Which light pollution filter or narrowband filter with Hyperstar?

[vincentnm]

Hi All,

Wondering which is a good light pollution filter or narrowband filter with hyperstar? At f1.8, the shape of light cone is rather obtuse, and the normal rules around filters just dont work. Need some anslysis as to why this is different and what the fundamentals are.

1) SteveL was having problems with a narrowband Ha, due to band shifting.

2) Someone else had to use a widepass Ha filter (38nm) with the hyperstar to get decent results.

3) Greg Parker recommends an IDAS LPR rather than a CLS.

What is the common reasoning/principles behind all of these? Would appreciate some insight and some tips in choosing a filter for my hyperstar.

Thanks,

Vincent.

[PeterW]

Good luck, you might want to ask Astronomik, they have specs of the F-ratio they recommend for their filters. But with f1.8 you'll need the broader band to ensure you don't get vignetting and band loss as you mention.

All the best

PEterW