Bahtinov with a slightly larger scope

[samir_ansari]

Hi everyone,

A while ago I bought a bahtinov mask for my 100mm scope which I now wish to use with my 127mm skymax. Is it a problem if the mask is slightly smaller than the scope's diameter provided I make sure it's smack-bang in the middle?

Thanks for reading,

Samir

[Stephen]

I think it's the f ratio that's more important (though you may need to cover the gap between the mask and the rim of the ota.)

Are both f ratios the same/similar?

[samir_ansari]

Ah I see, thanks for the quick response Kh3ldar! I didn't know the ratio was a factor. My 100mm Celestron is an F9 while the Skymax is F11.81 - is this too much of a jump?

[Stephen]

I strongly suspect so ... (I stand to be corrected!)

[Psychobilly]

It will still work .... you may start to get a spread "spectrum" along the lines but they will still form the cross and moving line.... It's the Focal length of the scope that fixes the spacing...

Peter...