Celestron 8" SC RASA astrograph tube 8 inch (203 mm) (Rowe-Ackermann Schmidt Astrograph) RASA telescope is a high brightness telescope designed specifically for astrophotography needs. Due to the short construction length, it is more stable on the equatorial mechanics than longer built tubes of other systems. Celestron's SC RASA astrographs are available with an 8-inch version that can be connected to an astronomical CCD camera or a mirrorless MILC camera by purchasing a special adapter, while DSLRs can be attached to the larger models.
The telescope is so specialised for astrophotography that there is no visual curiosity. A four-lens corrector with a low colour dispersion ED lens element results in an almost completely coma-free and plane-corrected image with no colour aberration, of course. With its huge F/2 aperture, it collects up to 8x more light in a given unit of time than a system with an F/5.6 aperture. The optical design of the Celestron 8" SC RASA astrograph tube allows it to be sensitive to 390-800 nm, covering a much wider range than usual.
The manufacturer has taken maximum account of the needs of astrophotographers which is why the telescope has a FeatherTouch focusing ring with enhanced precision, supported at six points to eliminate the effect of mirror tilt. A built-in 12V cooling fan ensures optimum cooling, while filtered vents allow the mirror to quickly adapt to ambient temperatures. Special mention should also be made of the practical, robust handle on the tube.
The basic accessory is the company's proprietary StarBright XLT coating, which increases the light-harvesting power of the binoculars. When used, the corrective lens has a transmittance of up to 98%, while the main mirror has a reflectance of 95%.
The Celestron tubes are hand-figured and hand-matched, which means that they consistently outperform the optical quality of competing SC tubes in various tests.
