Celestron Nexstar 8GPS Telescope (Telescope only)
by Celestron

List Price: $4,098.99
Category: Digital Camera
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Digital Photo Product Details

• Focal length of 2032mm
• 203mm (8-inch) diameter Schmidt-Cassegrain refractor
• Observe immediately with the computerized auto align feature
• Automatic slewing to over 18,000 celestial objects
• Common sense menu descriptions

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Description of Celestron Nexstar 8GPS Telescope (Telescope only)

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

The telescope and fork mount assembly come with a variety of standard accessories, including a 40-mm Plössl eyepiece, a 1.25-inch star diagonal, a visual back adapter, a 9x50 straight-through finderscope, a hand controller, and an AC adapter to power the built-in computer control.

Right out of the box, it quickly becomes apparent that this is no ordinary Schmidt-Cassegrain. For openers, the tube is not made of metal, but rather carbon fiber. Carbon fiber has been used in recent years for everything from sailboats to high-end bicycles, and is famous for its weight-to-strength ratio. But for telescopes the real value is its thermal properties. In order for a telescope to perform optimally, the temperature of its optics must match that of the outside 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, does not absorb heat as readily, shortening up the cool-down process. The carbon-fiber tube also lessens focus shift as the telescope cools during the night, an important consideration for long-exposure astrophotos and CCD imaging.

Of all the C8s that I have viewed through recently, including several NexStar 8 GPSs, all have produced sharp images of the Moon and naked-eye planets. Jupiter, for instance, reveald some very sharp detail in the Jovian clouds, while Saturn's rings, including Cassini's Division and the elusive C ring, were clearly resolved.

Deep-sky objects can also be viewed well with the NexStar 8 GPS. For example, the four stars in the Trapezium quadruple star system buried inside the Orion Nebula were easily resolved. Under steady seeing conditions, I could also just barely make out one of the two fainter "E" and "F" stars set amongst the brighter four, which are a good test for an 8-inch.

Star testing a NexStar 8 GPS, I found that the optics were top quality. Images both inside and outside of focus were identical (comparing the two is what a star test is), and nearly textbook perfect. I could detect only the slightest hint of spherical aberration. Astigmatism and other telltale optical imperfections were imperceptible.

Throughout these travels, I found images to be sharp and contrasty, a testimony to Celestron optics as well as their excellent coatings. Optical collimation was also very close to perfect right out of the box, indicative of Celestron's product inspection and packing ability. Corrections are easily made by turning one or more of the adjustment screws on the secondary-mirror assembly. The instruction manual that comes with the telescope includes a very good description of this procedure, as well as other important topics, such as telescope set-up and care, use of the hand controller, and even a primer on observing the sky and astrophotography.

It must be noted, though, that the 40-mm Plössl eyepiece that comes with the telescope is mediocre at best, and should be replaced with better eyepieces as soon as funds permit. At a minimum, I would recommend a 32-mm Plössl eyepiece for low-power viewing, a 17- to 20-mm eyepiece for medium power, and a 9- to 12mm eyepiece for high-power views. You should also consider premium eyepieces, such as the Tele Vue 11mm Nagler Type 6 as well either their 8mm Radian or 9mm Nagler Type 6 All will show the full potential of the NexStar 8 GPS, and will last a lifetime if properly cared for. Even if money is tight after the telescope purchase, try to expand your eyepiece collection with some budget-priced Plössl eyepieces.

When it comes to an advanced instrument outfitted with all the bells and whistles, the NexStar 8 GPS is a leader in the field thanks to its easy set-up, ergonomically friendly design, crisp optics, and intelligent options. --Phil Harrington, author of Star Ware

Pros:

• Excellent optics
• Starbright XLT coatings increase image contrast and sharpness
• Carbon-fiber tube

• Mediocre 40-mm eyepiece

Catadioptrics     This is a catadioptric telescope. Catadioptrics use an ingenious combination of mirrors and lenses to "fold" the light path into a remarkably compact tube. This type of design--which includes Schmidt-Cassegrain and Maksutov-Cassegrain telescopes--offers good value even while it scores high on the techno-geek meter.     Read more about different telescope designs in our buying guide

The NexStar GPS Series 8GPS Specifications:

• 8" (203.2mm) Schmidt-Cassegrain Optical Design
• 2032mm Focal Length, f/10
• StarBright Multi-Coatings
• Dual Fork Arm
• Carbon Fiber Optical Tube
• Fastar Compatible for f/2 CCD Imaging
• Double line, 16 character Liquid Crystal Display; 19 fiber optic backlit Computer Hand Control
• RS-232 communication port on hand control
• Auxiliary Port and Autoguide Port on Drive Base
• 40,000+ object database
• 16 channel GPS Receiver
• Fork Tine and Optical Tube Weight ? 42 lb.

• 1-1/4" 40mm Eyepieces (51x)
• 1-1/4" Star Diagonal
• 9x50 Finderscope and Mounting Bracket
• 1-1/4" Visual Back
• AC Adapter (car battery adapter is included with some models)
• NexRemote Telescope Control Software

Often, it is tempting to look at the Moon when it is full. At this time, the face we see is fully illuminated and its light can be overpowering. In addition, little or no contrast can be seen during this phase. One of the best times to observe the Moon is during its partial phases (around the time of first or third quarter). Long shadows reveal a great amount of detail on the lunar surface. At low power you will be able to see most of the lunar disk at one time. The optional Reducer/Corrector lens allows for breath-taking views of the entire lunar disk when used with a low power eyepiece. Change to higher power (magnification) to focus in on a smaller area. Choose the lunar tracking rate from the NexStar's MENU tracking rate options to keep the moon centered in the eyepiece even at high magnifications.

Observing the Planets
Other fascinating targets include the five naked-eye planets. You can see Venus go through its lunar-like phases. Mars can reveal a host of surface detail and one, if not both, of its polar caps. You will be able to see the cloud belts of Jupiter and the great Red Spot (if it is visible at the time you are observing). In addition, you will also be able to see the moons of Jupiter as they orbit the giant planet. Saturn, with its beautiful rings, is easily visible at moderate power. Remember that atmospheric conditions are usually the limiting factor on how much planetary detail will be visible. So avoid observing the planets when they are low on the horizon or when they are directly over a source of radiating heat, such as a rooftop or chimney.

The Nuts and Bolts:

Control Panel Focus Knob Star Diagonal Eyepiece Finderscope Finderscope Adjustment Screw Optical Tube Schmidt Corrector Lens Hand Control Fork Arm Carrying Handle Tripod (not included)

Catadioptric

• Camera & Photo > Binoculars, Telescopes & Optics > Telescopes > Catadioptric