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Hi Rom,
This is the formula
Sec offset = Sec size / (4 * Focal ratio)
This is how much the secondary is offset toward the primary mirror and also how much it should be offset away from the focuser for fully offset collimation.
Anyway if the secondary is centred in the sight tube and you can see the edge of the primary the offset takes care of itself.
Cheers
Bill
Last edited by billdan; 02-10-2016 at 11:58 PM.
Reason: More info
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