from the mount's control box. Included with the polar alignment scope are two covers, LED cable, and 0.9-mm hex wrench for reticle alignment. Also available is the AstroElectric Polar Scope Dimmer Controller, a battery-powered controller unit that powers the illuminator for the Polar Alignment Scope and allows for the adjustment of the LED brightness. It can be used when owners don’t wish to power their illuminator from the mount’s control box. It
can also be used to replace the battery pack that was included with the earlier Astro Physics Polar Scope versions which will eliminate the need to try to determine which polarity cable is needed. One of the jacks on the top of the controller has standard polarity; the other has reverse polarity. If the LED doesn’t light while plugged into one jack, simply use the other. For more information, visit www.astro-physics.com.
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Astronomy TECHNOLOGY TODAY
NEWPRODUCTS
GARRETT OPTICAL Offers 100-mm F/6.1 Binocular Telescope Essentially a scaled-up version of their 70-mm f/5.4 model, the Garrett 100-mm f/6.1 Binocular Telescope is designed with integrated 90 degree angled 1.25-inch helical focusers, which makes it a great choice for astronomy. It weighs in at just 14.3 pounds and will accept virtually all 1.25-inch telescope eyepieces and still be light enough for quick and easy setup. The precision helical focusers are angled at 90 degrees to make observing even at the zenith comfortable. The binocular offers the features of a rich-field telescope – such as the ability to easily vary magnification – with the three-dimensional viewing experience of a binocular. The flat-field objective lenses operate at an f/6.1 focal ratio, which is slow enough to deliver high-contrast views of deep space objects and solar system targets alike. The binocular includes a set of standard 1.25-inch oculars, 18.5-mm (63 degree AFOV) focal length, yielding 33x magnification and a true field of view of 1.9 degree. Additionally, users always have the ability to expand the magnification range by inserting virtually any 1.25-inch telescope eyepiece from 40-mm down to about 9-mm. All air-to-glass surfaces in the air-spaced achromatic objective lenses and the prisms are broadband multicoated and the precisely-polished prisms are crafted from high-index BaK4 optical glass. The cast-aluminum binocular body features a durable and attractive glossy white finish, integrated retractable dewshields and a matching removable carrying handle. One special feature built into the binocular telescope is the unique twistlock compression ring eyepiece holders this is essentially a scaled-down version of the system used on Garrett’s 150-mm binocular telescope, and it makes switching and properly centering eyepieces easy.
Garrett recommends two mounting solutions for the scope for purchasers that don’t already have a mount. For those looking for an affordable, conventional tripod, they recommend the Garrett Series 5000 which is available as a package with the scope. A more robust option is Garrett’s Helix 10-inch fork mount. The binocular telescope can also be use with many heavyduty tripods or parallelogram mounts with the standard 1/4inch 20 threaded mounting plate that’s integrated into the design.
Included with each binocular telescope is a high-quality aluminumtrimmed carrying case. Each scope is individually tested for collimation as part of Garret’s 14point inspection, and any necessary adjustments, including collimation, are performed by their technicians. It is covered by a two-year warranty and 30-day return policy. Garrett Optical’s 100mm f/6.1 Binocular Telescope is available for $1,099.95 US and can be packaged with the Garrett Series 5000 Tripod Plus Head for $200 US more. For more information visit www.garrettoptical.com.
Astronomy TECHNOLOGY TODAY
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NEWPRODUCTS
CELESTRON NexStar 90SLT and 127 SLT Maksutov-Cassegrain Designed to be an affordable entry level to mid-level computerized GoTo telescope, the NexStar line of SLT refractors, reflectors, and Maks are available in popular sizes and are loaded with design features. With preassembled, adjustable stainless steel tripods, and quick-release fork arms and tubes, NexStar SLT telescopes can be set up in a matter of minutes – with no tools required. The new NexStar 90SLT is a 90-mm Maksutov-Cassegrain and the new 127SLT is a 127-mm Maksutov-Cassegrain. Both scopes feature a fully computerized alt-azimuth mount, StarPointer finderscope, quick-release fork arm mount, optical tube and accessory tray, stainless steel tripod and accessory tray, and The Sky astronomy software. Powered by 8 AA batteries or an optional AC adapter these GoTo’s are easy to travel. The internal battery compartment
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Astronomy TECHNOLOGY TODAY
provides power to the high precision servo motors for rigid low-vibration performance while eliminating cord wrap issues associated with external battery packs. With the ergonomically designed hand control a touch of a button can select the object catalog, change the slew speed, view information about an object, or simply know if a desired object is visible in the sky. Both scopes also feature a computerized mount utilizing Celestron’s proven NexStar computer control technology, offering a database which allows the telescope to locate over 4,000 celestial objects. Also included is upgradable software, internal
battery compartment, auxiliary port for additional accessories, and NSOL telescope control software for basic control via computer. Using Celestron’s patented SkyAlign, simply input the date, time and location into the hand control then slew the telescope to any three bright celestial objects in the sky. Great for those new to astronomy, users don’t need to know the names of the stars – they can even pick the Moon or bright planets! Both scopes are affordably priced with the NexStar 90SLT at $419.95US and the 127SLT at $549.95US. For more information visit www.celestron.com.
NEWPRODUCTS
ROYCE OPTICS To Soon Debut the “Ultimate Newtonian” We've enjoyed visiting with Bob Royce over the years, discussing amateur astronomy in general and optics in particular – especially his developing plans for an "Ultimate Newtonian." We were also excited for Bob when we learned that his optics were used by Australian Anthony Wesley in the scope with which he discovered the now famous Jupiter impacts of July 2009. In fact, Bob was actually one of the first people Anthony notified of
the discovery. When we last spoke with Bob, he reported that his new Newtonian is currently in the prototype stage and will be in production soon. His general goal has been to create a scope of "superlative design that makes it second to none," an all aluminum scope designed to rival the performance of Apos. Each scope will be custom built by Bob and he promises that all will include nothing but the highest
grade components available, including his renowned Royce optics. While he has not released pricing for the new scopes, they will definitely create a new category of Newtonians and we anticipate quite a waiting list for these limited production scopes. Bob has promised ATT a first peak at the new scopes and we will publish a review at the earliest opportunity. Meanwhile, visit www.rfroyce.com for further developments.
lights the most common tools used to adjust and enhance images. Every relevant button, tab, and menu is described and subsequently used to process and improve pictures. Photoshop specific concepts of Layers, Masks, and Blending Modes are thoroughly explored and used. Each section shows concrete examples of significant “effects” that DVD owners can start using immediately on their own images. The DVD is in 24 sections which includes content on navigating and using
the tools within Photoshop and very specific astroimaging techniques including Star Replacement and Substitution, Stars and the Minimum Filter, Sky and Star Adjustments, Fixing Scattered Light, and much more. By the end of this instructional experience, owners will not only understand Photoshop more intuitively but also begin to synthesize the techniques shown and develop their own image processing solutions and enhancements. For more information visit www.caelumobservatory.com.
ADAM BLOCK New DVD - Powerful Processing in Photoshop Adam Block continues to share his expertise as one of the world’s premier astro imagers with his new DVD - Powerful Processing in Photoshop. This DVD on Photoshop is part of his continuing series of tutorials “Making Every Pixel Count”. This is a data DVD meant for display on a computer using a web browser (Macromedia Flash files) and will not play on a TV. The video is intended for Photoshop CS3 or later and PC and Macintosh users are supported. The new DVD not only introduces Photoshop to beginners but also demonstrates powerful processing techniques used by experienced astrophotographers. Featuring nine hours of video, the DVD begins with a tour of Photoshop that high-
Astronomy TECHNOLOGY TODAY
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NEWPRODUCTS
HOTECH Advanced CT Laser Collimator Star collimation is a great way to collimate but typically requires setting up a tracking mount and wait until dark to do it. HoTech’s Advanced CT Laser Collimator facilitates collimation of Cassegrain Telescopes. It uses multiple collimated lasers to simulate the flat-wavefront lights from a distant star and passes the lasers through the entire telescope’s optical system twice, then back to its target for a complete diagnostic and an accurate collimation reading of telescope optics. This collimation technique and technology keeps telescope focus at infinity during collimation. It does not require focusing near infinity to achieve high-accuracy collimation. The target is positioned within half of the telescope's focal length directly in front of the telescope during the entire collimation process. A simple one-person operation, users will be standing between
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Astronomy TECHNOLOGY TODAY
the telescope and the collimator adjusting the secondary mirror knob to bring the returning lasers on the same track. This instrument is precision machined from a solid aero-space grade aluminum plate, then hardened to keep the entire mounted laser system thermally stable achieving accurate collimation. The rigid, ultra thin profile, and light-weight design makes the unit portable and simple to setup and use. The Advanced CT Laser Collimator simulates a real distant star light path at a compact distance; therefore it can collimate most telescopes that use star collimation as their primary collimation method. For the standard model, the collimating telescope requires >7.5inch diameter primary mirror and <6.2-inch diameter secondary mirror. For more information visit www.hotechusa.com.
NEWPRODUCTS
ORION TELESCOPES AND BINOCULARS New BT100 Binocular Telescope Sometimes we forget that while Orion offers a myriad of astronomy products, they also offer numerous other products including general use binoculars, hence Orion Telescopes and Binoculars. So its more than appropriate that they have introduced the BT100 Binocular Telescope, with optical quality and features you’d expect of an Orion product. This premium binocular telescope features large 100-mm aperture objective lenses and fully multi-coated optics with BAK-4 prisms for gathering ultra-bright, high-contrast views of the night skies. The BT100s’ 90-degree viewing angle allows comfortable tripod-mounting (tripod not included) with quality details individual eyepiece focus. The included 25-mm Sirius Plossl eyepieces provide 24x magnification in the 609-mm focal length binocular telescope. The standard 1.25-inch eyepiece holders are compatible with most 1.25inch eyepiece pairs to provide different magnification levels. Included is a removable carry handle, two lens caps, and a custom foam-lined hard carry case with removable shoulder and strap, plus 2 lock latches with keys. The rugged body construction and waterproof design ensure the BT100’s will provide viewing enjoyment for years to come. When observing with large-aper-
ture binoculars like the Orion BT100s, a sturdy photo tripod or altazimuth mount is required (the weight and magnification of the binoculars make it impossible to hold them steady with your hands!). To attach the BT100 to an altazimuth mount that utilizes a dovetail holder, like the Orion VersaGo mount, an optional dovetail L-bracket (available as an option from Orion) is needed. The L-bracket connects to the BT100’s mounting plate, and has a
dovetail bar that goes directly into the mount’s dovetail holder. Another nice feature of the BT100 is the extendable lens shades. These increase image contrast by preventing glare (unwanted stray light) from entering the objective lenses of the binoculars. They also slow the formation of dew on the objective lens exteriors. For more information visit www.telescope.com.
