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NGC 4731, 4731A, and IC 3812



Scope: Celestron 9.25 Edge HD 235 mm at f/7, Location: DAA Observatory, Shelter Valley, CA,   20 April 2023  Camera: ASI294MM (Baader  LRGB Filters)

Exposure: Luminance - 72 x 3 minutes (gain-121 2x2) ,  R - 48 x 2 minutes  - (gain-121 2x2), B - 24 x 2 minutes  - (gain-121 2x2).

Processing: Data Collection -  Sequence Generator Pro (as FITs).  Sub-frame calibration - Pixinsight (WBPP). Sub-frame  registration and integration (Average combine -  Winsorized  Clipping Rejection) - PixInsight (WBPP).  Mure Denoise - PixInsight.  Non-linear stretching - PixInsight. Gradient Correction - PixInsight.  Curves, Levels, RGB combine, Luminance layering - PixInsight. Generation of starless Luminance image for later processing - StarXTerminator. Photometric RGB calibration (SPCC) - PixInsight.  De-convolution - BlurXTerminator.  Final finishing  - Affinity Photo.  Annotation - PixInsight, Aladin (Simbad and NED), and Affinity Photo. This image is a  LRGB with luminance layering.  Image processed at 8092x5444 resolution. Final Image size is approximately 4807x3234.

North is to the left in this image. NGC4731 is the dominant galaxy in this image - it is a Seyfert 2 galaxy, classed SB(s) cd. Its distance is 84 million light years by redshift estimate (40 mly by independent Tully-Fisher estimate). Its smaller companion galaxy to the right is NGC 4731A (also known as Holmberg 472B) - also a Seyfert 2, distance of 85 million light years by redshift estimate and classed Im pec. Smaller galaxies in the upper right are IC 3812, LEDA 1029635, LEDA 1029569 (top down). IC 3812's distance is estimated at 172 million light years (by redshift). There are many background galaxies in this image that are best seen in the full size image.  There are three Quasar candidates in this image (as seen on the annotated image) - all of which are somewhat "average" redshift  (light travel time or Lookback up to 9.154 billion years, redshift up to 1.400). These objects, information,  and some of the brighter stars are identified in the annotated image  Horizontal FOV is approximately 39.4 arc minutes. Full size image scale is approximately 0.492 arcsec/pix..  

Image center is approximately - Equatorial 2000: RA: 12h 50m 40s Dec: -0631'11" 



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