M31 Andromeda Galaxy in HaLRGB with Esprit 80 / ASI1600MM / MyT (Rowland Archer)

M31 Andromeda Galaxy in HaLRGB with Esprit 80 / ASI1600MM / MyT

Not exactly first light, but early light (first month) with my Skywatcher Esprit 80, which I picked up during the recent sale, specifically to go after wide fields objects like M31 without mosaics and with some room to spare. I needed it as my R frames were a bit shifted and I had to crop out the stacking artifacts.

I start getting saturation with only 8 seconds of L, so I shot a relatively large number of L frames - 600. Mr. Moon contributed some light to the situation but I was eager to see some results with the new setup so soldiered on. Due to meridian flips and imaging across several nights, I found my integrated subs had some gradients coming in from both the top right and bottom left corners, requiring a couple of passes with PixInsight's DBE process and careful selection of samples to clear things up. My first attempts at DBE were of the "more the merrier" philosophy, but after listening to Warren Keller's talk at the recent AIC, I think the "less is more" approach works better. PixInsight is starting to feel like less of a black box to me - I'm starting to develop a mental model of what the process does. So for DBE, I'm not just shotgunning samples all over the image, but trying to look at the big picture and "outline" the start and finish of the major gradients, plus a couple of interior points. Takes less time and works better.

I wanted to selectively add the Ha data to point out the star-forming regions in the spiral arms, so I used a mask to target them during a PixelMath add to the R channel. I first tried a mask that included the galactic core but it made everything a bit too red for my taste.

C&C always welcome!

Clear skies,

Rowland

9 hours of integration:

L = 600 x 8 sec

R = 134 x 60 sec

G = 104 x 60 sec

B = 104 x 60 sec

H = 30 x 240 sec

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Status	Advanced success
Started	...
Astrometry.net job	1801812
PixInsight job	SCMOI9AU7HLH2XGNBSI28CNJK0Y47BWG
PixInsight queue size	n/a
PixInsight stage	TASK_LOG

RA (center)	00h42m46s.10
RA (top/left)	00h46m55s.42
RA (top/right)	00h35m19s.13
RA (bottom/right)	00h38m46s.10
RA (bottom/left)	00h50m07s.76

Dec (center)	+41°16′51″.8
Dec (top/left)	+42°30′10″.2
Dec (top/right)	+41°39′25″.5
Dec (bottom/right)	+40°03′02″.9
Dec (bottom/left)	+40°52′29″.1

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