![]() To minimize any potential diffraction spike around the brightest stars, camera cables can be positioned to cross the aperture in a curved pattern, rather than a straight line. Camera cables which cross the front of the RASA 8 do not block much light and, don’t have a significant effect on images.What about camera cables in front of the optics?.For DSLR imaging, we recommend the RASA 11. Also, the DSLR requires too much backfocus (55mm) for the RASA 8, so the camera sensor cannot be placed at the required location relative to the astrograph. The body size of a DSLR is too large compared to the front aperture of the RASA 8, and therefore blocks too much of the incoming light.Why can’t a DSLR be used with the RASA 8?.Color or monochrome sensors can be used, although color sensors are easiest to use since the RASA 8 cannot accommodate a filter wheel (see question #7). ![]() Two key considerations are the size of the camera body (should not exceed about 120mm in diameter), and the camera’s backfocus distance (cannot exceed 25mm). It also works well with mirrorless digital cameras. The RASA 8 can be used with many astronomical CMOS and CCD cameras.What cameras can be used with the RASA 8?.As long as the camera body does not greatly exceed about 120mm diameter, the effect on images is negligible. If the camera body is larger than this, then it will block some of the incoming light. If a camera’s body is smaller than this, it will not block any light from reaching the camera sensor. The lens assembly has an outer diameter of 93mm. The RASA 8 optical design has its own central obstruction which is caused by the sub-aperture lens assembly at the front of the telescope.Won’t the camera block the incoming light?.This necessitates the camera having to be mounted at the front of the astrograph. The RASA 8 optical design uses a prime focus focal plane position in order to obtain its super-fast F/2.0 focal ratio.Why was the RASA 8 designed to have a camera mount at the front of the telescope?.The RASA 8 is an astrograph designed specifically for deep-sky astronomical imaging. Therefore, you cannot look through the RASA 8 with your eyes because your head will block the light from entering the telescope. The optics produce an image at the front end of the telescope, not the back.Why can’t the Rowe-Ackermann Schmidt Astrograph (RASA) 8 be used visually?. ![]()
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