Bahtinov masks

[spacebloke]

Hello everyone,

Is a bahtinov mask specific to each telescope?

I have one for my 6se and I now have a 80ed ds pro and wondered if I need to buy a new one.

Cheers

[Stephen]

They are specific to the focal ratio of the scope.

[Martin-Devon]

Check out the FLO website - they do a wide range of masks specific for aperture & F ratio. If your one is not listed, they will custom request a mask for you - this is what they did for my mask to fit the Ikharus refractor I have of 102mm/F5.6 at no extra charge.

[spacebloke]

If the focus mask is specific to the f-ratio would it make a difference if I was using a focal reducer?

[Stephen]

If the focus mask is specific to the f-ratio would it make a difference if I was using a focal reducer?

Strictly speaking yes, though I don't think many people buy one for each focal length.

There was a thread about it previously, but I can't find it at the moment. You can use differing masks, but the final "result" isn't going to be as precise as one designed for the correct f ratio.

Keith (who makes the masks) had this to say when I asked about the difference between a f5 and f5.91

Hi Stephen, it should still work just not 100% as the right one would. I use a C925 which is f10 and can just about get away with using the f10 mask when I am using the scope with a reducer at f6.3. The same with my Williams 102ED which is f7 but I now use a reducer on that at f5.6 and it still works okay.