Casitas de Gila, Gila, New Mexico
April 4 - 6, 2022

Reprocessed 2/7/2023

Original:

During my Spring trip to a dark sky site in New Mexico, I was looking forward to imaging NGC 4651, the Umbrella Galaxy.  As the second target in the nightly imaging session, I used my Celestron 9.25” SCT at prime focus (FL = 2350mm, f/10) with Luminance, Red, Green, and Blue filters.  For each filter, 4 minute exposures were taken.  I was not pleased with the final result as the galaxy structure is not sharp and the colors are not quite right.  As with other targets imaged during this trip, atmospheric conditions were variable, with some periods of degraded transparency or seeing.  I need more luminance data to bring out more detail and make the umbrella-shaped tidal tail more distinct. 

Reprocessed 2023:

I continued my effort to reprocess most of the image data sets that had serious 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.  I was not able to obtain a better color mix in the core of the galaxy.  Successive masking and the application of the CurvesTransformation tool got me close.  Also, I cropped the final image to offset the galaxy and include the small galaxies in the lower left corner.

Description:

NGC 4651, the Umbrella galaxy, is a small spiral of type Sc in the constellation Coma Berenices.  The faint “umbrella” is actually tidal stream of stars stripped from a small satellite galaxy that was absorbed by the larger spiral. The umbrella appears to extend some 100 thousand light-years above the galaxy's bright disk. A small galaxy was likely torn apart by repeated encounters as it swept back and forth on eccentric orbits through NGC 4651.  The remaining stars will join the larger galaxy over the next few million years. Thus, this galaxy is a good example of the power of the gravity of a massive object to perform a galaxy acquisition.  NGC 4651 is about 76 Mly from Earth and has a diameter of 85 kly.  The light from this galaxy was emitted when dinosaurs ruled the Earth (Wikipedia, 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 Russ Corman’s XTerminator tools
    Photoshop CC 2022/2023

Luminance    4 min x 52 subframes (208 min), Gain 100, Offset 68, 1x1 binning
Red     4 min x 26 subframes (104 min), Gain 100, Offset 68, 1x1 binning
Green    4 min x 28 subframes (112 min), Gain 100, Offset 68, 1x1 binning
Blue    4 min x 26 subframes (104 min), Gain 100, Offset 68, 1x1 binning

Total integration time: 8.8 hours