Mikolaj Wadowski · Aug 22, 2025, 12:24 PM
I could only imagine the wider bandwidth filters could be useful for galaxies with significant redshift and for those you usually need a very large scope, as they’re far away.
I see you’re using a f2.8 lens. I think, though I haven’t done the math, that 3nm filters will give you a better or at least similar SNR to 7nm filters despite the bandshift, as the 3nm filter blocks >2x more unwanted light.
If you ever see yourself building a second rig to run alongside your main one, leaving these filters will save you some money. If you don’t I’d sell them.
Ok, so for galaxies i think wider bandwidth could be a better way, i will try that, and funny that you also mentioned very large scope, i have a large scope, 10”, that i bought it mainly for galaxies although i leave under Bortle 8/9, and i am thinking about buying even larger scope in future but for planetary or everything, so maybe your point about keeping it for those situations could be a good idea.
I have different lenses, but larger one i have as prime lens is 300mm f2.8, i do have 135mm f2 and 85mm f1.8 and even 50mm f1.4, so i am not limited with aperture of lenses, same with telescopes, i do have a Newt with f4, i can use a reducer to bring it to ~f2.8, so that i also keep thinking about those cases i am using fact optics, but the last point you mentioned is what making it confusing decision.
Your point about building a second rig is a point to be taken, but i am building multiple rigs for different reasons, one reason is to take RGB completely separated, so this is the thing i am thinking about, if that fast optics will have redshift, is that affecting the nebulosity or the stars, if stars then simply i am removing stars from SHO data and adding RGB ones, hence i ask if using 7nm/6.5nm is any useful if i am going to use RGB data anyway, i don’t want to rush a decision now and later i find out that 7nm/6.5nm can be handy for something more than 3nm-5nm filters.
