Celestron CGX 800 RASA 8" Telescope

• Flat field free of optical aberrations like field curvature, coma, astigmatism and chromatic aberration across an entire APS-C sensor.
• Unlike the larger RASAs that work with DSLR and large CCD cameras, the 8” model was designed with color astronomical CMOS cameras, smaller CCD cameras, and mirrorless cameras in mind. The telescope does not work with standard DSLR cameras.
• NEW Ultra-Stable Focus System – six precision sealed ball bearings virtually eliminate image shift.
• Integrated air cooling system –12V DC MagLev fan reduces cooldown time and provides optimal air flow while filtering out dust.
• Internal filter mount – seamlessly accommodates a Light Pollution Imaging Filter into the optical path.
• Performs over a wider spectral range than most telescopes, from 390-800 nm, so more of the light passing through the astrograph is in sharp focus.
• The CGX, with its 55 lb. load capacity, is Celestron’s most innovative, state-of-the art, computerized equatorial mount to date, and provides a very sturdy and rigid platform for the fully-loaded RASA 8.
• The drive system utilizes low cog DC Servo motors with integrated optical encoders, belt and pulley motor connection, spring-loaded steel worm gears supported by precision sealed bearings, and brass worm wheels for smooth, accurate slewing and tracking performance with little backlash.
• Fully remote imaging capable, with optical limit switches, home sensors, through-mount cabling, and hard stops.
• Included Celestron PWI software allows direct computer control via USB 2.0 connection.
• Proven NexStar+ computerized telescope control technology supports functions to address imagers’ needs, such as All-Star Polar Alignment, Permanent Periodic Error Correction (PPEC), and adjustable tracking through meridian.

This Celestron 8" f/2 Rowe-Ackermann Schmidt Astrograph (RASA) optical tube has:

Very fast 8" f/2 Rowe-Ackermann Schmidt optics 
StarBright XLT optical multicoatings for the highest possible light transmission
MagLev DC cooling fan and cooling vents 
Built-in corrector lens
Mirror locks
42mm T-thread and C Thread camera adapters
CGE (Losmandy-style "D-plate") dovetails 
2-year warranty

"I don't get it. What do you look through?"

This might be the most common question people ask when you unpack your new Celestron Rowe-Ackermann Schmidt Astrograph (RASA). It's not only missing something that comes with virtually every telescope ever produced . . . an eyepiece . . . it doesn't even have a place to put an eyepiece. That's because the 400mm focal length f/2 Celestron 8" RASA is strictly a deep space imaging scope and cannot be used visually.

But what an imaging scope! It has a 22mm image circle that can handle CMOS cameras, smaller CCD cameras, and mirrorless cameras.  The telescope does not work with standard DSLR cameras. It provides a proven Schmidt corrector optical system with a built-in corrector lens that keeps the images free of coma, field curvature, and false color. The optical quality and spot size across the entire image circle are unprecedented for an astrograph in this price range - or even that of a much more expensive instrument.

Its fast, wide field, f/2 optics give you two huge advantages over traditional f/10 catadioptric imaging scopes (even those using an optional f/6.3 or f/7 focal reducer). Those advantages? Better apparent tracking due to the image scale, plus shorter exposure times due to the speed of the optics. That means you can create better-looking deep space images in a fraction of the time it used to take, even without using an autoguider.

The Celestron RASA concept was to modernize the Celestron Schmidt camera, an instrument that had a loyal following, as its very fast focal ratio allowed amateur astrophotographers to produce wide field deep space images in the 1970s. Schmidt cameras could produce great images, but they wre and imaging scope only a really hard-core astrophotographer could love.

Those Schmidt cameras used a single frame of 35mm film, cut from a roll of film. You flexed the chip of film in total darkness (being careful not to touch the emulsion side) to fit snugly into a curved holder that matched the camera's curved focal plane, then loaded it into the camera by feel inside a black cloth bag to avoid image-spoiling stray light. You manually guided your scope during the entire exposure, keeping your eye glued to the crosshairs of an illuminated reticle eyepiece so your stars wouldn't turn into elongated squiggles. Finally, after a sometimes multiple hour single exposure, you tediously processed the small chip of film in your own darkroom before you could even begin to see if you had captured a usable image.

