Hello
I'm interested in trying to observe some of the brighter Herbig-Haro objects. It seems to me that HH 1 and 2 are tangible targets for an 18", as are possibly HH7, HH11 and HH12. Various sources report that HH32 is the brightest, but it seems to be a bit off-season.
From the looks of it, these are hydrogen emissions. Do they also have a good amount of OIII? What filter should I tend to prefer? Of course, I will try both, so maybe this question is moot, but it would still be interesting to know the physics of good filtration.
Clear Skies
Regards
Akarsh