[luka]

Hi

I may be able to get hold of a special H alpha filter. Originally this was not an astronomical filter and has 50.0mm diameter and transmission FWHM of 0.5nm, i.e. it is extremely narrowband. I believe it is about 6-7mm thick (to be confirmed). It does not have any threads for mounting, just a metal ring on the outer diameter.

Any ideas how to mount such filter? Currently I use ED80 + Hotech SCA flattener + T-ring + DSLR (IR modified).

Also would FWHM of 0.5nn be a problem? I can imagine it would completely kill the light pollution :-)

Thanks
Luka