NGC 3521: Fuzzy on the Outside, Turbulent on the Inside

OTA: CDK 24
Camera: Moravian 61000Pro
Observatory: Heaven's Mirror
Date of Capture: May '23
Date of Processing: May '24

Exposures Used:
R: 21 x 900 sec
G: 19 x  "
B: 21 x  "
H: 32 x  " (3x gain)
Total Exposure time: 21.5 hours
Image Width" 22' 10"

Processing Tools:
1.    Commercial: PixInsight, Topaz, Radiant Photo
2.    Pixinsight Addons: NoiseXTerminator, BlurXTerminator, StarXTerminator, GraXpert
3.    My Scripts: NB_Assistant, AC_Restar, Subframe Weighting Tool (Excel w/ J. Hunt), ColorTweaker, StarTweaker

Target Description:
Sean Liang provides the following description in a Sky and Telescope gallery:

"NGC 3521 is a spiral galaxy 40 million light-years away in the constellation of Leo. It belongs to a class of galaxies known as flocculent spirals. Unlike galaxies with well-defined spiral arms, this galaxy has many small, patchy spiral arms, giving it a woolly appearance. Remarkably, this galaxy is enshrouded by a gigantic bubble-like shell. The shell is made of debris and star streams that once belonged to small satellite galaxies. They were torn apart by tidal forces and devoured by NGC3521 (this process is vividly called "galactic cannibalism"). The remaining became the ghostly shell."

Processing Description:
There was very sufficient H,R,G,B data, so the L was discarded to keep from degrading the image resolution. Extracting the abundant detail present in this galaxy takes time and effort. The halo of gas and stars softens our view of the galaxy's disk. The trick is to obtain the disk's detail while retaining the halo…without masking if possible. (Masking can leave artificial contrast boundaries that I try to avoid.) This image did not use masking, and the disk and the halo appear accurately.

Usually, I use SXT to remove stars, but in this case, it left quite a few stars behind and pulled small objects, perhaps stars, out of the galaxy. I found that SN2 had neither of these problems. So….


Target Statistics:
Distance: 26.2M ly
Apparent Magnitude: 11
Pixel Resolution: 0.39"
Pixel Span at Target: 4.7E13 km

Alex Woronow