Amazon.com: Celestron NexStar 9 1/4 GPS Telescope (Telescope Only): Camera & Photo

Technical Details

Focal length of 2350mm
235mm (9 1/4-inch) diameter Schmidt-Cassegrain refractor
40,000 object database
16-Channel GPS
XLT coatings

Product Description

Amazon.com Review

Amazon.com Review Looking for an advanced telescope that combines great optics with equally good electronics and computerized control? If so, the Celestron NexStar 9.25 GPS is for you. It marries the proven NexStar GPS computer-driven telescope mount to the highly regarded Celestron 9.25-inch Schmidt-Cassegrain telescope to create one of the finest backyard telescopes in years.

The NexStar handset is your user-friendly, GPS-powered guide to more than 40,000 celestial objects.

The NexStar 9.25 GPS proves to be a real winner optically. The tell-all star test, where a star's image is examined and compared on both sides of focus, showed the test instrument's optics to be very good. There was little evidence of spherical aberration or other optical flaws that would hinder performance. This made for crisp and clear views of the planets and the Moon. Jupiter's belts were dazzling, with subtle colors and tenuous detail seen steadily, and the Great Red Spot was easy to make out. Saturn's rings were also very impressive. Deep-sky objects were no less appealing. For instance, M42, the Orion Nebula, was simply wonderful, with gossamer clouds curving in all sorts of intricate complexities. Open star clusters, such as M35 in Gemini and M41 in Canis Major, as well as globular clusters like M13 in Hercules and M22 in Sagittarius, were beautiful sights. Distant galaxies also showed a good amount of subtle detail. I could even make out hints of spiral structure in the face of the Whirlpool Galaxy, M51, as well as the famous black eye of M64 in Coma Berenices and the broad sombrero rim of M104 in Virgo.

The NexStar 9.25 GPS includes Celestron's exclusive Starbright XLT extra-high-transmission optical coatings on its front corrector plate as well as its primary and secondary mirrors. These coatings are designed to maximize brightness and contrast while minimizing light scatter.

Right out of the box, it quickly became apparent that this was no ordinary Schmidt-Cassegrain. For openers, the tube is not made of metal, but rather carbon fiber. Famous for its weight-to-strength ratio, carbon fiber's real strength is its thermal properties. In order for a telescope to perform optimally, the temperature of its optics must match that of the air. An hour or more may pass before the optics in a telescope brought outdoors from a warm house reach thermal equilibrium. A traditional metal tube--a great absorber of heat--only slows the process. Carbon fiber, on the other hand, absorbs heat less readily, shortening the cool-down process. The carbon-fiber tube also lessens focus shift as the telescope cools during the night, an especially important consideration in long-exposure astrophotos and CCD imaging.

I was also very impressed with the telescope's ability to locate itself. When turned on, it automatically links to the GPS system to determine the exact time and date and its location. Once that information has been determined and stored--a process that takes about a minute--the NexStar GPS automatically moves to two alignment stars, pausing each time to ask the user to center the star in its field of view. The initial alignment to the two reference stars may be off by 15 degrees or more because of the difference between the celestial and magnetic poles. The accuracy of the initial aiming can be greatly improved for future observation sessions by selecting the "Utilities" menu on the hand controller and choosing "Calibrate Compass" after successfully completing a GPS alignment. This will compensate for the difference between the poles, and the telescope will automatically retain that information for the future.

That done, the telescope is ready to hunt for buried treasure in the sky. The NexStar 9.25 GPS includes in its computerized database more than 40,000 objects, including those in the solar system as well as double stars, variable stars, and deep-sky objects from the Messier, NGC, IC, and many lesser-known catalogs. It will even take you on an automated tour if you prefer.

Also included are a 40mm Plossl eyepiece; a 1.25-inch star diagonal; a visual back adapter; a 9 x 50 straight-through finderscope; a sturdy, extendable steel tripod; and a hand controller; an AC adapter to power the built-in computer control; and a detailed instruction manual. All you need to add is a guidebook or two, such as my Star Watch, and a clear sky. --Phil Harrington, author of Star Ware

Pros

Great optics
Impressive GoTo accuracy
Carbon-fiber tube minimizes cool-down time
Ergonomic hand controller with convenient storage in fork arm

Cons

12-volt DC adapter must be purchased separately to run telescope off external battery
Wedge must be purchased separately for guided astrophotography
May be too heavy for some to carry and set up