After a couple April Supernova images I'm back to processing in order taken. This is my first image finished in 2016 (H alpha data) the LRGB data was taken mostly in October, 2015.
Abell 82 is a planetary nebula in western Cassiopeia about 1000 light-years by the only measurement I could find. The central star is a puzzle being a K0 sub giant star by this paper http://www.aanda.org...3984-09/T4.html . Their table lists two K0 and two K3 stars along with a few M class central stars. This goes against the central star being a white dwarf so what's wrong? A K0 sub giant shouldn't put out enough UV to excite a SN. Besides, its the outer envelope being blown off that forms the PN yet a K0 star still has its outer shell. I have no idea how this can happen. Is the central star a double star in which the white dwarf is swamped by the much brighter giant or sub giant star? Is the central star too faint and there just happens to be a handy nearby one that gets tabbed for this? The planetary's size in my LRGB image is 80" of arc which makes it about 0.39 light-years across. This doesn't consider the faint ears seen in OIII light. They give it a diameter of about 113" for a size of 0.55 light-years assuming the 1000 light-year distance is correct. Lots of ifs in this so the error could be substantial.
I had started this one years ago but only got a couple frames. Somehow it never was finished until I was reminded of it by a narrow band post by Derek Santiago http://www.pbase.com...image/160958220 . That got it back on my to-do list. Last October I managed to get it in LRGB and then in January get some H alpha data. Not having an OIII filter I wasn't able to pick up the "ears" that Derek did. Not having seen anyone try it in LRGB I had to see what that would show. I then added the H alpha data which pretty much wiped out the OIII even in the parts where OIII is stronger than H alpha since I couldn't isolate that frequency. Adding the H alpha brought out its classic "apple core" appearance. Each has something to offer. Note that the H alpha filter at 6nm bandwidth also picks up NII emission which is often found in planetary nebula. How much of the red is H alpha and how much NII I don't know.
There's nothing else in the field worth mentioning that I noticed so I didn't prepare an annotated image.
14" LX200R @ f/10, L=4x10' RGB=2x10', HA=4x30', STL-11000XM, Paramount ME
Attached crops are at 0.8" per pixel