No more. Telescope mount drive accuracy has improved tremendously, electronic eyeballs have taken over guiding, and fast digital photography has taken the place of slow 35mm film.

Today's CCD camera can have sensors as large, if not larger, than film. To compensate for the new large sensors Celestron had to push the boundaries of the Schmidt camera design and make an entirely new type of instrument. The Celestron Rowe-Ackermann Schmidt Astrograph has provided that advance in the performance of deep space imaging scopes. With it, today's amateur astrophotographers can produce results rivaling that of the best professional observatory photos of only a few short years ago.

As with most advances in optics, the Celestron Rowe-Ackermann Schmidt Astrograph was designed not by committee, but by two dedicated optical experts who believed things could be done better - Dave Rowe and Mark Ackermann.

Dave Rowe - amateur astronomer, telescope maker, and optical designer - studied astronomy and astrophysics at Caltech, has published more than 50 papers, and holds 15 patents. Rowe has designed and fabricated many telescopes for Celestron and PlaneWave Instruments, including PlaneWave's corrected Dall-Kirkham and CDK700 telescope. He also worked closely with Celestron engineers in the development of the unique StarSense technology.

Mark Ackermann - amateur astronomer and experienced optical designer - earned a BS in mathematics and physics from the United States Air Force Academy, an MS in solid state physics, and a PhD in nonlinear optics from the University of New Mexico. He has published dozens of papers on optical telescope design and holds six US patents related to optical systems.

Engineered as a complete astroimaging system, every component of the Celestron Rowe-Ackermann Schmidt Astrograph is optimized for peak performance with CMOS, smaller CCD camers, and mirrorless cameras. Every component of the system has been designed to work together seamlessly, right down to the thickness of the glass used in the scope's fully-multicoated optical window.

Some of the advanced features of the Celestron 8" RASA includes mirror locks hold your precise focus. A quiet high-output 12V internal MagLev fan on the rear cell reduces cooldown time and provides optimal airflow through the dust filtered 24.7" long optical tube. Naturally, industry leading StarBright XLT optical multicoatings are standard equipment for the highest possible light throughput. A Losmandy-style "D-plate" dovetail is standard. The back focus with the included camera adapters is 25mm.

The Celestron #93614 RASA LPR (Imaging Filter is highly recommended with the RASA. The scope's incredibly fast f/2 focal ratio gathers so much light so quickly that even modest amounts of sky glow at a dark sky site can brighten the sky background and reduce the contrast in your images. In light-polluted city and suburban locations, the RASA Light Pollution Reduction (LPR) Imaging Filter is a must.

The CGX mount head contains dual-axis slewing/tracking motors on each axis for go-to computer control. This is where the real upgrades start.The mount uses spring-loaded worm gears with belt drives. The belt drives offer smooth, quiet operation, with precision slewing and tracking. The motor armatures are skewed to minimize cogging for precise jitter-free low speed tracking. The motor drives and their wiring are all internal, keeping them snag-free and free from dust and debris.

Redesigned electronics deliver constant regulated power to the motors, making them capable of driving the telescope even when the mount is not perfectly balanced. This allows the CGX to have the payload capacity of much larger mounts without sacrificing smooth tracking motion and pointing accuracy across the entire sky. For cutting edge mount control, the CGX supports Celestron's optional SkyPortal WiFi that lets you control the CGX from your smart devices. For automatic sky alignment, you can add Celestron's optional StarSense AutoAlign.

The mount requires a minimum 3.5 amp 12 VDC power supply to operate. The maximum 3.5 amp power draw happens only briefly when accelerating to the high speed slewing mode from a standing start, or decelerating from the high speed mode when approaching a computer-chosen object. Normal power draw with a well-balanced payload is generally less than half the maximum draw.

The mount comes with a car battery cord to operate from the cigarette lighter plug of your car or from a rechargeable 12V battery pack. The 17 amp hour capacity Celestron Power Tank #4517V is recommended and will operate the mount all night long without danger of running out of power. An optional Celestron #2338PRO 5 amp AC adapter will let you power the CGX all night long from household AC.

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. It works in both northern and southern hemispheres. This technology basically gets rid of the need for a polar alignment scope.

