Celestron RASA 8 Rowe-Ackermann Schmidt Astrograph OTA
8" Rowe-Ackermann Schmidt Astrograph, 400 mm f/2.0, 22 mm Ø (3.15°) image circle, CGE dovetail.
The Rowe-Ackermann Schmidt Astrograph (RASA) is a dedicated imaging telescope: the camera sits at the front of the tube, at prime focus, giving an extremely fast focal ratio and a flat, colour-corrected field. Exposures are a fraction of those needed at f/7–f/10, and short exposures often make autoguiding unnecessary. Imaging only, not for visual use. Check that your camera's body is small enough for the front-mounted position (dedicated astro CMOS cameras are ideal; most DSLRs are not suitable).
Optical
Optical design
Rowe-Ackermann Schmidt Astrograph (RASA)
Aperture
203 mm (8")
Focal length
400 mm
Focal ratio
f/2.0
Image circle
22 mm Ø (3.15°)
Usable field
32 mm Ø (4.6°), minimal loss at the edge
Wavelength range
400–800 nm
Spot size
< 2.3 µm RMS across image circle
Off-axis illumination
93% at 11 mm off-axis
Coatings
StarBright XLT
Central obstruction
93 mm (46% of aperture)
Optical window
46 mm Ø
Cooling
Integrated 12 V DC fan
Mechanical and package
Back focus with included camera adapter
25 mm with included adapter; 29 mm from top of threaded collar
Focuser
Precision Bearing System (PBS)
Tube length
628 mm
Tube diameter
235 mm
Weight
7.7 kg
Dovetail
CGE dovetail bar
Finderscope
Not included
Included
42 mm (M42) T-thread camera adapter; C-thread camera adapter; fan battery pack
