I've always wondered how sensitive film is to the OIII wavelength, specifically Technical Pan. I've heard a lot about h-alpha, but not a lot about OIII, at least in relation to film astrophotography. Being curious, I bought a Televue Nebustar UHC filter (a narrowband OIII filter seemed way too narrow for film). I used my trusty old Tech Pan, with its fairly even response throughout the whole spectrum and its lack of reciprocity failure. I finally got a clear night, and figured M42 would be a nice bright target with a lot of OIII emission. Well, here are my results. The filter completely removed my light pollution, and the contrast seems increased in comparison to my unfiltered shot. On a different note, my negative seemed a bit fogged, and also there are what seem to be light leaks on the edge of the frame and around the sprocket holes. Could my very old camera or developing tank have light leaks, or could this be some sort of uneven development (I think the film crinkled a bit when I loaded it onto the reel)? Also, has anybody seen the mottled pattern that appears on my shots? I am thinking it could be uneven hypering, but I really have no clue.
Thanks and clear skies,
Exposure: 29 minutes
Lens: 152mm f5.9 Achromat
Film: Hypered Tech Pan
Guiding: Manual w/off axis guider
Also, Excuse the dreadful scan!!