NGC  3981: A Twisted Spiral

OTA: ASA RC1000AZ f/6.8
Camera: FLI PL9000
Observatory: Telescope Live, Chile

EXPOSURES:                
R: 16 x 1200 sec
G: 14 x 1200
B: 17 x 1200
L: 19 x 1200
Total exposure:    22h processed out of 32h40m of purchased exposures

Processed by Alex Woronow (2022) using PixInsight, SWT, Topaz

It is a shame that I reckoned that only 2/3 of the images were usable since I paid for them all, but SubframeSelector and my Subframe Weighting Tool deemed it so. All frames, used and discarded, had a dead column down the center of the subs, and worse, maybe a dozen more rows adjoining that one had diminished signal! Not Good!

Oh, another thing: all the RGB were 2x2 binned…in my opinion, that is a waste of potential information. Half as many 1x1 frames in the 1200s would have added sufficient color and provided extra detail in their contribution to luminosity. Furthermore, some images overlapped almost not at all. The vignetting is way beyond ordinary, and to boot, it is an alt-az mount, so the stars have spikes in every which direction (but that’s to be expected). What a shame that a data set from a 1m telescope was so fraught with problems!

BTW-1: ESO published a capture of this galaxy and said the capture was not for research but was done in the telescope's free time for public outreach. There’s not much I could find about the history of this twisted galaxy…it is in the Virgo group, so it has plenty of opportunities for encounters with other galaxies!

BTW-2: Telescope Live posted a tutorial by A. Block (with additional issues recognized) that remediates this image's problems. I did not follow his remediation methods but addressed the problems my way.

Nonetheless, after much remediation, I am relatively pleased with the result of a lot of generally unnecessary work. Still, I won't be framing this one!

Astronomy.net plate solution:
Center (RA, Dec):    (179.020, -19.896)
Center (RA, hms):    11h 56m 04.736s
Center (Dec, dms):    -19° 53' 45.676"
Size:    15.6 x 15.6 arcmin
Radius:    0.184 deg
Pixel scale:    0.274 arcsec/pixel