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Starizona Hyperstar: Review after 17 Years of Imaging

The Elephant Trunk Nebula in IC 1396 imaged from a bright urban location with a total exposure of 5 hours 16 minutes using a ASI294MC Pro camera and a Triad Ultra filter on a C 14 Hyperstar. Credit: Robert Reeves

In the 1990s, Celestron teamed with SBIG to create the Fastar astrophotography system which allowed the replacement of the traditional Schmidt-Cassegrain secondary mirror with a small CCD camera, creating an ultra-fast F/2 astrograph. While the Fastar CCD system was discontinued in 2000, all C-6 through C-14 telescopes still feature “Fastar-compatible” removable secondary mirrors, as indicated by the colorful “Fastar” logo on the face of the secondary holder.

 

The Hyperstar lens assembly features a field corrector that spans the width of the host telescope’s secondary mirror support. Credit: Robert Reeves

In 2005, Dean Koenig and his associates at Starizona in Tucson, Arizona, created the Hyperstar photographic system. Unlike the original narrow-field Celestron Fastar system, the Hyperstar incorporates a wide field flattener to allow any Fastar-compatible SCT to act like the Celestron Schmidt camera that was revered in the film photography era. The resulting astrograph F/ratio depends on the telescope model used, varying from F/1.9 to F/2.3.

Once the telescope’s secondary mirror is removed, the Hyperstar lens assembly screws onto the threaded secondary mirror support. Credit: Robert Reeves

The Hyperstar system was initially offered for both Meade 10- and 14-ich SCTs, as well as Celestron telescopes, but the Meade option is no longer offered due to low demand. Starizona offers a $250 conversion kit to allow early model non-Fastar C-8 telescopes to accept the Hyperstar. Today, Version 4 of the Hyperstar is a coveted accessory that bridges the gap between wide-field camera lens astrophotography and high-resolution prime focus photography.

The larger Hyperstar camera adapters have two-inch filter threads. Credit: Robert Reeves

A needless concern is whether the SCT corrector plate can adequately support the weight of the Hyperstar and camera assembly. The heaviest Hyperstar lens is the 3.1-pound C-14 model. When installed, the lens assembly projects the mass of the camera about six inches out from the corrector. This applies torque to the corrector equal to the camera weight times the length of the Hyperstar, plus the Hyperstar’s own weight. Celestron performed corrector plate load tests to verify the safety of the Hyperstar system and found the failure weight of a mass suspended at Hyperstar distance from the C-14 corrector was 70 pounds. Thus, any camera system installed on the Hyperstar will have a weight safety factor of between five to 10 times the mass of the camera.

The collimation of a Hyperstar has also been the source of angst among astrophotographers, but the process is little different than ordinary Schmidt-Cassegrain collimation when using the Hotech Advanced CT laser collimator and the accessory Hotech Hyperstar reflector mirror. An “eyeball” collimation process can also be done by following the steps outlined in the excellent document “The Amazing HyperStar: A Guide to Optimize Performance”, available online at:

https://www.cloudynights.com/articles/cat/articles/the-amazing-hyperstar-a-guide-to-optimize-perf-r3013

Starizona provides camera-specific Hyperstar adapters for all popular camera types that will have the proper DSLR lens mount or T-threads. The adapter automatically spaces the camera at the proper back focus distance. Camera adapters for the C-6 only accept 1-¼-inch threaded filters for sensor sizes no larger than 11mm, while the C-8 and larger adapters accept 2-inch threaded filters. A Starizona filter slider is also available for the larger Hyperstars to allow changing filters without dismounting the camera. The proper camera-specific filter slider adapter is also needed to maintain correct back focus. Unfortunately, the filter slider will not work with mirrored DSLRs or with the smaller C-6 and C-8 Hyperstars.

The combined mass of they Hyperstar and camera assembly are well within the safe weight capacity of the host telescope’s corrector plate. Credit: Robert Reeves

The Hyperstar optical system is best matched with an APS-C sized sensor. Full-frame DSLRs will show significant vignetting due to image clipping by the DSLR mirror box. Mirrorless cameras are less prone to vignetting, and dedicated CMOS and CCD astrocameras with the sensor mounted near the front of the camera work best. I have no uncorrectable vignetting issues with my ASI294MC Pro on a C-14 Hyperstar.

