The Vixen VC200L has a built in 3 element corrector in the baffle tube quite close to the primary mirror which provides for “pin point” images over a large sensor, such as the Canon 40D. Here is the blurb from the Vixen USA website:
“The VC 200L is an 8" f/9.0 highly corrected, highly specialized telescope for astro imaging. The VISAC provides high-definition star images to the edge of a wide viewing field and offers exceptionally outstanding performance in astrophotography.Even at the edge of the 35mm film format (larger CCD chips) stars are sharp ( smaller than 15 micrometers) This is smaller than the resolution of fine quality CCD cameras, which means that the telescope does not limit the image quality. With its elaborate aspherical optical design it achieves an excellent image correction throughout the large illuminated field. (42mm diameter fully illuminated)
With the f/6.4 reducer you get much shorter exposure times. The reducer is a highly recommended optional accessory.”
http://vixenoptics.com/reflectors/VC200L.htm
One other consideration with the VC200L is that it has a rack and pinion focuser so you shouldn’t get any image shift when focusing, but the downside is that back focus is limited compared to SCT’s that focus by moving the primary mirror.
So, it may not be possible to fit, say, a motorised focuser and an off axis guider or flip mirror simultaneously?
Cheers
Dennis
