Quote:
Originally Posted by OzEclipse
Paul,
formula for a simple lens is
[1/OBJECT DISTANCE] + [1/IMAGE DISTANCE] = [1/ FOCAL LENGTH]
Providing you are not changing distance between mirrors, the SCT will conform to this rule.
Cheers
Joe
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Thanks but I dont quite understand, using this:-
1/OD + 1/ID = 1/FL
assuming you mean image distance from the front of the primary which if the image is formed 20cm behind the scope then this would be say 25cm or 250mm. So with a FL of 2350mm I get
1/OD = 1/FL - 1/ID
1/OD = 1/2350 - 1/250 = 0.0004 - .004 = -0.0036
OD = -279mm
So maybe I am not understanding but....the star is about 30 metres from the scope not -279mm.
Cheers
Paul