The Celestron CGEM II 800 EDGEHD telescope puts unique new 8" aplanatic (free from coma and corrected for spherical aberration) EdgeHD high definition Schmidt optics on a precision Celestron CGEM II go-to German equatorial mount. The advanced EdgeHD optical design has a dual-element field flattener lens made from premium Schott optical glass in its central baffle tube that reduces off-axis coma and produces aberration-free images across awide 42mm image circle (as large as the diagonal of a 35mm negative or large format CCD chip and ideal for astrophotography).
As Sky & Telescope said in their Hot Product for 2010 citation for the EdgeHD optics, "the EdgeHD series represents the first major redesign of the Schmidt-Cassegrain optical system that Celestron introduced inthe 1960s. The addition of a two-element field flattener and coma corrector in the scope's main baffle tube produces pinpoint star images across the whole field of today's large-format CCD cameras. And the new mirror-support system reduces the image shift that was often the bane of the earlier Schmidt-Cassegrain telescopes."
In addition to reduced off-axis coma, the EdgeHD optical system delivers an astrograph-quality focal plane that is more than three times flatter than a standard Schmidt-Cassegrain telescope and dramatically flatter than other competing coma-free designs. Stars are smaller and more concentrated, creating brighter images and allowing you to see down to a fainter magnitude than other equally-sized telescopes. This guarantees you visibly sharp stars to the very edges of some of the largest CCD and DSLR chips available today.
Add Celestron's renowned Starbright XLT multicoatings on every optical surface, and the EdgeHD optic design gives you maximum light throughput across the widest possible visual and photographic spectrum. The CGEM II 800 EDGEHD's light grasp of almost 850 times that of even the sharpest dark-adapted eye can reveal to you star clusters, nebulas, planets, and galaxies in amazing visual and photographic detail. The Fastar-compatible optical tube allows imaging down to an incredibly-fast f/2 focal ratio using optional accessories.
The smooth and precise Celestron CGEM II go-to mount makes finding over 40,000 of those stars and objects easy and automatic. You spend more time looking at celestial objects, rather than looking for them. The CGEM II mount combines portability and premium-level performance with a payload capacity of 40 pounds. This makes for rock-steady imaging and visual observing with the light weight 8" Celestron EdgeHD optical system.
The sensible price of the CGEM II 800 EDGEHD with Starbright XLT coatings makes true astrographic-quality imaging and visual astronomy available at a reasonable price for almost everyone. Its light weight optical tube and easily assembled mount make it easy to set up and enjoy - either in your back yard or at a distant dark sky site. Its superb flat-field reduced-coma optics and very reasonable price for a full-featured computerized go-to mount make it a telescope that will make advanced backyard astronomer very happy for years tocome.
This Telescope's Optical System . . .
EdgeHD Schmidt-Cassegrain optical tube: 8" aperture (2032mm focal length f/10). Built-in dual-element field flattener lens in the central baffle tube. Guaranteed diffraction-limited optical performance, free from coma and corrected for spherical aberrations (aplanatic design). The optical design is a Sky & Telescope Hot Product for 2010. The 17" long aluminum optical tube weighs only 14 pounds and has a large handle on the rear cell, making it easy to transport and assemble the scope in the field.
StarBright XLT fully-multicoated optics: This high transmission/high reflectivity optical multicoatings package is applied to all optical surfaces. Starbright XLT coatings give you visibly higher light transmission for visually brighter deep space images and shorter exposure times during imaging. They also increase the contrast on subtle lunar, planetary, and nebula details when compared with a scope with ordinary coatings or multicoatings.
Tube vents: Two cooling vents located on the rear cell allow warm air to be released from behind the primary mirror when the scope is taken out for a night's observing or imaging. This shortens the amount of time needed for the optics to cool down to ambient air temperature for peak optical performance. Each vent has an integrated 60 micron micro-mesh filter guaranteed to let warm air out without letting dust in.
Fastar compatible: For the ultimate in wide-field catadioptric imaging, the EdgeHD optical tube is Fastar compatible to allow CCD imaging at a blazingly-fast f/2 focal ratio. An optional Fastar lens assembly lens replaces the telescope's removable secondary mirror (an exchange that takes only a few minutes). Your CCD camera is attached to the Fastar lens. This puts your camera at the f/2 position in the center of the Schmidt corrector lens at the front of the scope, rather than in its normal f/10 position at the Cassegrain focus at the rear of the scope.
Focusing: Focusing is accomplished by turning a knob at the rear of the scope body that moves the primary mirror fore and aft along a central baffle tube to adjust the focus. The Celestron focusing mechanism is supported by two pre-loaded ball bearings, minimizing the "mirror flop" typical of bushing focus mechanisms that causes image shift during critical focusing.
