So I'm relatively new to amateur astronomy, but one of the first things about this hobby that really caught my interest were nebula filters. I work in a Molecular Biology lab where we routinely use fluorescent tags to label structures of interest, so I am quite familiar with the use of filters to isolate certain wavelengths and just found it very interesting that very similar filters are being used in astronomy.
However, I was a bit disappointed when I noticed the lack of spectroscopic data that is available on the various filters that are sold online. A few vendors will post the bandpass of the filters they sell, but they're often simple cartoon schematics as opposed to actual scans, so it's really hard to know what you're actually buying and if it's worth the extra cost.
With that in mind, I've taken it upon myself to use the UV-Vis spectrometer in our lab to take scans of any and all filters that pass through my hands in an effort to provide as much additional data as possible on some of the more common filters. This analysis is by no means final or comprehensive, but I think I have accumulated enough to stimulate some sort of discussion and hopefully answer a few of the more common questions I've seen come up on this forum. In particular I would like to provide a few insights to the following:
1. Which narrowband "UHC-like" filter should I buy?
2. How consistent is the coating process from one batch to another?
3. Is the performance of my "mottled / rusted" filter compromised by the apparent hazing in the coatings?
I will do my best to provide answers to these questions, but please keep in mind that everything I am about to say is entirely based off scans I've taken on our UV-Vis, so it's purely an analytical approach. I've spent very little time at the eyepiece with these, winters in the NW are a disaster for astronomy, and reports provided by David Kinsely and others will be much better at describing the performance of some of these filters in the field.