NGC 6164-6165: Oh what that O-Star Did!

OTA:……………….PlaneWave 17” f/6.8
Camera:………….FLI ML16803
Observatory:…. Deep Sky West, Chile

EXPOSURES:                
R: 14 x 600 sec
B: 11 x 600
G: 12 x 600
H: 29 x 1800
O: 18 x 1800
Total exposure:    29.7 hours

Image Width: 40 arc-minutes
Processed by Alex Woronow (2022) using PixInsight, Topaz, SWT

This image presents the Ha and OIII subs mapped to a true-color image of this planetary nebula, NGC 6164. The colors are not what would be captured by an RGB image, nor what you or I would see if we had enough sensitive cones in our eyes to see faint colors. The colors are what you might see if your cones only saw Ha and OIII emission-line colors (a red and teal combination), if, somehow, your eyes could execute a color calibration using the stars surrounding the nebula. That’s a bit of a confusing statement. So, here’s a description of what I actually did with the colors.
•    The Ha and OIII emission lines were separated from the continuum spectrum and mapped to approximate true colors.
•    Hbeta was estimated to have an intensity of 37% that of Ha in each pixel and mapped to its approximate true color.
•    The image was color calibrated using PCC in PixInsight.
•    Adjustments in Topaz and PI emphasized the colors and details present in the image.
•    An L-channel was synthesized from intermediate HO and HORGB CIELAB  L* components.

As for the nebula itself, at the center of these discarded gas shells sits the massive O-type star that formed the inner bipolar nebula. Earlier episode(s) of shell-shedding produced the outer nebular shell and perhaps the blue shell around the red, inner shell. Massive stars, such as this, do not live long. This one probably has about two million years left before it ends, most likely, in a supernova explosion.

For non-obvious reasons, each of the two lobes of the inner (red) nebula has a separate designation: NGC 6164 lies to the north (upward) with NGC toward the south (downward).

Comments welcomed!
Alex Woronow