|
Hi Peter,
Cassegrains and the different variations ( SCT, Ritchey Chretian, Gregorian, Dall Kirkham etc) are all reflectors that fold back the light cone so it focuses behind a hole in the primary mirror.
However the secondary mirror cannot be a flat mirror, it must have some magnification or else the focal point would never make it past the primary.
Like Newtonian's they also have to be collimated to perform correctly.
Cheers
Bill
|