Dob Masking..guides?

[estwing]

Does anyone know of a written guide/chart or rulebook on app+focal length=mask hole size? my 12.5" 1525mm F4.8 how do i work out the best size hole to use,or should i choose to have a couple of size holes so to try out which suits my telescope the best,sorry if its an easy answer that i've overlooked..

[swamp thing]

I would just make the biggest hole you can that avoids the secondary obstruction.

[Optical Dob]

I think Moonshane uses masks on his Dobs sometimes.

[Moonshane]

basically what Steve said but I usually do them with at least two holes. one as large as possible whilst missing the secondary / vanes and the other perhaps 75% of that size or so.

e.g. with my 16" f4, I have 170mm f11, 130mm f14 and 100mm f18 (figures include the paracorr effect on focal length).