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Old 24-10-2016, 09:16 AM
dave brock's Avatar
dave brock
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Join Date: Dec 2011
Location: hamilton nz
Posts: 83
If they are different then both the reflection of the primary and the outside of the secondary would be not the same (concentric) as viewed from the focuser, particularly in large fast scopes. Your 10% would stick out like a sore thumb. If they do not look the same (circular) then there is a tilt or rotational error present in the secondary. Google image telescope collimation and see for yourself.

Dave
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