Astronomy TECHNOLOGY TODAY
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NEWPRODUCTS
GERD NEUMANN JR. ASTRONOMY PRODUCTS New Ronchi Eyepiece Gerd Newman, Jr. of Astronomik has announced the introduction of a new Ronchi Eyepiece. The device consists of a main body made of black anodized aluminum with a 1.25-inch shaft. The eyepiece is equipped with vacuum metalized chrome on glass grating with 10 lines per millimeter. The grating is on the telescope side of the glass and is exactly in the same plane as the outer stop. Says Gerd, “This handy new accessory will provide useful assistance when checking the quality of nearly any telescope currently on
the market. Most common aberrations that might affect a particular optical design can be seen in a Star Test but this requires very steady air and an experienced observer to be reliable. Compared to the Star Test, the Ronchi Test works also with moderately unstable air and also a beginner will be able to do a very useful analysis of an instrument after only a small amount of practice.” The Ronchi Eyepiece is an eyepiece-like tool that allows the user of virtually any telescope to easily determine the quality of the optics with little or no
prior know-how. It is used like a normal 1.25-inch eyepiece and is inserted a telescope and then focused with the focuser. Users will see bars that depict the surface of the optics. The image shown here is a theoretical ronchigramm pattern of perfect telescope optics. When focused on a bright star, the parallel lines can be used to identify many of the common problems that can be experienced with telescope optics. The lines may be curved or distorted indicating a problem, or if they are relatively straight and parallel, this can indicate that the optics are performing properly. Some of the problems that can be observed are spherical overcorrection or undercorrection, turned down edge, central elevation or depression, zonal aberration, and others.
A user manual comes with the device and includes a table which shows the Ronchi images of all major optical aberrations. Often users will not see a single error but a combination of them. This might result in a more difficult interpretation, but as users gain experience they will be able to see the dominating error more easily. Gerd Neumann Jr.’s Ronchi Eyepiece is shipped in a protective housing with a short manual in English and German. For more information visit www.gerdneumann.net.
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Astronomy TECHNOLOGY TODAY
Designing the Hyperion Telescope A â&#x20AC;&#x153;Seismic Shiftâ&#x20AC;? for the Cassegrain Telescope By Scott Tucker
Starizona is known for innovative astronomical products, and it was only a matter of time before we took our cumulative experience and tried our hand at developing a complete telescope. As astrophotographers ourselves, it made sense to design a high-end imaging telescope. Imaging is the future of amateur astronomy, with more and more observers taking to photographing the night sky. There seemed to us to be a market for an astrograph for advanced imagers at a more affordable price point than what was currently available. Plus there was an opportunity to develop advanced features that no other telescopes had. Our foray into the world of astrophotography began with the HyperStar
system for Schmidt-Cassegrain telescopes. While the HyperStar design excels at wide-field imaging, we felt that there was something to contribute on the high-resolution-imaging front. At the time the Hyperion design was conceived, basically the only choice for high-end, high-resolution imaging was a Ritchey-ChrĂŠtien (RC) design. While these telescopes can be excellent performers, they have one main drawback: price. It seemed that
there might be similar designs out there that could be made for much less money. Existing Telescopes The Hyperion is a Cassegrain-type telescope. There are numerous telescopes that use the Cassegrain configuration, which has a concave primary mirror, convex secondary mirror, and focal plane behind the primary mirror. The most common are the Schmidt-Cassegrain telAstronomy TECHNOLOGY TODAY
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DESIGNING THE HYPERION TELESCOPE image, meaning accurate positional measurements can be made. But over a large field of view, the stars can still be distorted. A corrector lens is required to eliminate the remaining aberrations. Most professional telescopes—from Keck to Hubble—are Ritchey-Chrétiens. But they all use corrector lenses. It seemed to me there had to be a better way. Why design a telescope with difficult-to-make mirrors, only to have to correct it later? So I started hunting around for ideas.
This image shows the Feathertouch 3.5-inch focuser and its drive motor for autofocusing. The coiled cable allows for the focuser to turn with the instrument rotator. To the right of the focuser is the Telescope Control Panel, which operates all the electronic features. An LCD display provides a digital readout, and features are selected and controlled with the buttons and control dial.
escopes (SCTs) made by Celestron and Meade. A typical SCT uses spherical mirrors and an aspheric corrector plate at the aperture of the telescope. This design can suffer from coma and field curvature. Recently, modified SCTs have been produced which eliminate coma and minimize field curvature, making them better suited to CCD imaging. A classical Cassegrain telescope uses a
34 Astronomy TECHNOLOGY TODAY
parabolic primary mirror and a hyperbolic secondary, without a corrector lens. Like the SCT, it can suffer from coma and field curvature. As an alternative, the RitcheyChrétien design uses two hyperbolic mirrors. The trade-off can be astigmatism instead of coma, but no significant change in field curvature. Why is this an advantage? Because astigmatism, unlike coma, does not change the position of a star
A Better Way In my extensive searches of the optical design literature, I happened across a 1976 paper by Charles Harmer and Charles Wynne. In it they described a wide-field corrector for a Cassegrain telescope. Their design employed a two-element corrector lens in an afocal (zero-power) configuration. This allows the use of a single, non-exotic glass type for both elements, as there is no chromatic aberration induced. In a classical Cassegrain telescope design, recall that there can be significant off-axis coma. Harmer and Wynne pointed out that the main function of the doublet corrector was to induce negative coma of the same strength, thus eliminating coma from the final design. However, they also showed that this lens design necessarily introduces spherical aberration. A balance can be found by tweaking the shape of the secondary mirror and adjusting the position of the lenses.
DESIGNING THE HYPERION TELESCOPE For a large telescope (greater than 1meter aperture), the lenses must be kept closer to the focal plane, in order to restrict the diameter of the lenses. But the clever idea in the Harmer and Wynne paper is to point out that for smaller instruments, where the size of the lenses is smaller already, there is a position for the lenses where the secondary mirror of the Cassegrain telescope becomes spherical. When I first read the paper, it seemed to good to be true! Why had no one seized upon this idea already? A telescope that had only one aspheric surface, yet yielded amazing optical performance. Yet it appeared that Harmer and Wynneâ&#x20AC;&#x2122;s design had remained largely unknown. To me it seemed perfect, especially for amateur astrophotographers. The design should prove simple to manufacture but should give performance as good as, or better than, anything else on the market. Essentially what Harmer and Wynne were saying was that instead of correcting a telescope after the fact, like a corrected
A close-up of the Telescope Control Panel. From left to right are the focuser port for an optional piggyback instrument, the focuser port for the Feathertouch 3.5-inch focuser, the mode and select buttons for the digital readout menu, and the control dial. Below is the power button and 12-volt power input.
Astronomy TECHNOLOGY TODAY
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DESIGNING THE HYPERION TELESCOPE
The complete telescope shown on an Astro-Physics 1200GTO mount. Attached is an Apogee U16M camera, Apogee filter wheel, Astrodon MonsterMOAG off-axis guider, and SBIG ST-402 guide camera.
RC, you could integrate the corrector right from the start and get the same performance with simpler optics. They pointed out that the drawback was larger lenses (because the lenses sit farther up the light path, toward the secondary mirror), but in an amateursized instrument, this was no big deal. For example, a typical 12.5-inch corrected RC uses 70-mm diameter lenses. The Hyperion uses 100-mm lenses. The cost difference is negligible, especially in light of how much less expensive the mirrors are to make in the Hyperion. (Also, some of the extra size of the Hyperion’s lenses come from the fact that the telescope is designed to deliver a 70-mm
field, compared to the 52-mm field of most other telescopes.) Standard Features As the design of the Hyperion progressed, it became apparent that we had the opportunity to incorporate some unique features. The design had sufficient backfocus to allow the use of an instrument rotator for framing and for finding a guidestar, something essential for remote imaging. So, we thought, why not build in our own rotator? It would allow for a much cleaner, lower-profile design, and we could be assured that the rotator would be compatible with the large field of the Hyperion (and the heavy weight of the camera equipment that would surely be placed on it). The Hyperion rotator uses a custom-made 6-inch diameter brass gear and stainless steel worm, allowing for heavy loads and precision positioning. It also allows the full light path through the focuser. At this point we figured there was no
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DESIGNING THE HYPERION TELESCOPE
The Eagle Nebula captured with the Hyperion and SBIG STL-11000M. It is an LRGB image with exposure times of 80:30:30:30 minutes. Image by Scott Tucker.
reason not to just go all the way and include everything that was likely to be needed. An integrated telescope control panel allows manual and automatic operation of the rotator, the autofocuser, cooling fans, dew heaters, and even a secondary autofocuser for an optional piggyback instrument. The control panel integrates many of the features that have been proven in the Starizona MicroTouch autofocusers, including temperature compensation and wireless control. The whole suite of electronic features is controlled wirelessly through a tiny USB box. A single USB port controls all the features, eliminating the mess of cables normally associated with a rotator and focuser, etc. All features are ASCOM compatible and can be con-
trolled with included software or through programs such as MaxIm DL, FocusMax, ACP, and CCDAutoPilot, among others. Camera Compatibility The current state-of-the-art in CCD sensors is the Kodak KAF-16803 chip, a 16-megapixel sensor with a 52-mm diagonal size. Of course, the trend has always been toward larger sensors, and there was no reason to believe 52-mm would be the upper limit. It was apparent that the Harmer-Wynne design lent itself well to a very large field of view, so we decided to optimize the design for as large a sensor as was practical, given the constraints of baffling and central obstruction size. We settled on a 70-mm optimized field, with a larger field possible with only slight image
degradation. Over an 84-mm field, the Hyperion still outperforms most other instruments over a much smaller field. And indeed, larger sensors are just now becoming available to amateur astrophotographers, with Kodak releasing 39-megapixel and 50-megapixel sensors with 62-mm diagonal size. Reality It is, of course, one thing to design a telescope on the computer, and quite another to actually build the instrument. The first step was to have the mirrors and lenses made, then to test them in a prototype telescope where we could do without the fancy electronics and carbon fiber tube. Once the optics were available, we put together a basic framework to hold
Astronomy TECHNOLOGY TODAY
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them in place and headed out under the stars. A quick tweak of the collimation and mirror spacing showed that we had designed a fully functional telescope. Next, we attached a CCD camera and took some test images. All looked great. The Hyperion was born! Then came the process of designing and building the final production telescope. Feedback from potential buyers directed our design. Many high-end astrophotographers are now automating their imaging, allowing something that was once rare in this hobby: sleep. The Hyperion was designed for complete automated operation. All the features are compatible with automation programs like ACP and CCDAutoPilot. They can also be run manually - either from the control panel on the scope or through included software - for those hardcore imagers who still think sleep is for the weak. The integrated features of the Hyperion make it easy to use, but give it powerful capabilities. The electronic features are all ASCOM compatible, making it simple to integrate the telescope with automated observing software such as ACP and CCDAutoPilot. All of the features are controlled by a small wireless control box which plugs into the PC with a single USB cable. Using the Hyperion The usual procedure for starting up the Hyperion begins with activating the cooling fans. Watching a star at full resolution with short exposures on the computer screen, you can see the effect of the fans almost immediately: the star settles down to a nice point as the fans bring the air inside the telescope to the ambient temperature. There are temperature sensors for ambient temperature as well as the temperature of each mirror (primary and secondary). Focusing can be done manually through the telescope control panel, but the best way (and most fun!) is to watch the freeware FocusMax work its magic.
