Messier 83: Going Deep a New Way

OTA: CDK17"
Camera: =SBIG STXL11002
Observatory: Heaven's Mirror, Aus

Exposures:
R: 12 x 1200 sec
G: 8 x 1200
B: 8 x 1200
L: 19 x 1200
Total Exposure time used: 15.7 hours
Image Width: 41.7 arc-minutes

Processing Tools:
1.    Commercial: PixInsight, Topaz (Studio2, Photo AI2), Aurora HDR, Luminar Neo, 3DLUT Creator, Photo Director
2.    Pixinsight Addons: NoiseXTerminator, BlurXTerminator, StarXTerminator, Normalize Scale Gradient
3.    My Scripts: NB_Assistant, AC_Restar, Subframe Weighting Tool (Excel w/ J. Hunt)

Target Description:
Messier 83 is undoubtedly one of the most stunning galaxies in the S. Hemisphere, if not the entire sky. It is a classic spiral galaxy that is thought to have recently interacted with the dwarf galaxy NGC 5253 (outside the lower left of this image). That encounter spawned a burst of star formation, as revealed by the abundance of young blue stars. It also appears to have enhanced the abundance of gasses at the galaxy's outer edges, perhaps gravitationally displacing it from within the galaxy itself. A halo of gas and dust appears to envelop the galaxy. The halo could have resulted from materials ejected from the star-burst regions that may be similar to the ejected materials we see beyond M82 (https://astrob.in/catu1u/0/), but maybe with fewer embedded young stars that cause M82's Ha emissions.  (There's a second halo, even easier to image, beyond the one discussed.)

Processing Description:
These data were acquired in 2020 to test a newly installed CDK 17. The rig obviously was off to a fine start!

Like many captured image sets, the idea was to provide a ting of color with a modest number of RGB subs and provide most of the detail and contrast with the luminance subs—not what I prefer. The standard method for incorporating L into RGB is to transform the stretched version of the RGB image into Lab color space, replace its L with the independently captured (and stretched) L, and then transform it back to RGB color space. The back-transformation has potential problems because the numeric range of L in the Lab space is unbounded and can cause color saturations if the value exceeds 1.0, and otherwise distorts the color balance of the final RGB image.

I tried using just the RGB data in this image, and the result was unimpressive—actually, unacceptable. So, I developed a new way (for me, at least) of making the separately-captured luminance compatible with the equivalent L in RGB image. The results were just what I had hoped, and a detailed and deep image resulted.

Hope you like it….

Alex Woronow