Celestron put together the GEM II 800 8" f/2 Rowe-Ackerman Schmidt Astrograph GoTo Telescope to provide a complete observational platform that includes a large-aperture optical tube assembly (OTA), the NexStar+ computer hand controller, a motorized equatorial mount and tripod, plus an array of accessories to get you set up and observing the moon, planets, and especially deep-sky subjects like nebulae, galaxies, and star clusters.
The Celestron 8" f/2.0 Rowe-Ackermann Schmidt Astrograph (RASA) is specifically designed for astrophotography and astro-imaging with a large aperture and fast focal ratio. Using four-element rare-earth optical glass lenses ensures accurate color rendition and eliminates aberrations such as coma and field curvatures. The improved StarBright XLT multi-coating system, which includes anti-reflection coatings on the lenses and highly reflective coatings on the mirrors, increases light transmission throughout the entire optical path. An integrated fan reduces cooldown time and provides optimal airflow through the optical tube assembly (OTA) while filtering harmful dust from the interior.
The astrograph design is defined by its fast focal ratio, which reduces exposure times without sacrificing image quality and gives you more time for multiple shots of the same object for layering or with different filters. Its internal Ultra-Stable focusing mechanism enables very precise focusing to clearly resolve topographic details on the Moon or split double stars and reveal details of most other celestial objects in between, while minimizing unwanted lateral movement of the primary mirror when focusing or slewing. Since this OTA is designed as an imaging scope, a 42mm camera T-adapter and C-mount imager adapter are included that are compatible with most camera-specific T-rings that are widely available.
- 203mm (8") diameter aperture enables near- and deep-sky viewing without being prohibitively large or heavy for easy transport to viewing locations
- 400mm focal length helps to produce a fast focal ratio
- Fast f/2.0 focal ratio requires significantly lower exposure times versus slower ratios to produce the same results
- Rowe-Ackermann Schmidt astrograph (RASA) design is purpose built for astrophotography and imaging performance, and is not recommended for visual use
- Proprietary StarBright XLT fully multi-coated optical system
- Four-element rare-earth glass for true color rendition without aberrations across the entire field of view
- Wide 390-800nm spectral range improves images of deep space objects like galaxies and nebulae
- Image circle: 22mm (0.86")
- Resolution: 0.68 arcsec (Rayleigh), 0.57 arcsec (Dawes)
- Back focus: 25mm (0.98") with included camera adapter, 29mm (1.14") from top of threaded collar
- Optical window can be removed and replaced with optional filters such as a light pollution filter
- Integrated cooling fan brings optical system to ambient air temperature for better performance
- Runs on eight user-supplied AA batteries or optional 12VDC power adapter
- Multi-layer mirror coatings made from layers of aluminum, SiO2 (silicon dioxide), and TiO2 (titanium dioxide)
- Reflectivity is flat across the light spectrum, for both astrophotography/astro-imaging
- Multi-layer anti-reflective coatings made from layers of MgF2 (magnesium fluoride) and HfO2 (hafnium dioxide)
- High-transmission water white glass corrector lens with 97.4% light transmission
- Focusing system moves primary mirror forward and back to achieve tack-sharp images
- Ultra-stable design minimizes unwanted lateral movement of the primary mirror when focusing or slewing
- Fine adjustments for precise focusing, approximately 30 turns of the knob runs through the focus range
- OTA only, mount and tripod required for proper use
- Includes large CGE/Losmandy-D dovetail plate for use on larger more stable mount heads
- Weight: 17 pounds
- Standard M42 camera T-adapter accepts most camera-specific T-rings to directly mount DSLR and mirrorless cameras
- CCTV/Imager C-thread adapter accepts most camera-specific video T-rings to mount imaging and video cameras
- Battery pack takes eight user-supplied AA batteries to power the integrated cooling fan
Engineered to bridge the gap between their Advanced VX & heavy-duty CGX-L mounts, the Celestron CGEM II GoTo German Equatorial Mount delivers the performance required for capturing clear images during astrophotography sessions or resolving dim details when observing through an eyepiece. To make it compatible with a wide assortment of optical tube assemblies, Celestron outfitted the CGEM II with a dovetail saddle designed to accept the standard Vixen-style (Celestron's CG-5) and the larger Losmandy (Celestron CGE) dovetail bars.
Through the use of high-torque dual-axis low-cog DC servo motors, optical encoders on the motors, backlash compensation, and Permanent Periodic Error Correction (PPEC) the mount is capable of precise positioning and tracking accuracy to ensure your target object stays centered while constantly improving its performance the more you use it.
The brain of the system is the NexStar+ computer controller, which is equipped with a database of over 40,000 objects, including the planets, stars, nebulae, galaxies, and the complete Messier catalog; it can also be programmed with up 100 custom user-defined objects with filters to create custom object lists. Its intuitive menu-driven user interface makes observing the sky, day and night, fast and easy. Features such as guided tours, extended information on 200 popular objects, and multiple alignment options make the NexStar+ controller an invaluable tool to new users and experienced stargazers alike.
- 40-pound payload capacity
- Uninterrupted tracking below meridian to enable observation from a raised location such as a balcony or hilltop
- Internal cables eliminate snag hazards in the dark or when operating the mount remotely
- Counterweight bar with 17-pound counterweight allows you to properly balance your OTA with accessories and imaging systems
- Dual CG-5 (Vixen) and CGE (Losmandy) dovetail saddle make it compatible with most large and small OTAs on the market
- Dedicated autoguider port for making corrections when astroimaging
- Runs on the included 12V DC power cord
- Dual-axis low-cog DC servo motors
- High-torque motors for helping to smoothly drive heavier loads
- Dual motor encoders improve tracking and location accuracy with reduced vibrations
- Clutch levers for manual movement, levers are longer than normal to make tightening and loosening easier
- 40,000+ object database with filters for creating custom object lists
- 100 user-defined programmable celestial or terrestrial objects
- Enhanced information on over 200 objects
- Nine slew speeds: 4°/sec, 2°/sec, 1°/sec, 0.3°/sec, 32x, 16x, 8x, 4x, 2x
- Three tracking rates: Sidereal, Solar, Lunar
- Solar System alignment method allows to view the moon and planets during the day
- Built-in polar alignment program to polar align on any star in the sky
- Sky Tour Mode: System seeks out the best objects for the date and time and automatically slews to them
- Identify Mode: Use to identify an unknown object in the field of view, or to find other celestial objects that are close to where the user is viewing
- Anti-backlash compensation: Trains out the intrinsic play between gears for more precise slewing and tracking
- Permanent Periodic Error Correction (PPEC): System learns its internal tracking errors and improves over time for more precise tracking, requiring fewer corrections
- Built-in instructions guide you through the alignment procedures
- 4-line, 18-character LCD display with a 19-button fiber-optic backlit LED keypad
- RS-232 communication port on hand control to control the telescope via a personal computer
- Supports English, French, Italian, German, and Spanish
- Solar system: Seven planets, moon, sun, and Pluto
- Custom lists of all the brightest stars, double stars, variable stars, and asterisms
- Custom lists of galaxies, nebulae, and clusters, as well as the complete Messier catalog and select NGC objects
The Celestron CGEM II Tripod has 2" diameter steel legs with graduated markings that make it easy to extend the legs to the same height. It comes with a 17 lb counterweight.