Celestron’s RASA 8 Schmidt Astrograph

FAST OPTICS ARE LIKE FAST CARS: Both are a thrill to experience firsthand. I have some previous experience with fast astrographs and thus was very enthusiastic when the opportunity arose for me to try out Celestron’s new f/2 20-cm (8-inch) Rowe-Ackermann Schmidt Astrograph (RASA 8). Just as with a fast automobile, though, there’s little tolerance for sloppy driving when it comes to operating this instrument.

The RASA 8 is an optical design inspired by the classic Schmidt camera, in which a piece of film is placed at the prime focus of the primary mirror. While Schmidt cameras produced well-corrected stars across a piece of film using a custom film holder that curved the film to match the curved focal plane of the instrument, the RASA design flattens the focal plane with a set of corrective optics located near the camera’s focus point. From a distance, the RASA 8 looks a lot like one of Celestron’s Schmidt-Cassegrain telescopes (SCTs), but as you get closer you’ll notice some significant differences. The most obvious one is that a camera