Hi all long time no post, have spent much time flailing away at planetary (the other kind) imaging and with more success at last year's eclipse (images at my blog).
Here's Abell 33, a spherical planetary nebula with a bright foreground star conveniently superimposed on the edge, providing the "diamond" for the ring:
The small blue star in the center is the white dwarf creating the nebula. A close up of the RGB version (upsampled 2x) shows a hint of a second star to the lower right. This is likely a visual double, as a double central star should (in theory with rare exception) create a bipolar, rather than a spherical nebula.
The RGB image shows two other things:
1. how faint the nebula is, as it was barely detectable on the RGB image, requiring narrow band filters to bring it out.
2. how bright the "diamond" star is as it created a "bloom" on my ABG camera.
should have shot the RGB unbinned to better resolve the central star and minimize blooming.
apparently a currently open issue in astronomy is whether the ratio of PN central double stars matches that of the general stellar population. there are several recent surveys which address this, and may confirm my supposition, but i don't have access to them.
I did take a few trial Ha shots, but got only extremely faint signal in a circle, matching the OIII, but without detail.
image details and larger size at the blog
thanks to derek/schmeah for bringing this one to my attention with his 2016 post
Edited by bill w, 14 February 2018 - 03:17 AM.