16 May
2007
16 May
'07
10:13 a.m.
Good point. If the secondary mirror is 3X, then moving the primary 1mm will move the focus 3mm. If the secondary is 4X, moving the primary 1mm will move the focus 4mm, and so-on. Quite a bit of leverage available. Generally, when SCT's are used for imaging, a German equatorial mount is preferred. The reason for a short-coupled camera is usually lack of swing-through room on a fork mount. On 5/16/07, daniel turner <outwest112@yahoo.com> wrote:
The SC is generous with back focus. This is because the focal length and focal ratio are variable.