Celestron 8" SC RASA astrograph optical tube The 8-inch (203 mm) Rowe-Ackermann Schmidt Astrograph RASA telescope is a fast optical system designed specifically for astrophotography. Its compact optical tube provides greater stability on an equatorial mount than longer optical tubes of other designs. The 8-inch Celestron SC RASA astrograph can be connected to an astronomical CCD camera or a mirrorless MILC camera with a separately purchased adapter, while the larger models can also accommodate DSLRs.
This telescope is so highly specialized for astrophotography that it does not even feature a visual back. Its four-element corrector, incorporating a low-dispersion ED lens element, delivers an almost entirely coma-free and flat-field corrected image, naturally without chromatic aberration. Thanks to its exceptionally fast f/2 focal ratio, it can collect up to 8 times more light in the same amount of time than an f/5.6 system. The optical design of the Celestron 8" SC RASA astrograph optical tube also provides sensitivity across the 390–800 nm range, covering a far wider spectrum than usual.
The manufacturer has fully considered the needs of astrophotographers, equipping the telescope with a high-precision FeatherTouch focuser supported at six points to eliminate the effects of mirror tilt. An integrated 12 V cooling fan ensures optimum cooling, while filtered ventilation openings allow the mirror to quickly reach ambient temperature. The practical, sturdy carrying handle on the optical tube also deserves special mention.
The standard accessory is the company's proprietary StarBright XLT coating, which enhances the telescope's light-gathering efficiency. With this coating, the corrector lens achieves 98% light transmission, while the primary mirror provides 95% reflectivity.
The optics of Celestron optical tubes are hand-finished (hand-figuring) and hand-matched, which, according to various tests, consistently results in superior optical quality compared to competing SC optical tubes.
