Celestron Advanced Series C8-SGT 203 x 2032mm Telescope
by Celestron

List Price: $2,455.95
Category: Digital Camera
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Digital Photo Product Details

• Mounted on the CG-5GT computerized EQ mount
• 40,000+ object database with 400 user-definable objects and expanded information on over 200 objects
• Double line, 16-character liquid crystal display (LCD) hand control with 19 fiber optic backlit LED buttons
• DC Servo motors with encoders on both axes
• Proven NexStar computer control technology

• AmazonBasics Universal Camera Case for Digital Cameras HF (Black)
• Corel PaintShop Photo Pro X3 [OLD VERSION]
• Corel Photo & Video Pro X3 Bundle [Old Version]
• AmazonBasics Camcorder/Camera Bag with Shoulder Strap (Black)
• Celestron Nexstar RS 232 PC Interface Cable

Description of Celestron Advanced Series C8-SGT 203 x 2032mm Telescope

The Celestron C8 S-GT is one such package. The latest of many C8 incarnations since it was first introduced in 1970, the C8 S-GT bears more than a passing resemblance to its predecessors. Like earlier models, the C8 S-GT is built around Celestron's 8-inch f/10 Schmidt-Cassegrain telescope assembly. Inside, an 8-inch primary mirror reflects light to a smaller secondary mirror at the top end of the tube. Light is then directed back through a central hole in the primary, and into the eyepiece. Focusing is done by turning a small knob on the tailstock of the instrument.

The C8 S-GT comes on the CG-5GT mount and tripod, which includes a NexStar onboard computer drive and hand controller. Once the mounting is initialized by aiming its polar axis roughly toward the celestial pole and calibrating the instrument with three alignment stars, a procedure that's well documented in the instruction manual, the telescope is ready to use.

The NexStar computerized goto system is powered with 12-volts DC for easy use in the field. Because of power requirements, however, Celestron does not include a dry-cell battery holder, as some DC-powered telescopes do. Instead, they include a 24-foot cord to plug into an automobile cigarette lighter or rechargeable battery, which makes much more sense. A 110-volt AC adapter is sold separately.

Testing the optical quality of the C8 S-GT revealed that my test telescope had a final wavefront error of about 1/4 wave, which is considered "diffraction limited." This means that the telescope will perform up to the limits of atmospheric conditions. In actual use, images of brighter objects, such as the planets, had a slight haze around them. Still, Saturn was certainly sharp enough to distinguish Cassini's Division as well as the planet's subtle equatorial belt, while Jupiter's banded atmosphere showed a good amount of detail. Double stars, such as Castor and Rigel, were easy to resolve, especially when I replaced the standard 25-mm Plössl (81x) with a shorter focal length eyepiece from my own collection.

The NexStar GoTo system performed very well night after night. At each stop, the target was either within or very near the field of the C8 S-GT's 25-mm eyepiece. Try as I might, I only managed to the CG-5GT mount into a mental tailspin once when I told it to find Polaris. It must have thought I had moved to Australia, as the telescope stopped nose down to the ground. After reinitializing the mount and selecting Polaris a second time, everything worked as it should.

Overall stability of the Advanced Series CG-5GT mount is much better than earlier CG-5s thanks to the sturdier tripod. A direct comparison between the new CG-5GT and my own, older CG-5 confirmed that vibration-dampening times have been almost cut in half with the new tripod. It's still a little too wobbly for long photographic time exposures through the telescope, but is quite acceptable for a visual instrument. It is also well suited for short exposures of the Moon and planets as well as piggyback-guided, wide-field exposures. --Phil Harrington, author of Star Ware and Star Watch

Pros:

• Reliable GoTo computer control
• Sturdy tripod and mount
• Good optics
• Well designed hand controller

• Mount not quite stable enough for long photographic exposures through the telescope

Catadioptric

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