DESIGNING THE HYPERION TELESCOPE
USING THE HYPERION The integrated features of the Hyperion make it easy to use, but give it powerful capabilities. The electronic features are all ASCOM compatible, making it simple to integrate the telescope with automated observing software such as ACP or CCDAutoPilot. All of the features are controlled by a small wireless control box which plugs into the PC with a single USB cable. The usual procedure for starting up the Hyperion begins with activating the cooling fans. Watching a star at full resolution with short exposures on the computer screen, you can see the effect of the fans almost immediately: the star settles down to a nice point as the fans bring the air inside the telescope to the ambient temperature. There are temperature sensors for ambient temperature as well as the temperature of each mirror (primary and secondary). Focusing can be done manually through the telescope control panel, FocusMax integrates with the Hyperion autofocuser and imaging software such as MaxIm DL. A quick learning session teaches FocusMax how to precisely focus the scope. Thereafter, autofocusing is done in a matter of seconds. The focuser on the Hyperion is a Starlight Instruments 3.5-inch Feathertouch focuser. A coiled cable runs from the control panel to the focus motor, allowing plenty of room for motion as the instrument rotator turns. And speaking of the instrument rotator, this component is largely what makes automated imaging possible. For automated imaging, the user selects an orientation for the camera, sometimes for framing the subject, but most often for finding a guidestar using an internal
but the best way (and most fun!) is to watch the freeware FocusMax work its magic. FocusMax integrates with the Hyperion autofocuser and imaging software such as MaxIm DL. A quick learning session teaches FocusMax how to precisely focus the scope. Thereafter, autofocusing is done in a matter of seconds. The focuser on the Hyperion is a Starlight Instruments 3.5-inch Feathertouch focuser. A coiled cable runs from the control panel to the focus motor, allowing plenty of room for motion as the instrument rotator turns. And speaking of the instrument rotator, this component is largely what makes automated imaging possible. For automated imaging, the user selects an orientation for the camera, sometimes for framing the subject, but most often for finding a guidestar using an internal guide chip or off-axis guider. This selection is made in a program like TheSky and is output guide chip or off-axis guider. This selection is made in a program like TheSky and is output to ACP and CCDAutoPilot. When the telescope is sent to the target, the rotator moves the camera to the proper orientation. Precision of the rotator is very high, which is essential for reacquiring a guidestar when the telescope flips from one side of the meridian to the other. It is also critical for keeping the diffraction spikes aligned on opposite sides of the meridian. It is also possible to operate the rotator manually through the control panel. Once the target is found, framed and focused, and the guidestar is acquired, imaging can begin. Typical subframe exposure times are 10 to 15 minutes. As usual with deep-sky photography, as
to ACP or CCDAutoPilot. When the telescope is sent to the target, the rotator moves the camera to the proper orientation. Precision of the rotator is very high, which is essential for reacquiring a guidestar when the telescope flips from one side of the meridian to the other. It is also critical for keeping the diffraction spikes aligned on opposite sides of the meridian. It is also possible to operate the rotator manually through the control panel. Once the target is found, framed and focused, and the guidestar is acquired, imaging can begin. Typical subframe exposure times are 10 to 15 minutes. As usual with deep-sky photography, as many subframes as possible are taken to reduce noise and enhance detail. The focal length of the Hyperion is a good compromise between high-resolution detail and wide field of view with a typical largeformat CCD, making it well suited to a variety of targets. many subframes as possible are taken to reduce noise and enhance detail. The focal length of the Hyperion is a good compromise between high-resolution detail and wide field of view with a typical large-format CCD, making it well suited to a variety of targets. The production Hyperion was unveiled at the 2009 PATS astronomy show in Pasadena, CA. The feedback was immediate and very positive. The first deliveries began shortly thereafter, and the new owners also had great responses to their new telescopes. We were pleased when Sky & Telescope magazine recognized the scope with a Hot Product award for 2010. Seeing our dream telescope take shape has been an amazing experience.
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EXPLORE SCIENTIFIC
127 ED
By Craig Stark
Last summer while on my second trip to the Julian Starfest here in southern California, I got a chance to spend some time with Scott Roberts of Explore Scientific as we were both staying in the Big Cat Cabin at Chuck Kimball’s Artists’ Loft B&B (both the star party and Artists’ Loft get a big thumbs up, by the way). While there, I was checking out the David Levy MakNewt they have and we got to talking about doing a review of it and/or their flagship scope, the 127 ED Triplet APO. Up for review here is the latter.
Before we delve into the meat of the review, there are a few things worth noting and clearing up. First, while I’ve met and spent some time with Scott, Russ, Jamie and the rest of the crew at Explore Scientific (their office is just down the road from me), I’ve got no specific interest in the company. Second, while I picked the scope up from them personally, this is, effectively, a random sample. When their scopes arrive, Scott and his crew unpack them and give them a series of tests to make sure that nothing bad happened on the long trip.
Scott had called to let me know that a new batch was in and that I could stop by to pick one up some time in the next few days. When I arrived, an employee was unpacking scopes and checking them out (mechanical and artificial star tests) and was about halfway through a large stack. I got the one he’d just finished and even I didn’t know exactly when I’d make it there to pick one up. So, this was as random a selection as we could hope for here. Third, it’s worth pausing on this. Every scope is
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EXPLORE SCIENTIFIC 127 ED
Image 1 - Scope and included accessories
unpacked and tested before it is sent to the warehouse. That’s not something you see every day. 127ED Overview The 127ED is a 127-mm, f/7.5 (952mm focal length), air-spaced triplet refractor that uses a third element of HOYA FCD1 ED glass to improve color correction over an achromat that currently goes for $1999. The package comes with a 2-inch 99% reflective dielectric diagonal, an illuminated 8x50 finder scope, a Crayford focuser with a 10:1 fine-focus knob, a user-adjustable lens cell, a removable dew shield, and a solid
transport/storage case (Image 1). For mounting purposes, it comes with a set of rings that form a cradle when the Vixenstyle dovetail and handle are attached. The latter feature is something I’ve not seen often, but is a welcome addition. Riding atop the rings is a removable handle that doubles as a place to mount a guide scope (as you can see in the photo, there’s a slot in the handle for screws to pass through). It comes with a one-year warranty that can be extended to five years with registration. Now, I’ve never considered myself a “refractor guy.” I’ve had a few in my day for sure, but I’ve never identified myself in that
way. Any time I’ve gone for something more than 4-inches, it’s had a mirror and even those 4-inch scopes (my current Borg 101 ED and a TMB 105/650 LW I used to have) have been short focal length instruments. Come to think of it, no refractor I’ve ever owned has had more than about 650 mm of focal length (WO 66, Orion ST80, TMB 80SS, and SV Nighthawk rounding out the 3-inch and below crowd). So, to me, a 5-inch f/7.5 is a pretty big refractor. Add to this the mantra on various Internet groups that this is a lot beefier than a popular 120ED scope and I was expecting to be stunned by the size.
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EXPLORE SCIENTIFIC 127 ED Stunned is the wrong word, though. Impressed? Sure. It’s a lot bigger than the bantam-weight Borg 101ED I use (typically run at f/4) and nobody would call it “small.” But, potential customers needn’t be all that concerned with the size on many popular mounts. In its shortest configuration (with the dew shield removed), it’s about 33.5inches long (with the dew shield attached it extends to 42-inches long). The bare OTA clocks in at 12.8 lbs. Add the dew shield and you’re up to 15.8 lbs. Toss in the rings and dovetail and you’re at 18 lbs. Get it fully loaded with the finderscope and diagonal and you’re right at 20 lbs. This is all right on par with typical 8-inch f/4 - f/5 scopes. Unlike those options, if you’re really concerned with weight (e.g., if I were imaging with this on my previous mount, a Tak EM-10), you could replace the 3 lb dew shield with a piece of Kydex and be ready to image in 15 lbs. Included Accessories One of the things that struck me about the 127ED (and the Levy Mak Newt I got to play with for a bit) is that it’s almost as if the manufacturer is spending a good amount of time and effort to think about what will make the owner’s experience better. Go figure! Let me explain what I mean here. First, the fit and finish are excellent. Seams are tight, the mechanicals move smoothly, and the paint job is top notch. It goes beyond that though in that the included accessories are both excellent and well thought-out. The dovetail is setup to
Image 2 - Single frames from an artificial star test (Hubble Optics 5-star artificial star) taken at best focus in the center of the frame (left), just inside this focus point (middle) and at best focus but from the corner of an APS-sized frame (right). Individual frames were taken both at prime focus (top) and with the addition of a Hotech SCA Field Flattener (bottom). The slight deviations from round here are the result of thermal effects (“local seeing” effects) and not a cause for concern.
