Phantastic image Rick. This PN just got a much higher rank on my "to do"
list.

Stefan


"WA0CKY" schrieb im Newsbeitrag ...


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/articles/aa/ful...984-09/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 layers intact. 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/dsantiago/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.

There's nothing else in the field worth mentioning that I noticed so I
didn't prepare an annotated image.

First without H alpha data then with H alpha data. Note that my H alpha
filter at 6nm bandwidth also passes NII. How much NII is involved I
don't know. Just that the red is a composite of both elements.

14" LX200R @ f/10, L=4x10' RGB=2x10', HA=4x30', STL-11000XM, Paramount
ME

Rick


--
WA0CKY