Secondary advice wanted.
Hi all,
I have an 8" F/7 dob so basically a 203mm FL1447.8mm Newt. The tube Dia is 254mm. I worked out that the focuser is 70mm from tube to where the ep should focus this includes a 10mm spacer needed to focus at about the same distance as the old focuser. I used the formula Secondary to Eyepiece distance which was 197mm then used the formula mirror diameter divided by the focal length times 197mm, which equals 27.2mm This resultant is the diameter of the short diameter of the secondary (theoretically) I measured the one in the scope and it is 40mm in dia.
Given this I have a secondary which is 1.47 times bigger in the scope that is theoretically needed, and as we know the smaller the obstrution the better the image. What are your thoughts on this, I am tempted to buy a smaller secondary and spider assy, but don't really want to if it wont make much difference.
Has anyone thought about this or had a similar situation?
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