The Celestron CGEM II800 EDGEHD telescope puts unique new 8” aplanatic (free from coma and correctedfor spherical aberration)EdgeHD high definition Schmidt optics on aprecision Celestron CGEM II go-to Germanequatorial mount. The advanced EdgeHD optical design has a dual-element fieldflattener lens made from premium Schott optical glass in its central baffletube 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 largeformat CCD chip and ideal for astrophotography).
As Sky & Telescope said in their Hot Product for 2010citation for the EdgeHD optics, “the EdgeHD series represents the first majorredesign of the Schmidt-Cassegrain optical system that Celestron introduced inthe 1960s. The addition of a two-element field flattener and coma corrector inthe scope’s main baffle tube produces pinpoint star images across the wholefield of today's large-format CCD cameras. And the new mirror-support systemreduces the image shift that was often the bane of the earlierSchmidt-Cassegrain telescopes."
In addition to reduced off-axis coma, the EdgeHD opticalsystem delivers an astrograph-quality focal plane that is more than three timesflatter than a standard Schmidt-Cassegrain telescope and dramatically flatterthan other competing coma-free designs. Stars are smaller and moreconcentrated, creating brighter images and allowing you to see down to afainter magnitude than other equally-sized telescopes. This guarantees youvisibly sharp stars to the very edges of some of the largest CCD and DSLR chipsavailable today.
Add Celestron’s renowned Starbright XLT multicoatings on every optical surface,and the EdgeHD optic design gives you maximum light throughputacross the widest possible visual and photographic spectrum. The CGEM II 800EDGEHD’s light grasp of almost 850 times that of even the sharpest dark-adaptedeye can reveal to you star clusters, nebulas, planets, and galaxies in amazingvisual and photographic detail. The Fastar-compatible optical tube allowsimaging 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 thosestars and objects easy and automatic. You spend more time looking at celestialobjects, rather than looking for them. The CGEM II mount combines portability and premium-levelperformance with a payload capacity of 40 pounds. This makes for rock-steadyimaging and visual observing with the light weight 8” Celestron EdgeHD opticalsystem.
The sensible price of the CGEM II 800 EDGEHD with Starbright XLT coatings makestrue astrographic-quality imaging and visual astronomy available at areasonable price for almost everyone. Its light weight optical tube and easilyassembled mount make it easy to set up and enjoy – either in your back yard orat a distant dark sky site. Its superb flat-field reduced-coma optics and veryreasonable price for afull-featured computerized go-to mount make it atelescope that willmake advanced backyard astronomer very happy for years tocome.
This Telescope’sOptical System . . .
·EdgeHD Schmidt-Cassegrain optical tube: 8” aperture(2032mm focal length f/10). Built-in dual-element field flattener lens in thecentral baffle tube. Guaranteed diffraction-limited optical performance, freefrom coma and corrected for spherical aberrations (aplanatic design). Theoptical design is a Sky & Telescope Hot Product for 2010. The 17” longaluminum optical tube weighs only 14 pounds and has a large handle on the rearcell, making it easy to transport and assemble the scope in the field.
·Starbright XLT fully-multicoated optics: This hightransmission/high reflectivity optical multicoatings package is applied to alloptical surfaces. Starbright XLT coatings give you visibly higher lighttransmission for visually brighter deep space images and shorter exposure timesduring imaging. They also increase the contrast on subtle lunar, planetary, andnebula details when compared with a scope with ordinary coatings ormulticoatings.
·Tube vents: Two cooling vents located on therear cell allow warm air to be released from behind the primary mirror when thescope is taken out for a night’s observing or imaging. This shortens the amountof time needed for the optics to cool down to ambient air temperature for peakoptical performance. Each vent has an integrated 60 micron micro-mesh filterguaranteed to let warm air out without letting dust in.
·Fastar compatible: For the ultimatein wide-field catadioptric imaging, the EdgeHD optical tube is Fastarcompatible to allow CCD imaging at a blazingly-fast f/2 focal ratio. Anoptional Fastar lens assembly lens replaces the telescope’s removable secondarymirror (an exchange that takes only a few minutes). Your CCD camera is attachedto the Fastar lens. This puts your camera at the f/2 position in the center ofthe Schmidt corrector lens at the front of the scope, rather than in its normalf/10 position at the Cassegrain focus at the rear of the scope.
Using the Fastar system and a sub-$1500 Orion Star Shoot Deep Space Imager ProCCD camera, the 8" CGEM II 800 EDGEHD will record a wide 194 x 129 arcminute field – a long axis over six times the diameter of the full Moon, animmense field for a scope of this size. To assure repeatability when you switchbetween Fastar and conventional imaging, the scope’s optical tube isopto-mechanically aligned on a laser bench during manufacture so that allcomponents are axially symmetric in any configuration.
·Focusing: Focusing is accomplished by turninga knob at the rear of the scope body that moves the primary mirror fore and aftalong a central baffle tube to adjust the focus. The Celestron focusingmechanism is supported by two pre-loaded ball bearings, minimizing the “mirrorflop” typical of bushing focus mechanisms that causes image shift duringcritical focusing.
