127mm maksutov

[nightfisher]

What size is the central obstruction on a 127 mak, and what does this leave as clear aperture please?

[Alkaid]

I read somewhere that the effective aperture is 117mm.

[Stu]

Looks like the central obstruction is about 40mm from this post Jules

That's around 31% of the diameter and about 10% of the area

I think the 117mm refers to the fact that the front plate diverges the incoming light and so overfills the 127mm primary which effectively loses light. This doesn't factor in the central obs as well as far as I can see.

Stu

[nightfisher]

cheers for that

[JamesF]

I measured the obstruction for a post the other day and now I can't find it I'll go and do so again.

James

[JamesF]

It is indeed very close to 40mm.

James