allow you to remove cone error (4 bolts on it let you square up the OTA if needed). The finder is not only optically very nice, but its reticule is illuminated. Nice! I just love the carry handle and the fact that they thought enough to stick a slot in it that allows you to mount accessories on it. 1.25-inch prism? Nope, a solid 2-inch 99% dielectric model for the diagonal. Finally, the case is just fantastic. As I said, it’s as if they sat down to think about what the potential owner will actually do
with the scope. We’ll store it and need to bring it to a dark sky site (so a good case is a real plus). Even GOTO mounts need alignment stars (so a nice straight-through finder that lets us quickly center things is a plus). Astrophotographers will want to strap on a guide scope or piggy back a DSLR with a lens on there (so, some way to bolt something on is a real plus). Get the picture? It’s a really well thought-out package in which nothing feels cheap, nothing seems missing, and nothing seems like it needs to
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EXPLORE SCIENTIFIC 127 ED be replaced out of the box. There’s a lot of added value in the package. Focuser For an astrophotographer like me, the focuser is critical (and thus deserves its own heading). The focuser is typical of many imported scopes today, which is to say that it’s a quite reasonable Crayford style with a nice 10:1 fine-focus knob mounted on one side. Motion of the 2-inch drawtube is smooth and there are adjustments available on it to suit the tension to your needs and taste. The
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drawtube has a range of 4.75-inches and I had no troubles reaching focus with my cameras (QSI 540 wsg, Canon DSLR, and QHY 8Pro tried) at prime focus, with a HoTech field flattener in place, or with any of my eyepieces. All fittings on the focuser and diagonal come with compression rings rather than simple set screws for secure, non-marring attachment of accessories. There was never any thought of it slipping with any of the loads I put on it. Rigs like the DSLR and the QHY8 Pro were handled with aplomb. In it’s full “wsg” for-
mat (filter wheel, shutter, and off axis guider), the QSI 540 clocks in at about 3 lbs and it handled it well. With that level of load, there is a small amount of flex, but the system remained quite usable. Optics While I’m no pro at star-testing (I don’t consider myself qualified to judge a quarter vs. a third vs. an eighth wave of spherical aberration yet), I’m not entirely naive here either. The scope turned in a very nice star test. Collimation was spot on and there was no
EXPLORE SCIENTIFIC 127 ED sign of astigmatism. Diffraction patterns looked nicely symmetric with the only clear difference being the color. Inside focus, there is a blue/violet halo surrounding the yellow/ green core of rings. Outside focus, there is a yellow/green surround to the blue/violet core. At focus, stars were crisp and chromatic aberration (CA) was minimal. In typical use visually, there is no CA to worry about or become distracted with. For example, one night with an eyepiece to the scope, I was hard-pressed to detect much if anything on Vega and the lunar limb was clear (turbulence would sometimes bring a slight hue to the surface). This is no achromat. It’s not perfect, but it’s darn good. For example, on another night out, Sirius did have a detectable violet halo at best focus using my 11-mm Nagler, but it was the kind of thing you could find when looking for, but it didn’t present itself as an issue on its own. One thing to note here is that the chromatic aberration (or CA, caused by a shift in the focal position for some colors relative to others) could entirely disappear with a tiny shift of the focuser. The images of a Hubble Optics artificial star shown in Image 2 show this effect well. Here, on the left, we have the 5 stars taken at best focus where the violet halo can be seen. In the middle, the focuser has been moved in ever so slightly and the overall image is a fraction of a hair less sharp. As you can see, the image is now free of any spurious color. Astrophotographers with optics that have a curved focal plane will often focus not dead-center but a bit off-axis to split the difference and get a better image overall with the center of the frame being a bit inside the plane and the edges being a bit outside (rather than the center being at the plane and the edges being far off the plane). Instead of a focus position that varies spatially, with CA the focal position varies by wavelength. Here, the difference is small enough that many may intentionally or implicitly split the difference here and choose a focus position that brings more wavelengths very close to focus. (Of course, “best focus” is in the eye of the beholder. If we or
Image 3 - Test shot of M42 taken with the ES127 ED and a QSI 540 wsg camera using Baader LRGB filters, a Starlight Xpress Lodestar, a Losmandy G11, PHD Guiding, and Nebulosity.
Image 4 -Test shot of M45 taken with the ES 127ED and a QHY8Pro, a Starlight Xpress Lodestar, a Losmandy G11, a Mini Borg guidescope, PHD Guiding, and Nebulosity.
our cameras are more sensitive to blue and violet, the middle panel is the “in focus” image.) All this means is that if you’re using a one-shot color camera like a DSLR, you’ll probably want to check a color image when doing the final focus to make sure you’ve take out that violet halo and are more like
the middle panel. Honestly, your long-exposure shots won’t be harmed at all as they will have seeing and tracking causing more softening than that touch of focus. Off-axis, the ES127 really shines. With the focuser in the “in focus” position (left panel of Image 2), I moved the artificial star
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EXPLORE SCIENTIFIC 127 ED image to the upper-right corner of an APS sensor (Canon Rebel XSi). We can see that the stars’ focus has shifted a touch (no more violet) and that there is some distortion, but the amount is really quite small (these images are magnified considerably). This is considerably better than I had expected. Typically, as we move away from the center of the FOV, the stars will become at the very least, slightly elongated, aiming inwards. The ES127 does a very nice job at staying clean here in the corner. This was backed up by test shots of a Norman Koren MTF chart that showed a small 25% drop in the LPI that could be resolved in the corner of the frame (this is a good bit better than my Borg doublet at prime, but not as good as the Borg gets with its dedicated reducer/flatteners that take it to < 10% of a drop). What error the ES127 has here was very nicely addressed by a HoTech 2-inch SCA Field Flattener (ES has their own flattener in the works). As you can see from the bottom panel in Image 2, the corner image looks exactly like the center image. But really, the
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corner performance at prime is very good and far better than I anticipated. Real World Visual Performance Amateur astronomers can be a hypercritical bunch. If Scope A and B perform identically in all respects except that A outperforms B when Sirius is viewed at the edge of a 31-mm Nagler, we’ll often say that A is better than B. This can then go on to let us justify to ourselves why we might pay a lot more for A (for that extra bit of performance, etc.). I can certainly understand this line of thinking, but I also have a very pragmatic side (hence the software I write). So, barring attempts to make it show any faults, what is the scope like? In short, it’s a great scope. No 5-inch scope is going to let my naked eye resolve M51’s arms from my urban yard. What 5inches can do, the scope does very well. There are no annoying glares or flares from the moon or neighbor’s lights. Contrast is excellent and stars are tight and round with
no errors that draw your attention. The moon is a joy to cruise at any magnitude my skies could support. The scope mechanically and optically disappeared and I could focus on whatever I wanted to observe. Astrophotography Performance I had two chances to get out for a reasonable amount of time with the ES127 and a camera and I must say I was quite pleased with how well it performed. While many would consider some form of reducer/flattener for the scope, I wanted to see just how well it would perform at prime focus. With the QSI 540 and the QHY8 Pro, prime focus is just over 1.5-inch/pixel - a very nice trade-off between resolution, FOV, and SNR. Since time was short and the skies were bright (these are under fairly urban skies), I stuck to brighter targets. The first night out was M42 using my QSI 540 wsg and Baader LRGB filters (Image 3). The scope performed very well and had I taken the trouble to refocus between filters, the shot would have been even nicer. Stars in one corner began to get a bit distorted (I believe owing to a touch of flex with the heavy camera), but overall it did a superb job. There was a touch of CA around the brighter stars but this could be removed by shifting the overall focus slightly, by refocusing a touch for the blue filter, or by post-processing. Flats showed that the corner of my 15 x 15 mm sensor was over 90% illuminated. On a second night, I used the larger one-shot color QHY8 Pro on M45 (Image 4). Again, time was a limiting factor (I only managed 2 hours of imaging), limiting the SNR in the image. My goal wasn’t to make the prettiest shot of M45 ever made, but rather to see how well the ES127 performed. Here, you can see that there is no evidence of CA at all in the image and the stars are quite nice and round throughout (the left side is very good, although not perfect in this regard). The large halos around Atlas, Alcyone, and Electra are caused from the camera’s optical window and are not related to
EXPLORE SCIENTIFIC 127 ED the scope at all (the source of the reflections is 0.6-inches from the sensor). Flats showed that the corners of this 24 x 15 mm sensor were about 75% illuminated. Thus, the scope held up very well to the demands of astrophotography. The field is remarkably flat even at prime. Flatteners like the HoTech (or presumably the ES flattener when it comes out) do an excellent job at taking out the little that is in there (I’ve verified this under the stars as well as with the artificial star test from Image 2). Residual color was either non-existent or minimal and my only note here would be for those with heavy cameras to consider a beefier focuser. Those with DSLRs and other lighter cameras needn’t be concerned at all. Gripes Few things are perfect and, as such, there are a few usability things worth noting in the “con” category. First, I wasn’t a big fan of the dewshield and lenscap arrangement. To attach the lenscap, I found I had to remove the dewshield entirely. If the dewshield was flipped over in its storage orientation, I just couldn’t get a good enough grip to screw the metal lenscap on. The dewshield itself was very effective at keeping dew off the lens, but it is rather heavy and the remove-flip-and-screw-inplace operation certainly isn’t as easy as a sliding setup (it won’t ever slide back in the middle of an imaging session, though). Second, I found that getting my fingers to successfully clamp the diagonal solidly in place
was a hit-or-miss affair. There was never a danger of the diagonal slipping out, but I would at times think it was solid only to find it still rotated easily. This tended to happen when the screw used to clamp it in place was in a small gap between a corner of the diagonal and the drawtube. Finally, while I love the case, it would be nice if the cutouts were such that the cradle didn’t need to be in exactly the right position along the OTA for the tube to fit inside the foam. A little more leeway here to accommodate different balance positions would be nice. As you can see, none of these are exactly deal breakers. Conclusions The Explore Scientific 127ED Triplet is a great scope. In fact, if I had to have one and only one scope, this one would certainly be in the running. It’s light enough and small enough that travel to dark sites is easy and portable mounts are a real option. It pulls in a lot more light than an 80-mm job and its native focal length of 950 mm is nice both visually and photographically. Even stock it does well at astrophotography and if one were to add a 0.8x reducer/flattener to this it gets you down to f/6 and over 1.5 x 1 degrees of sky on an APS-sized DSLR. Thus, it’s a great choice if you’re going to use it visually, photographically, or both. What’s more, it’s part of an exceptionally well thought out package that comes in at a very attractive price. Explore Scientific has a winner here.
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Denkmeier Optical Goes Solar Spectrum 60 PST Upgrade By Russ Lederman
Many amateur astronomers are familiar with Denkmeier Optical and our line of binoviewers. It is a small niche market within a small niche market, but is rapidly growing. However you might not be aware that we moved to the Spectrum Thin Film facility in New York last year, which has opened up a number of great opportunities that now makes R&D work in the Hydrogen Alpha Solar Filter arena possible. One of the main reasons we joined with Anthony â&#x20AC;&#x153;Tonyâ&#x20AC;? Pirera, owner of Spectrum Thin Films, was his multitude of great ideas that promise to
bring new and innovative products to market. For those of you that have not heard of Spectrum Thin Films, it is a company with extensive experience in producing all types of cutting edge optical coatings and serves a diverse range of industries including optical manufacturers, instrument manufacturers, medical industries and military applications. Spectrum Thin Films astronomy applications include work for NASA, research observatories, and other astronomy related optics (Spectrum Thin Film optics are on board the Phoenix Mars
Lander and are used for the James Webb Space Telescope and the company will soon be working on the TMT thirtymeter telescope and the next generation National Solar Observatory). The first new consumer product to result from our partnership is the Denkmeier Optical Spectrum 60 (S60), an enhancement to the Coronado PST. More specifically, the Spectrum 60 will be the first of several optical systems we are developing that are specifically designed for the H-a solar observer. Many years ago, those viewing the Sun in the narrow spectral region of H-a (656.3nm) were part of a Astronomy TECHNOLOGY TODAY
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DENKMEIER OPTICAL GOES SOLAR
Image 1 - Four of the Design Specifications of The Spectrum Solar 60 Objective Lens
very exclusive group of daytime observers and it was our goal to bring an affordable technology for H-a observations to a broader group of observers.
