The Andromeda Galaxy Messier 31 (Barry Wilson)

The Andromeda Galaxy Messier 31

In mid-summer Steve and I began considering the next project for our FSQ106/QSI683 rig in Spain and we both quickly alighted on a study of Messier 31 our nearby galactic neighbour in Andromeda. We both wanted a deep image and after framing the four panel mosaic we realised that this project would be a 100hr+ undertaking and would span many weeks. We captured the first frames on the 1st July and finished the final frames on 13th October. As well as the subs for each panel we also acquired shorter luminance subs for the central regions to boost fine detail.

The calibration and assembly took a few days whenever I could spare the time and the processing took most of a day one wet Sunday. There were some stubborn gradients, to be expected given the timescale over the data collection period, and I know we were maximising capture time on each panel over successive lunar phases and I'm sure we had periods clashing with some moonlight. Nonetheless, PixInsight worked its magic and the mosaic came together. I have posted up the full FOV of the four panel mosaic (excepting stacking artefacts) and also a slight crop to remove the bright blue star at the top of the frame to remove any distraction from the galaxy.

From Wikipedia: "The Andromeda Galaxy (IPA: /ænˈdrɒmɪdə/), also known as Messier 31[color=#c9c9c9], [/color]M31, or NGC 224 and originally the Andromeda Nebula (see below), is a barred spiral galaxy approximately 2.5 million light-years (770 kiloparsecs) from Earth and the nearest large galaxy to the Milky Way[color=#c9c9c9].[/color][6] The galaxy's name stems from the area of Earth's sky in which it appears, the constellation of Andromeda, which itself is named after the Ethiopian (or Phoenician) princess who was the wife of Perseus in Greek mythology.The virial mass of the Andromeda Galaxy is of the same order of magnitude as that of the Milky Way, at 1 trillion solar masses (2.0×1042 kilograms). The mass of either galaxy is difficult to estimate with any accuracy, but it was long thought that the Andromeda Galaxy is more massive than the Milky Way by a margin of some 25% to 50%. This has been called into question by a 2018 study that cited a lower estimate on the mass of the Andromeda Galaxy,[10] combined with preliminary reports on a 2019 study estimating a higher mass of the Milky Way.[11][12] The Andromeda Galaxy has a diameter of about 220,000 ly (67 kpc), making it the largest member of the Local Group in terms of extension.The number of stars contained in the Andromeda Galaxy is estimated at one trillion (1×1012), or roughly twice the number estimated for the Milky Way.[13][color=#c9c9c9][[/color]needs update]The Milky Way and Andromeda galaxies are expected to collide in around 4-5 billion years,[14] merging to form a giant elliptical galaxy [15] or a large lenticular galaxy[color=#c9c9c9].[/color][16] With an apparent magnitude of 3.4, the Andromeda Galaxy is among the brightest of the Messier objects[color=#c9c9c9],[/color][17] making it visible to the naked eye from Earth on moonless nights,[18] even when viewed from areas with moderate light pollution."

One of our goals was to capture the fainter outer halo and I have presented the galaxy in my usual "naturalistic" style and it is plainly evident; I could stretch the data further but I don't want to risk over processing nor creating an artificial brightness to the dim halo. Despite 7 hours of Ha data there was limited evidence in the Ha data of any hydrogen gas cloud proximate to the galaxy in the rig's FOV. Maybe I could really push the background but I have chosen not to spoil the natural processing. The outer spiral structure readily displayed the blue hues after calibration. I have tried to keep the Ha regions muted so as to not dominate.

Data acquisition: Barry Wilson & Steve Milne
Processing: Barry Wilson

Original
B
C
Final
D

B

Description: Slight crop to frame to concentrate on the galaxy

Uploaded: ...

C

Description: Amended colour balance

Uploaded: ...

D

Description: Amended colour balance - crop

Uploaded: ...

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Status	Advanced success
Started	...
Astrometry.net job	5160040
PixInsight job	DZH4GEE7E9QCOQIHF9Z50YR6LFYPXTHX
PixInsight queue size	n/a
PixInsight stage	TASK_LOG

RA (center)	00h42m48s.84
RA (top/left)	00h49m22s.45
RA (top/right)	00h49m33s.33
RA (bottom/right)	00h35m52s.61
RA (bottom/left)	00h36m24s.51

Dec (center)	+41°19′27″.9
Dec (top/left)	+39°37′41″.5
Dec (top/right)	+43°01′22″.8
Dec (bottom/right)	+43°00′02″.10
Dec (bottom/left)	+39°36′20″.5

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