The supplied 17 pound counterweight is locked in place with a single hand-tighten knob, making it easy to rebalance a scope if you add heavy photographic accessories. If needed, optional counterweights are available to balance very heavy loads.

For observing or imaging objects near the meridian (the imaginary line passing directly overhead from North to South), the CGX is designed to track 20° past the meridian for uninterrupted imaging through the most ideal part of the sky.

There are nine motor drive speeds: 0.5x and 1x sidereal for guiding; 4x, 8x, 16x, and 64x for centering; and 1°, 2°, and a fast 5° per second for slewing. Preset tracking rates include sidereal, solar, and lunar. Equatorial tracking modes are available for both northern and southern hemispheres.

New for the CGX mount is a telescope control software that has been developed in conjunction with Planewave Instruments. Planewave Instruments produces some of the most sophisticated imaging systems on the planet. The features of the included software are extremely robust. They include multi-point go-to modeling, focusing, and plate solving. ou will no longer need a third party advanced PC control software as this has it all.

The supplied NexStar computer hand control has a built-in database of more than 40,000 stars and objects. 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; selected variable stars; non-planetary solar system objects; and asterisms.

You can also store and edit the right ascension and declination of 100 additional user-defined objects of your own choosing, such as the comet and asteroid coordinates published monthly in Astronomy and Sky & Telescope magazines. The computer control can find any of those objects with only a few keystrokes, and track them with high accuracy for visual or photographic applications. There is enhanced information on over 200 of the most note-worthy objects.

The NexStar hand control provides a constant digital r. a. and dec readout of the scope's position on the sky. This provides much greater accuracy than conventional 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.

The software built into the NexStar hand control includes mount calibration, database filter limits, hibernate, five alignment procedures, user-defined slew limits, a new "All-Star" polar alignment routine that uses any bright star for a quick and accurate polar alignment, and more. Built-in adjustable backlash compensation permits precise corrections during astrophotography and when observing visually at high powers. A high precision pointing subroutine in the computer lets you point accurately at objects that you want to photograph that are too dim to be seen though the scope.

The software includes permanent programmable periodic error correction (PEC) to correct for the minor periodic tracking errors inherent to all worm drives that might otherwise mar your long exposure photographs. The CGX mount retains the PEC recordings when it is powered down. 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 CGX mount always at the cutting edge of technology.

An autoguider port is located on the electronic pier for long exposure astrophotography. The autoguider port can use a six-pin RJ-12 modular jack ST-4 compatible CCD autoguider to automatically control the drive motors during long exposure astrophotography.

Five different alignment methods are built into the Celestron mount's NexStar computer: 2-star align, quick align, 1-star align, last alignment, and solar system align. This allows you to choose a level of computer accuracy in automatically finding objects with which you are comfortable. Alignment is easily accomplished in only a few short minutes. You can be observing in less than 15 minutes after you first take your CGX-mounted scope outdoors.

In addition, the NexStar computer hand control is GPS-compatible (using an optional inexpensive SkySync GPS module) for full GPS (Global Positioning System) accuracy. Adding GPS to the computer is something no competitively-priced mount can do. Once the scope is approximately polar aligned, the 16-channel SkySync GPS system uses signals from government satellites to calculate the scope's location on earth with an accuracy measured in meters. The system also calculates the current time based on the split second accuracy of the GPS time signals.

After the SkySync quickly completes these calculations, and enters the information into the computer control for you automatically, the computer then orients the scope with the sky, slews to a pair of guide stars, asks you to confirm that the stars are in the center of the field (and center them if they're not precisely aligned), and then starts finding and tracking over 40,000 objects for you at your command. With the Celestron CGX go-to mount and the SkySync, orienting your scope in time and space on earth and aligning it on the sky becomes almost as easy a task as simply turning the mount on.

The new, 2" diameter adjustable height tripod has graduated markings on the legs to help with quick leveling.The center leg brace is drilled to form a convenient accessory tray that holds 1.25" and 2" eyepieces to keep them up out of the dew-soaked grass.

Optical tubes are installed on the CGX mount using a Dual-Slot on the mount head that accepts either a Celestron CGE-style or Losmandy D-plate dovetail slide bar or the narrower Vixen-Style dovetail. This allows the optical tube to be quickly and precisely balanced fore and aft on the mount, 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.