One of the benefits of our partnership in developing the S60 is that Tony has done extensive past testing of the PST and his expertise made it possible to
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develop several improvements that increase the already great 40-mm diameter aperture of the PST to an even better 60mm. One of Tonyâ&#x20AC;&#x2122;s innovations in developing the S60 was in improving the image size to the Etalon, which is critical since the Spectrum 60 is f/10 and the image size to the front lens has to be tuned just right. This tuning minimizes hot spots (sometimes called sweet spots) which could happen if a wedge in the Etalon is extensive. The S60 optics were optimized using the Zemax optical lens design program (Zemax is a leading optics industry software program that optical engineers and designers around the world choose
DENKMEIER OPTICAL GOES SOLAR for lens design, illumination, laser beam propagation, stray light, free-form optical design and many other applications). During the design stage we wanted to make the background as dark as possible and reduce any secondary reflections (weâ&#x20AC;&#x2122;ve always found it quite annoying to seeing a double image of the sun!). So, with that in mind, Tony developed state of the art optics that can meet this goal. The front three elements not only make the PST into f/10 but also offer correction of the scope. Using our design software we developed the custom optical coating and optimized it to meet the requirement needed. Image 1 shows some of the design specifications that went into developing the S60. Aperture Fever Fix for the Solar Observer All of this research and development means that solar observers with aperture fever can now upgrade their PST Solar Telescopes by adding the Spectrum 60.
Image 2 - Spectrum Thin Filmsâ&#x20AC;&#x2122; Ion Beam Sputtering Machine which was used to apply the coatings to the optics of the S60.
Many observers who planned to move up in aperture to a larger telescope for H-a observations may have thought they would need to put their PST aside. With
the introduction of the Spectrum 60 we offer a means to boost the PST aperture by 50% without the need to purchase a completely new H-a telescope, thus
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DENKMEIER OPTICAL GOES SOLAR making it much easier to step up in aperture. The Spectrum 60 includes a threeelement, 60-mm aperture diffraction limited refractor tube assembly as well as an eyepiece holder module containing a 10-mm blocking filter. As mentioned earlier, all components have been designed using state of art computer software to provide optimal performance when integrated with the PST. These components are all coated at the Spectrum Thin Films headquarters using our Ion Beam Sputtering Machine (see Image 2) which deposits extremely thin single and multilayer film coatings with angstrom (one ten billionth of a meter) accuracy. All of the Spectrum 60 optical and mechanical components have been carefully designed using advanced ray tracing so that there is no vignetting and the entire light cone of the 60-mm objective glass is contributing to the solar
image at the eyepiece. Increase in Resolution Since the resolving power of a lens is related to the aperture, increasing the lens diameter will produce a more highly resolved image of a given target provided that other aberrations are not introduced when doing so. Frequently cited are the Dawes, Raleigh and Sparrow limits. These methods, sometimes used to predict the resolving power of an objective lens to separate two points of light such as the airy discs produced by a telescopic image of a double star, are based on telescope aperture and either mathematical formula or observational evidence. According to these methods used to determine resolving power, fine structure on the solar disc will be more highly resolved in a solar telescope that utilizes a larger objective lens. The value of using a larger aperture telescope is self evident and illustrated by the push for larger
diameter lenses and mirrors that permeates the astronomy equipment industry. The upgraded Spectrum 60 objective lens provides a 50% increase in aperture compared with the PST’s 40-mm lens and this means that theoretical resolution is increased accordingly. It should be noted that the PST’s internal H-a Etalon filter characteristics remains the same. While the Spectrum 60’s larger objective lens produces a higher resolution solar image, the bandpass and inherent properties of a given Etalon filter is unchanged. Certainly, a “raw image” of the Sun that exhibits higher resolution means that a more detailed image will be processed by a given Etalon filter housed within a PST. This will result in greater detail of fine features such as filamentary structure of prominences and surface detail on the solar disc, if they are present at the time of observation. Every component including the three-element 60-mm objective lens,
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DENKMEIER OPTICAL GOES SOLAR BF10 Filter and the mechanical parts have been very carefully designed for optimum performance. The 60-mm objective lens offers diffraction limited performance and the glass types have been selected for optimum transmission in the spectral region of the targeted bandpass of H-a (656.3nm) with blocking from ultraviolet to far infrared to 10^-5 to ensure the safety of the observer. The upgraded BF10 Module replaces the 5-mm blocking filter module of the PST at the eyepiece section. This 10-mm clear aperture BF filter is set in a fully machined holder. The BF10 Module accommodates the larger image size of the solar disc produced by the 60mm f/10 objective and can also be used for photography where the image scale has been increased by way of a barlow. This larger image is normally produced when a barlow lens is used to allow the camera to reach focus and the BF 10 may
be advantageous in that regard allowing a more even illumination of the solar disc. The BF10 in practice provides a larger viewable area for wider field eyepieces and accommodates the larger image scale produced by the 60-mm f/10 objective lens. An upgraded fully machined focuser knob is also included to improve ease of focusing. Since the tube assembly is now longer, we offer an optional aluminum case for the newly outfitted PST. The case comes with a high quality poly ethylene foam interior and provisions for 1.25-inch eyepieces. Those wanting a larger diameter blocking filter may upgrade to a BF15. Note that since the tube assembly is now accommodating the 60-mm objective lens, the built in solar finder located on the main block of the PST will function but the solar image on the screen of the PST finder will black out just as it is centered, therefore we also offer an optional Sol Ranger Finder from
Tele Vue. While our tests indicate that using a normal photographic tripod with the Spectrum Solar 60 and the existing PST mounting socket does not present a problem, we will offer a clam-shell mount which accommodates the Sol Ranger Finder and also features a 1/4inch mounting bolt as an option for the Spectrum Solar 60. This clamshell mount serves to aid in balancing after the PST is installed on a tripod and provide a fully functioning solar finder. A Dedicated Solar Observer’s Comments We asked Greg Piepol, a well known solar observer and imager, to upgrade his PST with the Spectrum 60 and he was kind enough to provide us his comments which are included here. He also offers a wealth of information on solar observing at his website at www.sungazer.net. From Greg, “One of the main highlights over the standard PST is the image
A big Dob on an Equatorial Platform is the ultimate observing machine. The Platform gives you precision tracking, whether you are observing with a high-power eyepiece, imaging with a CCD camera,or doing live video viewing with a MallinCam. Just check out this image of NGC3628 taken by Glenn Schaeffer with a 20-inch Dob on one of our Aluminum Platforms! Visit our website for details about our wood and metal Equatorial Platforms, as well as our line of large-aperture alt/az SpicaEyes Telescopes. You can also call or email for a free color brochure.
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DENKMEIER OPTICAL GOES SOLAR
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scale. The size of the sun’s disk is enlarged to a point where you can see large and small solar phenomena at a comfortable magnification. This has always been a complaint for me with the PST. If you magnify the view of the PST, the image dims and you lose contrast between the lighter and darker objects. Not so with the S60. The D21 gives a good low power scale that shows good disk and prom detail. The D14 (my favorite!) really enlarges the disk and keeps the contrast while magnifying the image. The S60 offers an enhanced level of uniformity of view. The PST has always had a bright spot (hot spot) in the center of the disk which is much more evident with a camera but can be seen in the eyepiece. The S60 does a great job of eliminating this spot. Perhaps it has something to do with how the rays trace now. I’m not sure. I wasn’t concerned with the hot spot at all with the S60. Also, since we’re in the solar minimum now, you really need to magnify the smaller
sunspots and proms. Adding more magnification is what most people do to get a better view. The S60’s larger aperture and better glass are the biggest assets here (along with good seeing). The S60 also offers excellent darkness around the disk which is sometimes overlooked. The PST doesn’t always offer the best contrast issues when it comes to the darkness of space and brightness of the disk. This is an area too where the S60 adds real value to the PST. It helps keep space nice and dark, shows off the disk detail, and allows subtle proms to shine through. I’m really waiting for a monster prom to appear!” We are excited about the Spectrum 60’s addition to our line of Denkmeier Optical’s products and we will be attending several upcoming events this year to let observers test out the S60 for themselves, and we hope to see you there! If you would like more information, please feel free to check out our website at deepskybinoviewer.com.
GoldFocus Focusing System A New Approach to Achieving Critical Focus By Dave Snay
We all know the trials of achieving critical focus for astro photography. At first we think our eyes are good enough to get it right. Then we see that’s not true and try various means to verify that we’ve gotten everything well tuned and ready to go. I’ve tried virtually every kind of mask referenced online, including but not limited to strings crossed over the end of the OTA, Hartmann masks and most recently a Bahtinov mask. Many data capture packages include the ability to magnify the image and I’ve even tried combining that with various masks. There is also the mystical FWHM value
that can be measured by some of the more sophisticated data capture software available. I had settled on a combination of Bahtinov mask and image magnification followed by FWHM values during data capture to maintain focus. Well those days are gone for me. Enter the GoldFocus Focusing system. It is a combination of a specialized mask and very specialized software that enables you to achieve extremely precise focus in a matter of minutes. At first glance, the mask looks much like a Bahtinov mask, but the
resemblance ends there. This mask is designed to generate a very specific pattern, see Image 1, based on extensive research by Jeffrey Winter, who just happens to hold a PhD in mathematics. I have a nephew that holds one of those degrees, and let me tell you they are incredibly intelligent people. I like to think I’m pretty smart (I am a retired software engineer and Worcester Polytechnic Institute graduate), but I rarely understand my nephew Astronomy TECHNOLOGY TODAY
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GOLDFOCUS FOCUSING SYSTEM
Image 1 - GoldFocus Spike Pattern
when he starts gettin’ all technical on me. The only folks I’ve worked with that think further out of the box than these
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guys are physicists. Debate with them at your own peril! Back to the GoldFocus system. Upon
opening the box, my first impression is that the masks are very well constructed. They are light enough that they should pose no threat to the current position of your telescope. However, they do not look fragile or cheap. They come “unassembled,” meaning you’ll have to install the three plastic screws, nuts and sleeves (which are included) that are used to hold the mask in place on the optical tube. If you read the instructions before you do this, you’ll be sure to get it right. The key is to insert the screws from the side that has the engraving. More on that in a bit. Before you put things together – I know, it’s hard to wait – install the software and read the assembly instructions, which just happen to be the first thing the software opens after installation. Installation was simple and flawless on my Windows XP system. Insert the included disk and install the software as instructed, taking all the defaults. Let it open the readme file when done. It opens it in a
GOLDFOCUS FOCUSING SYSTEM
Image 2 - GoldFocus Analysis Window
small window rather than full screen. I’m not sure I wouldn’t prefer the full screen because the first thing I did was expand the screen. As I already mentioned, the first pages are assembly instructions. Naturally I had started assembly while the software was being installed. Of course I started out on the wrong foot by attaching the mounting studs from the wrong side. It only took a few minutes to reverse the installation. After reading the user guide, I realized why it makes a difference which way you install the studs. There is an “N” on the side with the engraving that you use to properly orient the mask during use. Align this mark as closely as possible with the top of your camera, whichever way the camera is oriented. If you do this, and have checked the “Auto-detect mask at startup” option, you’ll be in better position to achieve focus quickly.
