Celestron 8" SC RASA Astrograph Optical Tube The 8-inch (203 mm) Rowe-Ackermann Schmidt Astrograph RASA telescope is a fast astrograph specifically designed to meet the needs of astrophotographers. Thanks to its compact optical tube, it is more stable on an equatorial mount than longer optical tubes of other designs. The 8-inch version of the Celestron SC RASA astrographs can be fitted with an astronomical CCD camera or mirrorless MILC camera using a separately purchased adapter, while the larger models can also accommodate DSLRs.
The telescope is so highly specialized for astrophotography that it does not even feature a visual focuser. Its four-element corrector, incorporating a low-dispersion ED lens element, delivers an almost completely coma-free and flat-field image, naturally without chromatic aberration. Its exceptionally fast f/2 focal ratio enables it to collect up to 8 times more light in the same amount of time than a system with an f/5.6 focal ratio. The optical design of the Celestron 8" SC RASA astrograph optical tube provides sensitivity across the 390–800 nm range, covering a significantly wider spectrum than usual.
The manufacturer has taken astrophotographers' requirements fully into account, which is why the telescope features a reinforced, precision focusing system supported at six points to eliminate the effects of mirror shift. An integrated 12 V cooling fan ensures optimal cooling, while the mirror quickly reaches ambient temperature through filtered ventilation openings. The practical, sturdy handle on the optical tube also deserves special mention.
The standard accessory is the company's proprietary StarBright XLT coating, which increases the telescope's light-gathering efficiency. With this coating, the corrector lens achieves 98% light transmission, while the primary mirror has a reflectivity of 95%.
The Celestron RASA 8" astrograph features a Losmandy-standard dovetail bar for mounting connection.