NGC 3981: Grace from Chaos (Alex Woronow)

Celestial hemisphere: Southern · Constellation: Crater (Crt) · Contains: NGC 3981 · PGC 3094231 · PGC 37384 · PGC 37562 · PGC 37566 · PGC 846906 · PGC 849071

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NGC 3981: Grace from Chaos

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NGC 3981: Grace from Chaos

NGC 3981: Grace from Chaos
(a.k.a. Arp 289)

OTA: CDK17 f/6.8
Camera: QHY 600
Observatory: Deep Sky West
Date of Capture: Jan, '23
Date of Processing: Nov, 23

Exposures:
R: 27 x 300 sec
G: 27 x 300
B: 28 x 300
L: 50 x 300
Total Exposure time: 22 hours
Image Width: 33.4 arc-minutes

Processing Tools:
1.   Commercial: PixInsight, Topaz (Studio2, Photo AI2), Photo Director 365, Aurora HDR, GraXpert
2.   Pixinsight Addons: NoiseXTerminator, BlurXTerminator, StarXTerminator, Normalize Scale Gradient
3.   My Scripts: NB_Assistant, AC_Restar, Subframe Weighting Tool (Excel w/ J. Hunt), ColorTweaker

Target Description:
Other than the obvious, NGC 3981 has had a near encounter with some other galaxy (hence its splayed geometry); not much is written about this object.

Processing Description:
Processing is most challenging when the thing you want to see is just above image noise, and that was the case here. Despite a high-quality data set, in terms of consistent low noise level and consistent sky quality (as judged from image star abundances), there was a color gradient, red to green, across the image. Attempts to suppress such a gradient always seem to leave behind a somewhat mottled background that is difficult to suppress without taking along faint signals. This image is my first attempt at using GraXpert AI background removal. It did about as good a job as I have seen. However, the resulting image's mean-average deviation (largely due to variations in the background intensities) was still about twice what PI's Dynamic Background Extraction yielded.

Statistics:
Distance: 52M ly
Apparent Magnitude: 11.8
Pixel Span at Target: 90 Trillion km

Alex Woronow

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Distribution of astrophotographers

This table shows the number of distinct astrophotographers who have been assigned and IOTD/TP award compared to the total number of images awarded.
	Distinct awarded users	Total awarded images
Image of the day
Top picks
Top pick nominations

Distribution of subject types

This table shows the distribution of awards per subject type, compared to the popularity of images of that subject type.
	Image of the day	Top pick	Top pick nominations	Total submitted
Deep sky
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Extremely wide field
Star trails
Northern lights
Noctilucent clouds
Landscape

Distribution of data sources

This table shows the distribution of awards per data source, compared to the popularity of images acquired from that data source.
	Image of the day	Top pick	Top pick nominations	Total submitted
Backyard
Traveller
Own remote observatory
Amateur hosting facility
Public amaeteur data
Professional, scientific grade data
Mix of multiple sources
Other
Unknown

The “AstroBin Image of the Day and Top Picks”, or IOTD/TP, is a long-running system to promote beautiful, interesting, peculiar, or otherwise amazing astrophotographs, with a focus on technical excellence. Learn more.

Submitted The date and time when you submitted this image for IOTD/TP consideration.	...
Views by Submitters (available since September 19th, 2023) Every image is assigned to 50% of available Submitters. In the event that at least 80% of them don't view the image before its time in the IOTD/TP process expires, it's assigned to the other 50% of Submitters and the process begins anew.
Promotions by Submitters When 3 distinct Submitters promote the image, it moves on to the next stage of the process: evaluation for Top Pick status. This requirement, in addition to anonymization of images and distribution to only a subset of them, prevents biases and ensures that the best images are selected.
Promotions by Reviewers When 3 distinct Reviewers promote the image, it moves on to the next stage of the process: evaluation for IOTD status.
Early dismissal Staff members have a lot of images to inspect on a daily basis, and they can dismiss images if they believe they don't meet the requirements for IOTD/TP selection. If an image is dismissed 5 times, it's removed from the process. This streamlines the process and ensures that any bias present in promotions could be overruled by other staff members.

Status	Advanced success
Started	...
Astrometry.net job	8835897
PixInsight job	W166TAT5MRN68DXE3SUNCZM2IPD3KMQC
PixInsight queue size	n/a
PixInsight stage	TASK_LOG

RA (center)	11h56m04s.390
RA (top/left)	11h57m15s.255
RA (top/right)	11h54m53s.646
RA (bottom/right)	11h54m53s.286
RA (bottom/left)	11h57m15s.420

Dec (center)	-19°53′23″.50
Dec (top/left)	-19°42′51″.100
Dec (top/right)	-19°42′52″.30
Dec (bottom/right)	-20°03′54″.79
Dec (bottom/left)	-20°03′52″.71

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NGC 3981: Grace from Chaos

NGC 3981: Grace from Chaos

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NGC 3981: Grace from Chaos

NGC 3981: Grace from Chaos

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