User manual
Celestron CGEM II 800 8" f

User Manual for Celestron CGEM II 800 8" f 2.0 Rowe-Ackermann Schmidt GoTo EQ Astrograph

• Product category: Catadioptrics (Cassegrains) Celestron
• Brand: Celestron
• Description and content of package
• Technical information and basic settings
• Frequently asked questions – FAQ
• Troubleshooting (does not switch on, does not respond, error message, what do I do if...)
• Authorized service for Celestron Catadioptrics (Cassegrains)

Product description

• 8" f/2.0 Rowe-Ackermann Schmidt Astrograph (OTA Only) 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.
  Optical Performance
  • • 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
  StarBright XLT Coating System
  • • 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
  Focuser
  • • 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
  Mounting
  • • 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
  Included Accessories
  • • 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
  UPC: 050234910736
• CGEM II GoTo EQ Mount with Tripod Celestron updates their venerable and versatile mid-level mount with the CGEM II GoTo EQ Mount. Engineered to carry a 40-pound payload and high-torque dual DC servo motors, it is able to smoothly and accurately slew and track heavier optical tube assemblies (OTAs) and rigs up to an 11" Schmidt-Cassegrain. Its Vixen/Losmandy dual dovetail saddle makes the mount compatible with most plates used today. Celestron also improves its usage by adding compatibility with their SkySync GPS unit for a higher level of precision during setup and alignment. To provide a stable platform for the mount and your OTA, a heavy-duty stainless steel tripod is included that sports large 2" legs and an accessory tray that doubles as a stabilizer.The brain of the CGEM II is the NexStar+ computer controller. Equipped with a database of 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 added for custom object lists. Its intuitive menu-driven user interface provides the power to observe the heavens with nine slew speeds and three tracking rates, plus anti-backlash compensation and Permanent Periodic Error Correction (PPEC) for smoother movements in the motors and improved tracking over time. Features such as guided tours, extended information on 200 popular objects, and multiple alignment options make the NexStar+ controller easy to use and invaluable to new users and experienced stargazers.
  Mount
  • • German equatorial mount
    • 40-pound payload capacity
    • 15-70° latitude adjustment range
    • Dual-axis low-cog DC servo motors with optical encoders for smooth tracking and quiet operation
    • High-torque motors provide smooth tracking and slewing for heavy OTAs
    • Autoguider port for making corrections while astroimaging
    • Dual Vixen/Losmandy dovetail saddle, compatible with CG-5 and CGE bars
    • Long clutch levers make tightening and loosening of clutches easier for manual movement
    • Internal cables/wires for snag-free operation
    • GPS-compatible with optional SkySync unit
    • Runs on included 12 VDC, 3.2A car/vehicle power supply
  NexStar+ Hand Controller
  • • Features:
    • Intuitive menu-driven user interface
    • Nine Slew Speeds: 2x, 4x, 8x, 16x, 32x, 0.3°/sec, 1.0°/sec, 2°/sec, 4°/sec
    • Multiple Tracking Rates: Sidereal, Lunar, and Solar
    • Anti-Backlash Correction: Trains out intrinsic play in gears for smoother movement and tracking
    • Permanent Periodic Error Correction (PPEC): Improves tracking precision for long-exposure astrophotography and imaging
    • Database:
    • 40,000-object database
    • 100 user-defined objects for customization
    • Filters for creating custom object lists
    • Solar system: All seven planets plus the Moon, Sun, and Pluto
    • Custom lists of all the brightest stars, double stars, variable stars, and asterisms
    • Custom lists of all the best galaxies, nebulae, and clusters as well as the complete Messier catalog and select NGC objects
    • Functions
    • Alignment options: One- or Two-star, Solar system, Quick, and Last
    • Sky Tour: Based on location, date, and time, the system shows the best objects in the sky and automatically slews to them
    • Object Info: Provides useful information about the selected object such as magnitude and constellation; includes extended information about 200 popular objects
    • Physical characteristics:
    • 2-line, 16-character LCD window with red backlighting for comfortable viewing without affecting night-adjusted vision
    • 19 function keys, backlit in red
    • Micro-USB port: Connect to a computer, for use with software programs for point-and-click slewing capability and updating firmware via PC
  Tripod
  • • Stainless steel legs
    • Heavy-duty 2" diameter
    • Graduated markings on lower section for height repeatability
    • Accessory/eyepiece holder tray that doubles as leg spreader/lock
    • Weight: 20 pounds
  UPC: 050234915236

• 42mm Camera T-Adapter

• C-Thread Imaging Adapter

• Fan Battery Pack

• Limited 2-Year Warranty

• NexStar+ AZ Hand Controller

• 17 lb Counterweight for the CGEM EQ Mount

• Stainless Steel Tripod

• Counterweight Shaft

• NexRemote Software DVD

• 12VDC Car/Vehicle Power Adapter

• Limited Two-Year Warranty

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Technical parameters

• 8" f/2.0 Rowe-Ackermann Schmidt Astrograph (OTA Only)

  Optical Design	Rowe-Ackermann Schmidt
  Aperture	8.0" / 203mm
  Focal Length	400mm
  Focal Ratio	f/2.0
  Back Focus	With included camera adapter: 0.98" / 25mm From top of threaded collar: 1.14" / 29mm
  Eyepiece Barrel Diameter	N/A
  Diagonal	None
  Finderscope	None
  Tripod	None
  Mount Type	Losmandy-D/CGE dovetail plate
  Power Requirement	8 x AA batteries 12VDC, 100mA power adapter
  Dimensions	Length: 24.7" / 62.8 cm Diameter: 9.3" / 23.5 cm
  Weight	17.0 lb / 7.7 kg

• CGEM II GoTo EQ Mount with Tripod

  Mount Type	Equatorial
  Load Capacity	40.0 lb / 18.1 kg
  Motor	Dual-axis low-cog DC servo
  GO-TO Capability	Yes, NexStar+ hand controller
  Latitude Adjustment Range	15 - 70°
  Polar Axis Scope	None
  Includes Tripod/Pier	Adjustable-height stainless steel 2"-diameter legs
  Power Source	12 VDC, 3.2 amps
  Weight	Mount: 40.0 lb / 18.1 kg Tripod: 20.0 lb / 9.1 kg Total: 77.0 lb / 34.9 kg

  Box Dimensions (LxWxH)	42.5 x 19.8 x 13.1"

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