Celestron SkyProdigy 6 SCT
David Hinds Ltd. — www.celestron.uk.com
Written: Summer/Autumn 2012

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It's sobering to recall that the world's first volume production computerised Schmidt-Cassegrain telescope (SCT), the Celestron CompuStar, appeared in 1985. Fast forward 27 years and Celestron continues to hold a veritable Olympian technological lead with the award-winning SkyProdigy — a line of robotic telescopes that automatically align themselves on the sky. This review focuses on the largest and most advanced instrument of the range, the SkyProdigy 6 SCT.

First impressions
The SkyProdigy 6 SCT arrives in a single box measuring some 76 x 75 x 38cm (30 x 30 x 15") and tipping the scales around 18kg (9.5kg of this being the 'scope, mount and tripod). Even a complete novice will have the instrument up and running in no time thanks to a profusely illustrated four-page quick set-up guide. In essence, assembly consists of attaching the mount to the tripod, sliding the optical tube's mounting bracket into the tube clamp, fitting the star pointer and installing 8 x D-size batteries into the separate battery pack (cells not included). If any further technical details need clarification then you can resort to the 32-page reference manual that covers the instrument's use and maintenance.

Celestron's technical data states that the payload limit of the SkyProdigy mount is 3.6kg (8 pounds), which means that the 6-inch SCT optical tube places the mount close to its operational limit. That said, the mount handles this load with aplomb and I never noticed flexure in the single fork design or the motors were placed under any strain. However, I do feel that the tripod is somewhat undersized and lightweight. When the legs are retracted the stability is good (induced vibrations on a hard standing died away in a couple of seconds), but the average eyepiece height is then 75cm (30") — too low to use unless I physically sat on a cushion on the ground. With the tripod legs fully extended the average eyepiece height becomes a far more useable 120cm (47") when standing, though induced vibrations take 4—5 seconds to disappear. Mid-range is comfortable for an adult from a seated position and offers the best stability compromise.

How does it work?
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Rather than using GPS and myriad sensors to model the telescope's position in space, each SkyProdigy couples a built-in CCD digital camera carefully aligned with the instrument to Celestron's computerised StarSense star pattern recognition system running on a built-in computer. Using a SkyProdigy is simplicity itself: set it up outside, apply power and press the Align button on the hand controller; within 5 minutes you can be observing! You don't need to know any alignment stars, or enter your latitude, longitude or time data (but it does possess a built-in clock and remembers this data between sessions if you do). If you wish to observe the Moon or planets in strong twilight when no stars are available to StarSense, then Celestron thoughtfully includes the Solar System Align feature from the NexStar and SLT mounts — this is a very well thought-out package. (Solar System Align is the only time you will use the star pointer; a SkyProdigy never normally needs a finder!)

How well does StarSense perform?
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I was initially sceptical that a completely automated alignment system could cope with the rigours of computerised star pattern recognition, partial cloud cover, light pollution, etc. — particulary in a country with such variable sky conditions as England. However, having been introduced to the SkyProdigy 130 for a recent magazine review in addition to this top-of-the-range 6 SCT, I can testify that the system works reliably, consistently and very well indeed! Just occasionally an auto alignment will fail if there are too few alignment stars, but repositioning the 'scope to avoid obstructions and restarting will usually result in a quick and accurate fix.

The lowest power (25mm) eyepiece of the SkyProdigy 6 SCT delivers a magnification of 60x and a true field of view of 0.8° (48 arcminutes), yet the system had no problems in routinely positioning any requested object within the eyepiece view — frequently within the centre third of the field of view! Sometimes the 'scope will not take the shortest route from one object to the next, but this is in order to prevent the cord from the power pack becoming entangled around the mount. Incidentally, Celestron's decision to use D-cells in the battery pack was a good one as it can provide enough power for a night's viewing (an optional dew shield being a wise investment).

Optical performance
It's gratifying to see such consistency in the optical quality of Celestron's Chinese-made 6-inch Schmidt-Cassegrain tube assemblies. The review model was every bit as good (if not slightly better) than those of my NexStar 6 SE review, so you can be assured that the SkyProdigy 6 SCT will deliver everything you can expect of an obstructed catadioptric system of this aperture. I always feel that a 6-inch 'scope hits a sweet spot in terms of performance vs. portability; there's sufficient aperture to see reveal structure in showcase deep-sky objects, while the Moon and bright planets will be seen in rich, awe-inspiring detail.

Even in the deep twilight of a high-latitude summer, the 'scope delivered images of globular cluster M13 that filled the centre of the 25mm eyepiece field with innumerable stars to averted vision; stars could be seen to the core with direct vision in the 9mm eyepiece. Albireo (beta Cygni), one of my all-time favourite double stars owing to the contrasting amber and blue components, appeared tack-sharp in the 9mm eyepiece, with a clear second diffraction ring around each component in moments of good seeing. The review 'scope's optics were smoothly polished with a high degree of spherical correction delivering views worthy of a Maksutov system.

Conclusions
Having seen so many fine telescopes over the years, I could get jaded about the hype generated by the 'next big thing' in telescope design and mount technology, but I felt genuine excitement about the time I spent using the SkyProdigy 6 SCT. Time and time again I found myself shaking my head in wonder that such opto-electronic wizardry is available, making the sky so accessible for absolute beginners, yet providing many advanced features to satisfy the experienced observer. If you have a patio or balcony, the instrument is manageable enough to leave permanently setup for an adult to carry outside in one piece, so that you can be ready to observe in literally five minutes (though the optics will need 30 mins. or more to settle down to ambient temperature for the best high-power views). Futhermore, the striking red and black livery and high-tech styling will make it a conversation piece in your living room!

Traditional experienced observers can be quick to be dismissive of high-end GoTo 'scopes like the SkyProdigy, saying that a novice benefits from learning a few naked eye alignment stars required by simpler (and cheaper) GoTo instruments in order for them to get familiar with the sky. These arguments have merit and I would be the first to advocate acquiring an in-depth knowledge of the sky (after all, that's what old-time observers like myself had to do), but the simple fact is that these days many people can only snatch 30 minutes from their busy lives to take a look at the wonders of the sky. A SkyProdigy will maximise that time for you, giving your family and friends a wonderful tool to explore the universe in fabulous detail, hopefully turning a fledgling interest into a consuming hobby. Unhesitatingly recommended.