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I considered doing this myself a short while ago and calculated the numbers for my GSO 10inch dob.
Standard secondary 63mm
fully illuminated field 16.2mm , 0.75 degrees
75% illuminated 42.4mm , 1.95 degrees
Next smallest standard size is 2.14inch (54.35mm)
fully illuminated field 3mm, 0.25 degrees
70% illuminated 18.5mm 1.49 degrees
To reduce the secondary size here will make a visible difference with widest field eyepieces.
Unless you live in a place where the seeing is great and planetary is your main interest, its not worth the expense of the change.
Last edited by Starkler; 27-03-2005 at 09:49 AM.
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