I am a bit perplexed by high prices of really narrow band filters (like AstroDons). I presume they are worth it based on how many people go for them. I understand that the narrower the bandpass, the cleaner the emission line picked up. However, we are not doing spectroscopy here, so I wonder what these filters buy for the NB Astro-imager.
I have a dual band NB filter that does a good job of cutting out most of LP and moonglow and catches the HA & OIII bandpasses well. It is inexpensive and therefore, has relatively wide bandpasses of 12nm for HA and ~30nm for H-Beta to OIII. The cut-offs of bandpasses seem to be sharp enough that there is not stray emissions picked up beyond the bandpass widths.
So, can one achieve similar final quality images as from even narrower band filters if I extract the Red (HA channel) and the OIII channel (G&B channels) separately and later recombine them? I presume the answer is "No", but I do not understand why that should be the case. That is, what is the magic about very narrow band filters that gives us the wonderful images (of course at a large expense for filters, longer exposures required etc). Your help will be most appreciated ..... Anil
Edited by AKHalea, 18 September 2019 - 05:41 PM.