The front-mounted camera shadow footprint has minimal effect on the final image if the camera body does not significantly exceed the diameter of the Hyperstar lens itself. Normal-sized DSLR bodies will work on C-9.25 and larger scopes. However, a DSLR will block too much of the aperture with a C-6 and C-8. The smaller model Hyperstars will need smaller cylindrical cameras like QHY and ZWO models to prevent occulting too much of the telescope’s aperture.

A split Bhatinov mask allows accurate focusing of a Hyperstar within seconds. Credit: Robert Reeves

Focusing the Hyperstar is performed using the telescope’s standard focus knob. The Hyperstar’s fast F/ratio narrow zone of focus is easy to adjust with a split Bahtinov mask such as the one available from 3-D printing sources like Photon Express (https://jwbozeman.com). Hinged split Bhatinov masks are preferred to eliminate interference by the camera’s power and USB cables. Most Celestron SCTs have temperature-sensitive aluminum tubes and the Hyperstar will need refocusing if the temperature drops as the night progresses.

Since the Hyperstar lens assembly replaces the secondary mirror, the Hyperstar is not a visual instrument. However, the optical power of the Hyperstar is demonstrated when an ultra-sensitive camera like the Sony a7 is installed on a large SCT equipped with Hyperstar. While viewing with the camera’s LCD viewfinder, the target image can often be seen behind the viewer even with it partially occulted by the viewer’s head.

A one-hour exposure reveals expanding gas shells surrounding M-27, the Dumbbell Nebula in this urban location exposure taken with an ASI294MC Pro camera and Triad Ultra filter on a C 14 Hyperstar. Credit: Robert Reeves

Exposures times with the Hyperstar are surprisingly short and can reach the sky fog limit in seconds unless contrast-enhancing or light pollution filters are used. Exposures that would theoretically take 25 minutes at the telescope’s traditional F/10 configuration take only 60 seconds with the F/2 Hyperstar. The fast Hyperstar optics even allow imaging targets with an alt-az mount. A stack of 20-second sub-exposures will reduce the effect of field rotation and allow stunning images of brighter targets.

M-20, the Trifid Nebula, imaged from a deep urban location with an ASI294MC Pro camera and a Triad Ultra filter on a C 14 Hyperstar. Total exposure time was one hour. Credit: Robert Reeves

The fast Hyperstar imaging system is traditionally regarded as a dark sky instrument but combined with aggressive light pollution filters such as the Radian Triad Ultra F3.0 filter (also reviewed in AstroGear Today), the Hyperstar is a powerful and very viable urban deep sky astrograph. I do all my Hyperstar deep-sky imaging from within a city of two million. The results shown on these pages speak for themselves. A properly filtered Hyperstar is a stunning urban astrophoto tool.

NGC-6979, Pickering’s Triangle, with a total exposure time of 2 hours and 18 minutes using an ASI294MC Pro camera and Triad Ultra filter on a C 14 Hyperstar from a deep urban location. Credit: Robert Reeves

To conclude, what’s not to love about the Hyperstar? Its short focal length simplifies autoguiding, and with proper filtration it allows backyard urban astrophotography that would have been impossible just a few years ago. The Hyperstar lens assembly would be a valued astrophotography accessory for all Celestron SCT owners.

Plus: The Hyperstar lens converts a Fastar-compatible telescope into a powerful Schmidt camera-like astrograph.

Minus: Short focal lengths aren’t suited for smaller deep sky targets.

Website: www.starizona.com

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About Robert Reeves

Robert Reeves has been exploring the Moon since 1958 and took his first lunar photograph in 1959. He began telescopic astronomy with a four-inch Criterion Dynascope. Today, Reeves uses a Celestron 11 Edge HD, a Sky-Watcher 180mm Maksutov, and a Sky-Watcher 20-inch Stargate Dobsonian for lunar photography, and a Celestron C-14 with a Hyperstar for deep-sky photography from his Perspective Observatory located in central Texas. Robert has published over 250 magazine articles and 200 newspaper columns about astronomy and has authored several books, including The Superpower Space Race, The Conquest of Space (co-authored with Fritz Bronner), Wide-Field Astrophotography, Introduction to Digital Astrophophotography and, most recently, Introduction to Webcam Astrophotography. Although Robert Reeves is an accomplished deep sky astrophotographer, his current passion is re-popularizing the Moon with the public and the amateur astronomy community. He enjoys speaking to astronomy conventions and spreading his passion for the Moon.

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