The mask’s diffraction pattern needs to be aligned with the analysis annulus presented by the software and the closer you have the mask and camera oriented, the less adjustment of the software’s Mask Rotation value you will need. If you’ve done this and still find the diffraction pattern and the annulus are not well aligned (it is easy to have things further off than you think when working in the dark with gloves) you can try selecting the “Align to Mask” option, which will attempt to align things for you. If that doesn’t get things squared away, the “Mask Rotation” value can be changed to rotate the software’s view of the diffraction pattern so that the spikes from the star are aligned with the software’s analysis zones. Once you do this, you’re on your way to critical focus in minutes regardless of whether you are using equatorial or alt-az mount. GoldFocus does not provide data
capture software. It relies on other software to provide images for its use. You simply set your data capture software to take continuous exposures and save them in an easily located “focus” folder. Then you tell GoldFocus where to find them. You select the same folder for focus analysis (the user guide explains the details better than I can) and then follow the on screen instructions. The software not only tells you how close you are to focus, but it also tells you which way to turn the focuser. You can even tell the software that it’s got the direction backwards so that it will be correct from then on. The key here is to wait for a few cycles of image capture/analysis between focus adjustments or you’ll just chase your most recent change. You can automate this process by enabling the “Track and Stack” feature, located in the “Focus Analysis” section. You can select the number of frames to
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GOLDFOCUS FOCUSING SYSTEM accumulate before each analysis and recommendation. This will help prevent chasing inconsistent seeing conditions, which can wreak havoc with focus attempts. GoldFocus does its best to choose the brightest star in the field of view for analysis. It is generally recommended that you achieve critical focus using a relatively bright star prior to composing your imaging subject for the night. That works well enough, but if you’re like me and have to adjust focus between filter changes (even parfocal filters typically require minor adjustments between changes), then it becomes more useful to focus on a star in the field of view of the target. If there is a star that dominates the field, there is no issue. However, this can be problematic if you’re working on galaxy or nebula subjects that don’t have a bright star in the field. In cases like this, the software can try to use the center of the galaxy for focus. If you’re imaging a nebula that covers the majority of your
field of view, then there may not be a star bright and/or sharp enough to use for focusing. If your data capture software is capable of saving only a portion of a frame, you’re in luck. Simply select a star within the field and have your software save only that portion of the image to the “focus” folder. Also, if you’re using a telescope larger than my 80-mm refractor, you are likely to have plenty of choices for focus within your chosen field. Jeff was kind enough to provide me with a mask for my 8-inch SCT. When I use that telescope I never have to search for a star to use for focus adjustment. In fact, the diffraction spike pattern in the larger telescope is very well defined and easier to interpret in the software’s analysis interface, as shown in Image 2. See the ”Focus OUT 0.4 pixels” text in the lower right of the window? That’s telling me I’m pretty much as close to perfect focus as I’m going to get. I found anything under one pixel yields very nice images.
One feature I find particularly useful when aligning the annulus with the diffraction spike pattern – when not using the big SCT – is the zoom tool within the Focus View. It doesn’t have any effect on the analysis, but it does allow me to see the diffraction spikes more clearly when I’m using a less than ideal star for focusing. Many users will not need this tool because they can and should use the “Auto-detect mask at start-up” option in the Focus Analysis section. If you’ve got the mask oriented relatively close to celestial north, then this option will allow GoldFocus to orient the analysis annulus (say that ten times fast) to match the diffraction pattern. If you start with that setting and the diffraction pattern you see is not well defined – usually due to using a relatively faint star – then you can zoom in and use the “Mask Rotation” tool to more properly align mask and pattern. If you need to rotate the mask, it helps to understand that the value changes are relative to the 3 o’clock
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GOLDFOCUS FOCUSING SYSTEM position on the mask. So a negative change will rotate the mask counterclockwise and a positive change will rotate the mask clockwise. There are a few other tools at your disposal in the software, but their use is beyond the scope of this review. If you’re processing your images and find yourself wondering if you could have achieved better focus, then you probably could have done so. GoldFocus is the next step in achieving and maintaining critical focus. There are a couple of enhancements I would like to see. The Mask Rotation value is numeric. I would prefer it be more intuitively labeled left and right or counter-clockwise and clockwise. I would also like to see the software made capable of determining which way you need to adjust the focuser regardless of the type of telescope system you are using. As it is currently implemented, you might have to tell it to reverse its recommendation of in and out of focus depending on whether you are using a reflector or a re-
fractor. It might be possible to determine that if the software is given the configuration of the current hardware. However, if you consider the myriad configurations possible I think you’ll agree that it’s better that they focused their attention on the analysis requirements. Both of those enhancements truly are nit picking, but that’s all Jeff has left for me to complain about. He has done a very nice job of producing a tool for us in GoldFocus and it is also very reasonably priced at between $70 and $145 depending on the size mask you require. There are sizes from 2.5-inches up to 17.8inches. They can also make custom sizes if you have needs outside these ranges. Unlimited technical service is available, but I really can’t imagine why you would need it. GoldFocus is extremely easy to use and the documentation tells you all you need to know for success. It is concise and crystal clear. You can learn more details and order your copy at http://www.goldastro.com/goldfocus/.
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A Technique for Creating Excellent Flat-Field Images By Rich Williams
At the Sierra Stars Observatory Network we have a reputation for delivering high-quality image data to our customers. We automatically post-process the raw image files to apply bias, thermal, and flatfield calibration files to the data we deliver. Many of our customers tell us that our data is the “smoothest” and cleanest they have seen. Ultimately the key to our success in creating such low-noise, clean data is the application of the flat-field technique I developed for our Sierra Stars Observatory (SSO) in Alpine County, California. The same technique is now also used for the SSON Rigel Telescope at the Winer Observatory in Arizona. There are three types of noise in astronomical CCD imaging that you must strive to eliminate to achieve the highest possible signal-to-noise ratio (SNR) from your raw image data. The noises are caused by electronic, thermal, and optical factors, which are corrected by the application of bias, thermal/dark, and flat-field calibration images respectively. Most of the higher-end astronomical CCD cameras sold today are capable of cooling 40 to 70 degrees Celsius below the ambient temperature and are well-filtered to reduce electronic noise. Therefore, applying an appropriately combined series
Image 1
of bias and thermal/dark frames to the raw data from these cameras typically does an excellent job removing electronic and thermally induced noise. At SSON all calibration series are median-combined to create the master calibration frames. Achieving high-quality consistent flat-field calibration images is not as simple as it might seem at face value. The basic idea is simple enough: take a series of images for each filter of an evenly-illuminated “area” with little or no light gradient. However, it is harder than it sounds. I considered two flat-field techniques
to use for calibrating SSO image data: Twilight Flats and Dome Flats. I spent a few months experimenting with various flat-field techniques using the Sierra Stars Observatory before I developed the technique we use today. I extensively searched the web for references about flatfield techniques used by professional and amateur observatories. At first it seemed that the simplest and easiest to implement technique was to take twilight flats and I spent many nights experimenting with the twilight flat-field technique. My results were inconsistent and the experience was somewhat frustrating. No Astronomy TECHNOLOGY TODAY
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A TECHNIQUE FOR CREATING EXCELLENT FLAT-FIELD IMAGES matter how hard I tried I could not seem to get enough images for each filter without star trails. I did manage to get some usable sets of flats, but the results were disappointing and felt I could not take a chance on using this technique for SSON. That left dome flats as the only viable alternative. In doing my research on dome flats I read about various different screens and lighting configurations used to try to get even illumination, proper spectral response, and so on. I experimented with various types of incandescent, halogen, and diode lights to illuminate a white poster board. I also set up devices to orient the lights at various angles and orientations to try to eliminate the inevitable gradients that formed. Even when the board looked evenly illuminated to my eye there were unacceptable (at least to me) light gradients in the resulting flatfield images. In addition, it proved hard to find a multispectral light source with the appropriate intensity I needed. Even
Image 2
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A TECHNIQUE FOR CREATING EXCELLENT FLAT-FIELD IMAGES so I did manage to find a compromise that gave me OK results but still fell well short of the professional high-quality data I wanted to deliver to customers. Finally one day it occurred to me that the solution to my problem was to combine the best properties of twilight flats and dome flats into a single technique. In retrospect it was an obvious idea. That afternoon, using electrical tape as a quick and dirty method, I mounted the poster board I was using for flats on the dome opposite the shutter opening. At sunset I opened the dome and pointed the shutter at the azimuth of the setting sun and then pointed the telescope at the center of the board. As twilight set in I started taking images using the clear filter slot until I could take exposures long enough to not show a gradient effect from the opening shutter, which proved to be exposures of 2 seconds or longer. The results were better than anything I was getting from previous techniques! After this initial success I decided to
