Since i get an Ovni-M device from Jonathan’s company (« Joko » in CN), i came to use more and more camera lenses: easier and faster to use, lightweight. This is the best compromise that I have found and that I often enjoy using (and the best one when the sky is clear and that i dont have much time).
I mainly use M42/T2 lenses, with a filter changer (https://www.cloudyni...lchargerslider/), but i also have a few c-mount fast lenses which i really (really) enjoy : a Cosmicar TV 75mm f/1.4 (2,9/3x.) and a superb Computar MC TV 135mm f/1.8 (which gives 5,2x.)
Only (big) problem with the c-mount lenses is i could not use any filter with any of them : the setup has to be really short to reach focus; the filter changer doesnt work, nor short adapters (10mm width).
Then i asked some CN members some help, and Ray (aka GeezerGazer) found the perfect solution :
Make a filter small enough to fit inside the C-mount cavity on my Ovni-M.
In this « yellow part » cavity exactly :
Astronomik propose unmounted filters (12nm and 6nm) of 27mm, that would fit perfectly in there, with a rubber o-ring to avoid problem (they also propose tailor-made filters in the dimensions you want).
Later i have found, thanks to Jonathan who did a few tests with his equipment, that i could actually unmount my 1.25 filters myself (which i didnt know...) :
I did the same with my H-Alpha 7nm and the diameter is exactly 27mm, enough to fit in my Ovni-M device :
Yes, there are certainly drawbacks to using unmounted filters, but it's a real victory in itself to be able to see the sky with a c-mount fast lens AND filters. And as far as I know there is no other way to do it so well (Except with 2’ filters, but with less visual result due to the space between the filter and the NV captor).
I’d like to thanks Ray and Jonathan for their precious help and time. Now i can use my c-mount lenses and enjoy them perfectly.