Pinwheel Galaxy, M101 (jewzaam)

Pinwheel Galaxy, M101

Pinwheel Galaxy (M101) and it's neighbors. And there are MANY more than I thought in the field! Turning on annotations for quasars and small galaxies (see revision) I count 177 small galaxies (green) and 144 quasars (purple)! And I know some of the slightly larger (but still small) galaxies didn't get marked. I did remove markings for anything that wasn't visible in the final image. But also some are quite faint, I'm counting everything I can! Can you blame me?

This was my first attempt at an LHaRGB image. It took me many attempts and a few months of ignoring the project to finally nail down a way to process that I liked.

The tricky things for me in processing this were 1) how to combine L with Ha for a composite L, 2) the combination of Ha into RGB, and 3) good definition of the spiral arms without clipping.

To create a composite L I stretched both L and Ha and combined with a simple PixelMath expression to take the max of each. This seemed to give the best result of retaining the Ha in LRGBCombination and not loosing the faint bits of the spiral arm brought in by L.

For Ha combination I had been using NBRGBCombination. But for this I found the EmissionLineIntegration script to work very well. I just played around with the amount for Ha, dropping it from the default a bit, until I found a pleasing amount of red for the Ha regions. I did BackgroundNormization after that to bring the background back to an acceptable balance.

And for the spiral arms I found I could get them to pop easily with moving the black point in HistogramTransformation but it ended up looking harsh and clipped. This was about the time I got frustrated with the data set and put it down for a few months. In that time I started using curves with an inverted luminance mask to bring down the background. It has served well in this and other pictures I have processed and is my go-to for reducing background brightness now.

Original
J
L
Final
M

J

Title: Annotated

Description: Green + is small galaxies (count = 177).
Purple + is quasars (count = 144).

Uploaded: ...

M

Description: Trying new things with stretching, HDRMT, and final manipulations.

Uploaded: ...

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Status	Advanced success
Started	...
Astrometry.net job	7630532
PixInsight job	6ZV76KYTEWSTBFQKP36WC1TEH2Y3QKF9
PixInsight queue size	n/a
PixInsight stage	TASK_LOG

RA (center)	14h03m33s.886
RA (top/left)	14h00m02s.273
RA (top/right)	14h00m05s.440
RA (bottom/right)	14h06m56s.888
RA (bottom/left)	14h07m09s.913

Dec (center)	+54°21′56″.97
Dec (top/left)	+55°08′22″.93
Dec (top/right)	+53°35′38″.76
Dec (bottom/right)	+53°35′08″.76
Dec (bottom/left)	+55°07′55″.80

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