build a permanent setup to use this technique for all our flat-field work. After a little more testing I found that the poster board was a little too glossy and imparted a slight glaring effect in part of some of the flats. Also I wasn’t certain that the board was evenly reflecting light across the entire spectrum. During my research I read about paint for projection screens that reflect light evenly across the visible spectrum produced by Goo Systems (www.goosystems.com). I ordered enough of the basecoat and topcoat product to cover a square meter area. The cost was about $140 USD. From my experience with a screen with a glossy finish I decided that I wanted something with a more matte finish that would better diffuse light. I went to home building supply stores and large shopping complex in Carson City, NV to look around and try to get an idea for something that would fit my needs. When I went into an art supply store I found what I was looking for – an artist’s canvas
mounted on a simple wooden frame. The canvas was designed to be painted and the finish gave the right amount of matte I was looking for. I also bought some ultrablack paint to apply around the edges to reduce glare around the edges. After painting the canvas with the special screen paint and mounting the screen on the dome opposite the shutter I was ready to start testing out the new system. It took several nights of trials to figure out the optimum process for creating the best flat-field images. Image 1 shows the SSO flat-field screen mounted on the dome opposite shutter. What I Learned I learned a lot about how to create high-quality flats from my research and testing out my ideas. The keys to success for creating excellent results are listed here. Even illumination with natural light of a surface that reflects light evenly through a broad spectrum. Orienting the
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A TECHNIQUE FOR CREATING EXCELLENT FLAT-FIELD IMAGES screen towards the azimuth of the setting sun fully and evenly illuminates the screen with the ambient light from the night sky. The broad-spectrum reflectivity of the painted screen provides the same spectrum of the night sky for all filters. There is no problem with stars affecting the images or a sky gradient effect as there can be with twilight flats taken directly of the sky. Also this technique works equally well for clear or cloudy skies. Exposure times long enough to not show a shadowing effect from the camera shutter. CCD cameras that use shutters create flat-field images with noticeable geometric gradients when the exposure times are too short. The reason being that parts of the CCD chip are exposed for relatively longer times. For example, the FLI Proline camera used on the SSO and Rigel telescopes uses a multi-vane, iris-type shutter. With this system the center of the chip is exposed first and last as the shutter opens and closes. For flat-field exposures of one second and less you can see a no-
ticeable brighter “starfish” pattern radiating from the center of the image. I found that two-second and longer exposures do not noticeably show this affect on the SSO telescope. The actual time required to eliminate this effect likely varies somewhat for other systems depending on telescope aperture, sensitivity of the CCD chip, type of shutter, and so on. Take as many flat-field exposures as possible for each filter. Unlike bias and thermal images, flat-field images using ambient twilight light for illumination need to be taken quickly at very specific times to achieve optimal results. This is the trickiest part of the flat-field process. As noted earlier exposure times for each filter need to be long enough to not show the “shutter effect,” but they also need to be short enough to get at least several exposures for each filter to combine them to get a high-quality master flat. Experimenting with the setup on the SSO 0.61meter telescope I found that I could take 10 four-second exposures for each of five
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filters within the window of opportunity. Four-second exposures with this system have little noise. Master flats for each filter are created by median combing each 10-image series. Make sure the average ADU count in flat-field image data is high as possible. This important requirement for achieving the highest quality flat-field images appears to be not widely known or applied correctly by many CCD imagers. I too was ignorant about the correct “setting” for the saturation of the Analog-toDigital Unit (ADU) level for flat-field images until I read papers by Richard Crisp and other CCD engineering experts on this subject. From a practical standpoint for this discussion ADU counts are the integer values of pixels you can read and display with almost any software used for astronomical image processing and analysis. These ADU integer values represent a measurement of how full the well of each pixel is from collecting photons or to put it another way how “bright” the pixels are. Most of today’s CCD cameras used for astronomy have 16-bit electronics and CCD chips with pixel ADU counts of approximately 65k, where an ADU value of 0 is completely devoid of any measured photons (typically black on a computer monitor) and a value of ~65k is completely saturated from measured photons (typically bright white on a computer monitor screen). The slope of the measured ADU counts (values) for most CCD cameras is typically very linear until you approach the highest measurement values (approaching 65k). At some point the nice straight linear slope starts to deviate ever so slightly. At this point the measurement slope becomes non-linear and pixel measurements beyond this point (higher values) will not have the exact same measurement relationship accuracy as the linear part of the measurement slope. This is important to understand when taking precise scientific measurements and you want to measure your data in the linear
A TECHNIQUE FOR CREATING EXCELLENT FLAT-FIELD IMAGES range of the ADU counts. To achieve the highest-quality flatfield images you should strive to set your exposure times so that the ADU counts in the images are as close as practical to the point where the measurements become non-linear, but not over this threshold. The specification of the KAF 09000 CCD chips on the SSO and Rigel CCD cameras show that the ADU counts are linear until the about 56k (out of ~65k). Therefore, I start taking the series of flat-field images for each filter when I measure the center of the image (typically where the ADU count is highest) to be 55k. The master flats from the 10 median-combined images end up with an ADU count between 40k and 45k. Image 2 is a master flat-field calibration image for the C filter of the SSO telescope. The image is nicely illuminated with less than a 10 percent gradient from the brightest to the darkest parts of the image. The image is stretched to
exaggerate the lightest and darkest areas of the image, which shows that even at four-second exposures the center of the image is slightly brighter than the edges. A Typical Calibration Session at the Sierra tars Observatory Our SSO observatory control system software suite, Talon, has an excellent camera control program (called Camera) with utilities for creating calibration sets. I take new sets of both bias and thermal calibration images at the start of each calibration session. I can start taking these images anytime after the CCD camera is cooled to the desired temperature (typically -35C or -40C). The procedure for running a calibration session is a follows: 1. Run a series of 20 bias images, which are then automatically mediancombined to create a bias master frame.
2. Run a series of 20 thermal (dark) images, which are automatically median-combined to create a thermal master frame. 3. Shortly after sunset open the dome shutter and set the shutter to point to the azimuth degree setting where the sun set. 4. Slew the telescope to center on the flat-field screen located directly opposite the open shutter. 5. Select the B filter for the first flat field run. 6. When the sun is approximately 1 degree below the nominal horizon, start taking short-exposure images to monitor the ADU count until the count drops to ~55k for a fourminute exposure. 7. As soon as the proper ADU count is reached run a series of 10 fourminute exposures for the B filter, which are automatically mediancombined and processed to apply the bias and thermal master frames
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A TECHNIQUE FOR CREATING EXCELLENT FLAT-FIELD IMAGES to create a flat field master frame. 8. Repeat steps 5 through 7 for the V, R, I, and C (clear) filters respectively in that exact order. The timing for running the flat-field steps is critical and requires concentration. The windows of opportunity are short and a mistake can ruin the entire run. For the SSO telescope the ADU count is optimal for taking the B filter flat-field images when the sun is approximately 2 degrees below the nominal horizon (measured by the control software). The filters must be run in a specific order (B, V, R, I, and C) to achieve the desired ADU count for each filter. The reason being that each filter reaches a ~55k ADU count for a four-second exposure at different sky brightness. For the SSO set of filters the B filter requires the longest exposure time to reach a specific ADU count at a particular sky brightness while the C filter (no filter) takes the shortest time to reach the same ADU count for the same sky brightness. The V,
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Astronomy TECHNOLOGY TODAY
R, and I filters require incrementally shorter exposure times than the B filter for the same sky brightness to achieve an equivalent ADU count. Because the evening twilight sky is continually getting darker as the sun sets farther below the horizon you need to take flat-field images starting with the filter that is least efficient and collecting photons and end with the one that is most sensitive. Running the sequence in the correct order is critical for completing all the flat-field images in the short time available. If you take your flat-field images in the dawn twilight instead of at dusk, you must reverse the order of the filters as the sky will be getting brighter instead of darker. Results I spent over a year developing and refining the calibration and flat-field techniques and procedures described in this article. I am very happy with the results we get using this system. We continually
get rave reviews from our customers about the quality of our data. The majority of our customers do scientific astrometry and photometry projects. The calibration technique I describe enables our customers to get the most from the raw data we collect and deliver to them. The techniques and procedures described here for the Sierra Stars Observatory will work for any setup with a few modifications. For example, for a roll-off roof or transportable telescope a flat-field screen can be oriented to face west towards the setting sun to achieve the same result as the one mounted in the SSO dome. Different telescope/camera/filter combinations will likely require different exposure times, have different ADU linearity specifications, and so on. A little experimentation will determine the optimal setting to achieve excellent flat-field images for any configuration. If you have any questions about the these techniques please feel free to email me at contactus@sierrastars.com.
