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
