Casitas de Gila, Gila, New Mexico
March 31, April 1 - 4, 2022

Reprocessed 2/7/2023

I made my Spring trip to a dark sky site in New Mexico with galaxy season in all its glory (Spring break from the clouds and rain in Oregon).  For all imaging, I used my Celestron 9.25” SCT at prime focus (FL = 2350mm, f/10).  There were so many galaxies to pick from, and to take advantage of the fairly long nights, I imaged three targets each night primarily waiting for Virgo and Coma Berenices to get to optimal positions in the sky.  M104 was the second target where I captured about four hours of data over several nights using Luminance, Red, Green, and Blue filters.  I captured all data with 4 minute exposures.  Only the brightest stars were clipped, but the galaxy core was preserved.  However, the results were disappointing with limited sharpness and lousy stars.  Was it the conditions or me?  Yes!

While atmospheric conditions were predicted to be average or better, there was enough variation in transparency, seeing, and sometimes wind, that guiding and subframe quality were well below my expectations.  There were at least two nights where the Jet Stream passed directly overhead as the weather patterns were highly variable.  I had not used the telescope without a focal reducer for almost a year and I had become used to improved guiding in PHD2 using the multi-star guide option.  It was also difficult to find more than one guide star around the galaxy.  Guiding performance varied from 0.6 to 1 arc-min.  Even in New Mexico, M104 proved a challenge as it remained fairly low in the sky.  Also, the temperature dropped between 30 and 40 degrees Fahrenheit, so the auto focus routine ran often and had difficulties with so few stars in the field of view.  Another learning was that strong winds during the day battering my Telegizmo 365 cover moved the mount and hardware by about 1 to 2 arc minutes, so I used the Polemaster camera with SharpCap Pro V4 each evening to fine tune the polar alignment.  Other astrophotographers and I also suffered from several AC power outages, one human caused and the others from a prickly GFCI.

Original Version Processing:

I continued to have success with the NormalizeScaleGradient script applied to the aligned subframes.  I tried and tried to create starless images of the luminance and RGB color images in the linear state with StarXTerminator (AI version 10) and StarNet2 in PixInsight.  StarXTerminator removed part of the galaxy core while StarNet2 left too many artifacts.  For NGC 3184, I had to stretch the image first, then apply StarXTerminator.  I then finished stretching the starless and stars images before combining into a LRGB image.  Both tools still have issues with galaxies, especially in the core region.  Stretching images was done with different tools using a try and apply approach.  A combination of GenerisedHyperbolicStretch, HistogramTransformation and CurvesTransformation tools were employed in a non-reproducible way.

Reprocessing 2023:

I continued my effort to reprocess most of the image data sets that had flaws and issues using new PixInsight tools and an improved workflow.  Again, Russ Croman’s XTerminator tools made a significant difference in improving the imaging and simplifying the workflow.

Description:

M104, the Sombrero Galaxy, is a spiral galaxy in Virgo.  It has a very bright nucleus, a massive dust ring, and a very large and bright halo giving it its “Mexican hat” shape.  There is a supermassive black hole in the core of about 1 million solar masses.  It is estimated that the mass of M104 is 800 billion suns, one of the largest galaxies in the Virgo supercluster.  M104 is a type Sa spiral, it is about 29 Mly from Earth, and it has a diameter of about 130 kly (NASA and SkySafari Pro).

Imaging details:

Celestron 9.25" Edge HD SCT (FL = 2350mm, f/10)
Celestron off-axis guider with a ZWO ASI 174MM mini guide camera
Losmandy G11 mount with Gemini 2
ZWO ASI 2600MM Pro cooled monochrome camera (-10C)
ZWO 36mm Luminance, Red, Green, and Blue filters
Equatorial camera rotation: 340 degrees

Software:    Sequence Generator Pro, ASTAP plate solving, PHD2 guiding, 
    Losmandy Gemini ASCOM mount control and web client interface,
    SharpCap Pro for polar alignment with the Polemaster camera,
    PixInsight 1.8.9-1 with R. Croman XTerminator tools,
    Photoshop CC 2022/2023

Luminance    4 min x 64 subframes (256 min), Gain 100, Offset 68, 1x1 binning
Red        4 min x 22 subframes (88 min), Gain 100, Offset 68, 1x1 binning
Green    4 min x 28 subframes (96 min), Gain 100, Offset 68, 1x1 binning
Blue.      4 min x 28 subframes (96 min), Gain 100, Offset 68, 1x1 binning

Total integration time: 8.9 hours