Powering a DSLR Use the Same 12-Volt Source that is Probably Powering Your Telescope and Other Equipment By Rick Saunders
Most DSLRs these days come with a fairly high-capacity battery of some sort (there doesn't seem to be a standard) which will last for many hundreds of normal, terrestrial “snapshots.” For the astrophotographer though, the shot count that shows up on the specification pages for the camera means very little. In this article I’ll be discussing powering your DSLR from the same 12 volt source that is probably powering your telescope and other equipment. The cameras I use are the Canon EOS Rebel series, but this can be translated into any DSLR. The first thing that has to be taken into account is the voltage requirements of the camera. These are generally fairly wide as internally, the camera is probably
running 1.8v, 3.3v and perhaps some 5v parts. These are supplied by on-board regulators. Most of the regulators these days want about 2.4 volts above the output voltage needed; for example, a 5v regulator needs 7.4v. For the Rebel series, the batteries are rated at 7.4v while the camera is marked 8.1v. I supply around 8v and they work just fine. So, we have to turn 12 volts into around 8v to provide to the camera. The simplest way to do this is to use a linear voltage regulator. There is an 8v regulator on the market known as an LM7808 which will take our 12v input down to around 8v or there is another regulator called an LM317 that will do the job as well. The LM7808 uses less parts but dissipates more heat than the LM317. This
is a bit of an issue, but not too much. The voltage “lost” with either regulator when we go from 12 to 8 volts is dissipated as heat. How much heat depends on the current draw and how much voltage drop we are talking about. As my cameras generally draw < 200mA with the shutter open the heat isn’t much of an issue. Both of these parts come in what is known as a TO220 package. These are hefty, three-legged parts with a metallic 'tab' that allows a heat-sink to be screwed to them. Image 1 shows what they look like (a bit enlarged) and what the legs are for. The “tab” with the hole is connected to the centre leg. Keep that in mind. The parts are pretty durable and will stand up to temperature and moisture well. Both are very stable and will provide Astronomy TECHNOLOGY TODAY
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POWERING A DSLR
Image 2
Image 1
enough current to run your camera. If you are worried about heat dissipation go with the LM317 circuit. It can provide 50% more current than the 78XX part and dissipates less heat. The LM7808 is a fixed voltage regulator that takes anything from 10.4 to 40 volts and outputs a nominal 8. Mine runs at about 7.95 which isn’t an issue. It only needs two external parts to function; two filtering capacitors. (Some people don't use them...I do, they are cheap.). A circuit diagram is shown in Image 2. As you can see, it is extremely simple and can be put together with no circuit board. The 12v positive input connects directly to pin 1 on the LM7808 (Vin) and pin 3 on the regulator (Vout) is connected to whatever you want to use to attach the camera. The input and output share a ground and two capacitors are added to filter out noise. The LM7808 series will allow a maximum of 1 ampere of current. This much draw would require some heat-sinking though. The 78XX series chips can get really hot at those current levels. I don’t put a sink on for my camera power circuits. The heat sinks are only a few pennies so if you wish to use one, or just use a bent piece of aluminum sheet, feel free to do so. For cameras that don’t use 8V the LM78XX chips come in 5, 6, 8, 9 and 12 volt versions. If you need something else,
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fear not. The second option of using the LM317 is for you. These are adjustable output voltage regulators that you can set to pretty much Image 3 what you want. The LM317 is the same size and form part as the LM78XX. It has three legs but these are Vin (voltage input), Vout (voltage output) and Adj (adjust). This chip requires a couple more parts to function, but only a couple more. Note the Image 5 diagram in Image 3. The two resistors that run from the output leg of the regulator to the ground through the adjustment leg determine the output voltage. The first resistor, labeled 220R (or 220 ohms) is fixed. The datasheet calls for a resistor from 200-240 ohms. The resistor labeled R2 is selected for the required output voltage. The calculation for this is (as close as darn is to swearing) as follows: Vout = 1.25 *(1 + R2/220)+( .000001* R2). If you're using a 200 or 240 ohm resistor then change the values accordingly. Image 4 features a short table of various R2 resistors. Note
that the LM317 needs 3V of overhead. Both of these circuits can be modified to provide “brown-out” protection for those high-current times when the shutter is snapped open. Just add a 200 ohm electrolytic capacitor on the output side. Also, if you are of the paranoid persuasion you can protect your voltage regulator against nasties by putting a reverse biased 1N4002 diode across it from the output to the input. Image 5 is a circuit diagram that shows the LM7808 circuit with the protection diode and the 200uF capacitor to hold the voltage up. Both of
POWERING A DSLR these can be considered optional. You have to have some way of connecting your new power supply to your camera. What we’re trying to do is to replace the on-board battery, so it makes sense to have something that slips into the battery compartment. With my old Rebel 350D a battery-shaped part was easy to machine from plexiglass while using some brass shim material for contacts. With my new Rebel 500D this isn’t an option as the battery format has changed. You can do a couple of things here. The first is to buy an after-market battery (not an expensive name-brand replacement) and gut it to wire up your eliminator. This is again simple for some cameras but not for others. The second route is to buy an after-market (or name brand) AC adapter and modify it. After trashing a perfectly good battery to build one for my Rebel 500D, I bought an inexpensive AC adapter from a discount battery place and went with it. The modification is simple. We want allow the power deliver end of the AC adapter (or home-made solution) to plug into our voltage regulator. I’ve found that the best connector for this is a simple 3.5mm mono phone plug. While they do short when inserted or removed, they keep a fairly positive contact and are better than something like an RCA. I cut the output line on my AC adapter and put a 3.5mm male on the delivery end and a 3.5mm female on the adapter end. As my regulator has a 3.5mm female
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R2 Resistor 680 ohms 820 ohms 1000 ohms 1200 ohms 1500 ohms
Output voltage 5.11 volts 5.91 volts 6.93 volts 8.07 volts 9.77 volts
Image 4
my modded cable can now be used for my DC solution or with the AC adapter. You can tell from Image 6 that this solution is very clean and provides no problems at all. A bonus is that my old home-made eliminator for my 350D will plug in and allow me AC power for it as
well. It’s good to “standardize.” That is about all I really need to say. Being able to power my camera from a high-capacity source gives me the peace of mind of knowing that when it is cold out and I'm doing a long series of subexposures I don't have to worry about my camera battery dying.
Image 6 - 3rd party AC adapter for Rebel T1i
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Unihedron Sky Quality Meter-L How Dark is Your Sky? By Erik Wilcox
I love electronic gadgets. All the better if they’re related to astronomy. I first used a Unihedron Sky Meter about three years ago when an observing partner brought one to a star party. I immediately forgot about the “gadget” part of the SQM, as the unit proved to be incredibly useful and effective! When we discuss observing sites, the first question that usually comes up it is “how dark are the skies?” In the past, such a determination was always extremely subjective. Everyone’s eyes are different, and a “Magnitude 6 Sky” to one person’s eyes might be 5.5 to another. There’s also the issue of changing sky conditions over different nights (or even hours), and over time as light sources degrade sites. As I’ve gotten older, I’ve noticed that my eyes take longer to dark adapt and it’s sometimes more difficult for me to see faint
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stars that used to be easy, so my eyes sometimes “lie” to me about how the dark the sky is. These examples are just some of what makes the Unihedron Sky Quality Meter so useful. I purchased the Unihedron Sky Quality Meter-L at Scope City about two years ago. The “L” stands for “lens,” as the SQM-L has a narrow lens, which measures the brightness of a sky in a 30 degree “cone.” The older SQMs have a wider FOV of about 80 degrees. Why is this important? At observing sites with ambient light pollution, the wider cone may pick up some of the ambient light. I’ve used both units and while they each work exceptionally well, I prefer the newer SQM-L for that reason. In fact, I’ve found that at poor sites, the SQM-L
consistently gives slightly higher readings, which I assume is because it’s not picking up as much ambient light pollution as the older unit does. I haven’t had the opportunity to compare the two at a dark site, so I can’t say whether that’s the case at every location. The SQM-L is very simple to use. It’s powered by a 9 volt battery (which lasts a long time) and has a “Start” button to begin sampling the sky. The unit then sounds an audio “chirp” noise until it is finished sampling. For bright skies, a read-
ing pops up almost instantly. For dark skies, it can take just over a minute. The measurements are in magnitudes per square arc second, but can be converted to NELM by using a simple online calculator on Unihedron’s website, specifically at: http://unihedron.com/projects/darksky/NELM2BCalc.html. There’s also a very useful conversion graph on their site which I’ve printed and always keep handy in my eyepiece case. It can be found at: http://www.unihedron.com/projects/dark sky/images/MPSASvsNELM.jpg. However, after using the SQM for awhile, MPSAS becomes an easy measurement to get used to. There’s also a handy temperature readout, in both Celsius and Fahrenheit which can be accessed by simply pressing the “Start” button once more after the sky sampling is complete. The unit also has an Infrared Blocking Filter which is said to restrict measurements to only the visual bandpass. The SQM-L is physically small; about the size of many cell phones. It easily fits in a pocket or in the corner of an eyepiece case. The readout is in red, and is easy to see even during daylight; yet it automatically dims for use in dark skies so your night vision won’t be ruined. It also automatically shuts off once activity stops so there’s no worrying about the unit being left on. How does it work in real conditions? Very well. I’ve used the SQM-L at dozens of locations over the past couple of years, and I’ve found it to be very accurate. Just as importantly, I’ve found it to be accurate when I’ve had the opportunity to compare it with other units (though, as I mentioned earlier, the newer SQM-L samples a smaller portion of the sky and thus can give a slightly higher reading at a site with ambient light pollution versus the SQM). Part of the beauty of using SQMs is to be able to share data about a site with other astronomers. If SQMs weren’t accurate, this data would be useless. When I’ve compared the readings I get to how deep I can visually see with
fully dark adapted eyes, the results are right on. For example, on a clear moonless night in my backyard, I usually get readings of around 22 when pointed away from the Milky Way. That translates to a NELM of about 6.6, which jibes with what I can see visually with my naked eye under perfect conditions. In addition to the SQM-L and SQM, Unihedron also offers an Ethernet enabled SQM (SQM-LE), and a USB connected model; the SQM-LU. They even sell a weatherproof housing for permanent applications. My experience is limited to the SQM and SQM-L so I can’t comment on the other models. I’m very happy with the Unihedron SQM-L. It’s a reliable and useful tool for measuring the sky brightness at any location. For the price of an inexpensive eyepiece, it’s an incredible value. Due to its small physical size, it can be taken anywhere. And most importantly, it provides a solid number of what the skies at a given location are really like.
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ASTRO TIPS tips, tricks and novel solutions
Drive Your LightBridge or Other Dob With a SkyScout By Robert Stelmock I’ve been in and out of astronomy for over 50 years. My journey began with a 3-inch cardboard reflector, then I moved up to a Jason 60-mm refractor and polar mount at the age of 12. I loved to just look up and pan the sky, but never took the time to learn the night sky. After retirement I had more time for hobbies, bought a Meade LX200 and ETX90, and just love the go-to stuff. I also joined an astronomy club, MARS in Tampa, and my obsession truly began. During the last few years I bought a POD, mounted the LX200 in it, and thought I was in heaven. But my home skies are not dark at all. I get some good nights, but not often. So I travel to dark skies sites like many do and I bought a 12-inch LightBridge to take along. Going to dark-sky sites has been very rewarding – wow, look at all those stars! Oh, but which are the guide stars I need to set up a go-to scope? I could find them with
Submit Your Astro Tip! Astronomy Technology Today regularly features tips, tricks, and other novel solutions. To submit your tip, trick, or novel solution, email the following information: • A Microsoft Word document detailing your tip, trick or novel solution. • A hi-resolution digital image in jpeg format (if available). Please send your information to tips@astronomytechnologytoday.com
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planetarium software, but the dark sky looks very different. That's where the Celestron SkyScout comes in. I look through it, click a button, and it tells me the name of the star, planet, or deep sky object it's aimed at – like having a teacher at your side pointing you in the right direction. Its database is now up to 30,000 items, but you can’t see that many objects without a telescope. The SkyScout worked well, but it still took me lots of time to find the deep-space objects I wanted to see with the Dob. I tried a Sears digital level on the base of the dob, but it took time to look up RA and DEC points, and even then I was guessing at it. So I had the idea to save these steps by mounting the SkyScout directly to the LightBridge. But, it's made of steel and the SkyScout is very sensitive to ferrous metals. I did some testing and found a sweet spot to mount the SkyScout, and I am very pleased with the result. It’s not as good as a Sky Commander or Go-To mount – maybe < two degrees of accuracy – but close enough to put the target in the
view of a wide-field eyepiece. The sweet spot lets me keep the balance of the Dob, and with just a clamp-on setup, installation is easy. Just turn it on and push to go – no finding North or Setup Stars. I’m improving on the setup using all stainless parts, but you can get the idea, it’s the sweet spot that’s key. The photos tell the story. I’m about 12 inches from the edge of the secondary metal ring and the mount is about five inches high. I used a car-window camera mount made of stainless steel. I made a small slit in the shroud to go over the clamp, and with the camera mount it’s a fast setup. To get your setup to work, try not to use any ferrous metals, even screws. Find your sweet spot, turn the SkyScout on, and wait for the GPS fix. Adjust the camera mount to to center the SkyScout to the finder and move the scope slowly to let the electronics catch up. Don’t expect the unit to do much better than two degrees of accuracy, but do expect to spend more time at the eyepiece.
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