Mirror locks: Flexible tension clutches hold the mirror in place after correct focus is achieved for imaging and reduce image shift when rotating the tube around the mount (while moving past the zenith during astrophotography, for example). Unlike other designs that have only one locking knob located off to one side of the mirror, the Celestron system uses three locks equally spaced around the mirror to distribute the mirror locking force symmetrically. The focuser itself acts as one of the locks, while two flexible rods spaced 120° away in either direction act as the second and third locks. Controlled by variable tension knobs on the rear cell, these rods act in conjunction with the focuser to hold the mirror in place without putting any asymmetrical force or pressure on the mirror. This keeps the image centered in the eyepiece (or chip) no matter what the orientation of the optical tube.
Finderscope: 9 x 50mm straight-through achromatic design, with a wide 5.8° field of view, mounted in a spring-loaded easy-adjust quick release bracket.
Visual back: Removable 1.25" visual back holds visual accessories such as star diagonal, tele-extender, etc.
Star diagonal: 1.25" prism type.
Eyepiece: 1.25" 40mm Plössl (51x). The eyepiece field of view is 0.84 degrees, almost 70% larger than the full Moon.
This Telescope's Mount. . .
Heavy duty CGEM II computerized German equatorial mount: The CGEM II mount includes dual-axis slewing/tracking motors on each axis for go-to computer control. There are nine motor drive speeds: 0.5x and 1x sidereal for guiding; 4x, 8x, 16x, and 64x for centering; and 0.5°, 2°, and a fast 4° per second for slewing. Preset tracking rates include sidereal, solar, and lunar for precise tracking of celestial objects inside the solar system as well as out in deep space.
Powering the CGEM II 1100: The mount comes with a car battery cord to operate from the cigarette lighter plug of your car or from a rechargeable 12VDC battery pack. The 17 amp hour capacity Celestron Power Tank #4517V is recommended and will operate the scope all night long without danger of running out of power.
Polar alignment: To make a casual polar alignment for visual use quick and easy, there's a latitude scale with large ergonomically-friendly altitude and azimuth adjustment knobs. No polar alignment finderscope is available to aid in the precise polar alignment required for long exposure astrophotography, nor is any needed. A unique Celestron All-Star Polar Alignment program built into the NexStar hand control helps you do a very precise computerized polar alignment in mere minutes, using any bright star, even when Polaris is hidden by trees or buildings. The program works in both northern and southern hemispheres.
Adjustable height tripod: The tripod has 2"diameter stainless steel legs with a metal center leg brace for rigidity, for excellent vibration damping characteristics. The tripod also includes graduated markings on the tripod legs that will assist in quickly leveling the instrument. The center leg brace is drilled to form a convenient accessory tray that holds 1.25" and 2" eyepiece to keep them up out of the dew-soaked grass.
Mounting the scope: New for the CGEM II mount is a dual saddle plate. The saddle plate will now accept both the CGE/Losmandy wide dovetail plate as well as the AVX/Vixen style dovetail plate. The dovetail slot on the top of the mount holds the long dovetail slide bar mounted under the optical tube. This allows you to slide the optical tube fore and aft in the dovetail slot to quickly and precisely balance the optical tube in declination when you add or subtract accessories, eliminating the need for an extra counterweight to balance a camera or other accessories. Setup and takedown times are exceptionally fast, as a single large hand-tighten knob holds the optical tube in place. A second lock knob prevents the tube from sliding off the mount should the hand-tighten knob loosen. The oversized dovetail mounting platform assures secure vibration-free tube attachment.
Balancing the scope: The 17 pound counterweight is locked in place on the counterweight shaft with a single large hand-tighten knob. This makes it easy to rebalance the scope in right ascension if you add heavy photographic accessories.
NexStar computer hand control: The supplied NexStar computer hand control has a built-in database of more than 40,000 stars and objects that it can find and track for you. These include the complete RNGC, Messier, Caldwell, IC, and Abell catalogs; selected SAO stars; the planets, the Moon, and others. The custom database lists of all the most famous deep-sky objects by name and catalog number; the most beautiful double, triple and quadruple stars; variable stars; non-planetary solar systems objects; and asterisms.
The NexStar display: All of the database and scope operation information is displayed on a double line,16-character, liquid crystal display on the hand control. There are 19 fiberoptic backlit LED buttons to make it easy for you to control the computer without affecting your dark-adapted vision. The NexStar hand control provides a constant and easily-visible illuminated right ascension and declination readout of the scopes position on the sky. This provides much greater accuracy than conventional (and hard to see at night) manual setting circles for star-hopping or locating objects by their celestial coordinates alone, should you want to observe the old-fashioned way without using the computer to find objects for you.
Some NexStar features: New for the CGEM II mount, a USB 2.0 communication port on the hand control allows you to operate the telescope via a personal computer using a USB cable and NexRemote software CD-ROM. The hand control and motor control software is flash-upgradeable to allow you to download the latest product updates over the Internet to keep your CGEM II mount always at the cutting edge of technology. An autoguider port is located on the electronic pier for guided, but unattended, long exposure astrophotography.
Two-year warranty: All Celestron go-to telescopes have a two-year warranty.