·Mirror locks: Flexible tension clutches hold themirror in place after correct focus is achieved for imaging and reduce imageshift when rotating the tube around the mount (while moving past the zenithduring astrophotography, for example). Unlike other designs that have only onelocking knob located off to one side of the mirror, the Celestron system usesthree locks equally spaced around the mirror to distribute the mirror lockingforce symmetrically. The focuser itself acts as one of the locks, while twoflexible rods spaced 120° away in either direction act as the second and thirdlocks. Controlled by variable tension knobs on the rear cell, these rods act inconjunction with the focuser to hold the mirror in place without putting anyasymmetrical force or pressure on the mirror. This keeps the image centered inthe eyepiece (or chip) no matter what the orientation of the optical tube.
·Finderscope: 9 x 50mm straight-through achromaticdesign, with a wide 5.8° field of view, mounted in a spring-loaded easy-adjustquick release bracket.
·Visual back: Removable 1.25” visual back holdsvisual accessories such as star diagonal, tele-extender, etc.
·Star diagonal: 1.25” prism type.
·Eyepiece: 1.25” 40mm Plössl (51x). Theeyepiece field of view is 0.84 degrees, almost 70% larger than the full Moon.
This Telescope’s Mount. . .
·Heavyduty CGEM II computerized German equatorial mount: The CGEM II mount includes dual-axisslewing/tracking motors on each axis for go-to computer control. There are ninemotor drive speeds: 0.5x and 1x sidereal for guiding; 4x, 8x, 16x, and 64x forcentering; and 0.5°, 2°, and a fast 4° per second for slewing. Preset trackingrates include sidereal, solar, and lunar for precise tracking of celestialobjects inside the solar system as well as out in deep space.
·Poweringthe CGEM II 1100: Themount comes with a car battery cord to operate from the cigarette lighter plugof your car or from a rechargeable 12VDC battery pack. The 17 amp hour capacityCelestron Power Tank #4517V is recommended and will operate the scope all nightlong without danger of running out of power.
·Polaralignment: To make a casual polaralignment for visual use quick and easy, there’s a latitude scale with largeergonomically-friendly altitude and azimuth adjustment knobs. No polaralignment finderscope is available to aid in the precise polar alignmentrequired for long exposure astrophotography, nor is any needed. A uniqueCelestron All-Star Polar Alignment program built into theNexStar hand control helps you do a very precise computerized polar alignmentin mere minutes, using any bright star, even when Polaris is hidden by trees orbuildings. The program works in both northern and southern hemispheres.
·Adjustableheight tripod: The tripod has 2”diameter stainless steel legs with a metal center leg brace for rigidity, for excellentvibration damping characteristics. The tripod also includes graduated markingson the tripod legs that will assist in quickly leveling the instrument. The center leg brace is drilled to form aconvenient accessory tray that holds 1.25” and 2” eyepiece to keep them up outof the dew-soaked grass.
·Mountingthe scope: New for the CGEM IImount is a dual saddle plate. The saddleplate will now accept both the CGE/Losmandy wide dovetail plate as well as the AVX/Vixenstyle dovetail plate. The dovetail sloton the top of the mount holds the long dovetail slide bar mounted under theoptical tube. This allows you to slide the optical tube fore and aft in thedovetail slot to quickly and precisely balance the optical tube in declinationwhen you add or subtract accessories, eliminating the need for an extracounterweight to balance a camera or other accessories. Setup and takedowntimes are exceptionally fast, as a single large hand-tighten knob holds theoptical tube in place. A second lock knob prevents the tube from sliding offthe mount should the hand-tighten knob loosen. The oversized dovetail mountingplatform assures secure vibration-free tube attachment.
·Balancingthe scope: The two sliding 17pound counterweights are locked in place on the counterweight shaft with asingle large hand-tighten knob each. This makes it easy to rebalance the scopein right ascension if you add heavy photographic accessories.
· NexStar computer hand control: The supplied NexStar computer hand control hasa built-in database of more than 40,000 stars and objects that it can find andtrack for you. These include the complete RNGC, Messier, Caldwell, IC, andAbell catalogs; selected SAO stars; the planets, the Moon, and others. Thecustom database lists of all the most famous deep-sky objects by name andcatalog number; the most beautiful double, triple and quadruple stars; variablestars; non-planetary solar systems objects; and asterisms.
·TheNexStar display: Allof 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 computerwithout affecting your dark-adapted vision. The NexStar hand control provides aconstant and easily-visible illuminated right ascension and declination readoutof the scopes position on the sky. This provides much greater accuracy thanconventional (and hard to see at night) manual setting circles for star-hoppingor locating objects by their celestial coordinates alone, should you want toobserve the old-fashioned way without using the computer to find objects for you.
·SomeNexStar features: New for the CGEM II mount, a USB 2.0 communication port on the hand controlallows you to operate the telescope via a personal computer using a USB cableand NexRemote software CD-ROM. The hand control and motor control software isflash-upgradeable to allow you to download the latest product updates over theInternet to keep your CGEM II mount always at the cutting edge of technology.An autoguider port is located on the electronic pier for guided, butunattended, long exposure astrophotography.
·Aligningon the sky: Five differentalignment methods are built into the NexStar computer – 2-star align, quickalign, 1-star align, last alignment, and solar align – allowing you to choose alevel of computer accuracy in automatically finding objects with which you arecomfortable. Alignment is easily accomplished in only a few short minutes. Youcan be observing in less than 15 minutes after you first take the scopeoutdoors. There’s even a new and unique “All-Star” software-assisted alignmentof the mount’s polar axis using a single bright star that will have you readyfor imaging before it’s even dark enough to see the North Star.
· Two-year warranty: All Celestron go-to telescopes have a two-yearwarranty, double that of competitive go-to scopes.