(I have edited the posted images. The "original" "final" LRGB image is actually Version 4, which was made from synthetic L comprising L, R, G and B integrated frames, which have themselves now been integrated together. I was able to increase the L SNR by doing this. ColorCalibration was done using the entire image as the white reference.)

The weather finally cleared after almost 5 solid months of rain, clouds and misery! I was beginning to despair that I would never image another galaxy again.

Image List

This is M63 with the following "revisions":

A ("Original" and "Final") - LRGB Version 4 from Synthetic L

D - LRGB Version 1

E - LRGB Version 2

F - LRGB Version 3

G - Synthetic L

H - Inverted L

I - Annotated L

Imaging Session Accomplishments

I was able to image M63 over 7 nights during which time I experimented with the following:

1) Varying exposure times for later HDR combination (not presented here yet)

2) Imaging of G2V stars for color calibration (several versions shown here)

3) Refining polar alignment through PHD2 (out of practice for 5 months!)

4) Optimizing PHD2 autoguiding parameters (for ONAG and local conditions)

5) Remeshing the mount, recording the updated PEC curve

6) Evaluating the CCD for future tilt correction (parts on order)

Notes

I have three versions here in which I experimented with ColorCalibration in PixInsight. Your comments and criticisms are welcome. I think I like Version 3 the best. Version 1 turned out a little too vibrant, and I lost some of the hard-earned detail. Version 2 is interesting, but I think it's too blue. Your suggestions on the colors and processing are very welcome.

(The following is more information than you may want to know, but I'm using this Description field for my personal notes. Feel free to skip over the rest.)

M63 is a famous galaxy that needs no further introduction here. It has become my favorite bright galaxy given its beautiful flocculent ("having or resembling tufts of wool") texture, elegant presentation (orientation) and view, and its interesting surrounding features. I had time to go deeper in the details and was able to capture some of the surrounding "nebulosity" of the galaxy despite imaging from my suburban backyard. Luckily the clouds parted during the time of the new moon, which is a rare occurrence for me outside of the summer months.

The images here are all from 600s frames. The brighter stars are, of course, completely washed out, particularly after the stretch, but I was able to play with ColorCalibration during the linear steps on many of the stars that weren't yet pegged out in RGB.

I also took a series of 15, 30 and 60s frames with which I am experimenting with HDRComposition in PixInsight, however I am finding processing the combined images somewhat difficult as the usual default settings for Deconvolution, MLT and other processes need to be adjusted accordingly. I will return to it later and will experiment with performing the HDRComposition step at different points in the processing chain.

Here are the PixInsight processing steps applied to these images:

L, R, G, B Steps

Calibration

SubframeSelector (Having many frames allowed me to be pickier than usual)

Registration

ImageIntegration

DrizzleIntegration

Geometry Adjustment (crop, 180o rotation, mirror flip due to ONAG)

Further L Steps

(linear)

DynamicBackgroundExtraction (DBE - 2 stages: few points wide, more points narrow)

Deconvolution (with mask, star mask, DynamicPSF)

MultiscaleLinearTransform (MLT - background noise reduction)

(nonlinear)

Stretch (taking several smaller steps turned out better than one big step)

CurvesTransformation (again taking several steps)

Stretch (tried to find an adequate final black level)

MLT (another pass seemed required, although this did soften the background elements)

RGB Steps

(linear)

ChannelCombination

ColorCalibration (more on this later)

DBE (again 2 stages)

MLT

(nonlinear)

Stretch

CurvesTransformation

SCNR (removed the usual greenish tinge form the background)

MLT (again this smoothed out the background noise but at the expense of more softening)

Stretch (attempted to set an honest black level)

LRGB Steps

ChannelExtraction (separated the L, a and b channels from the final RGB image)

ChannelCombination (combined a and b with the final processed Luminance L)

Additional Steps on L

ImageSolve (Jon Rista introduced me to this - thanks, Jon!)

ImageAnnotation (I notice that some of the little surrounding galaxies weren't labeled)

Invert Image

Notes on ColorCalibration

I spent some time imaging a particular G2V star nearby in order to calibrate the R, G, B frames in a more systematic manner, however this didn't work out well. I took 15, 30 and 60s frames and found that the ratio of intensities of the three colors varied with exposure. I was probably not capturing the light in a linear portion of the CCD's bit range. I'll need to read up more on this and ask questions.

I settled on making the usual white and black references from the M63 RGB image itself using stars whose color indexes seemed close to that of G2V stars. This is how I did Versions 1 and 2. For Version 3 I used the bright center of the galaxy as my white reference. The result was a much more bluish color, which, although I find pretty, doesn't seem as natural.