Beginner question on filter size

[choochoo_baloo]

I bought a mono CCD a little while ago, and am researching filters to go with it.

The filter wheel I bought S/H has a 2" carousel. I

s there a reference for knowing which filter size (1.25", 2", 36mm etc) can serve what sensor, without vignetting? If I'm going to stick with a small sensor for a while, then there's no need to buy the bigger filters, when the smaller/cheaper behave identically.

Thanks.

[Davey-T]

If you can remember your schoolboy maths you can work it out, something to do with half arc tan or some such 

Dave 

[choochoo_baloo]

13 hours ago, Davey-T said:

If you can remember your schoolboy maths you can work it out, something to do with half arc tan or some such 

Dave 

Can you elaborate please? Why is arctan needed if we're only concerned with the hypotenuse in the same plane?

I also thought there must be increments to allow for edge effects from the filter frame etc

[Davey-T]

Over 60 years since I was at school so don't remember much I think the theory was done with a pinhole camera and half angle as it was easier to work out but can't remember much else.

Dave

Edited December 17, 2019 by Davey-T

[MarcusH]

FLO to the rescue 😉 :

https://astronomy.tools/calculators/ccd_filter_size

 

[choochoo_baloo]

1 hour ago, MarcusH said:

FLO to the rescue 😉 :

https://astronomy.tools/calculators/ccd_filter_size

 

THANK YOU Marcus. I was getting very frustrated at there not being a straight forward calculation. This is even better