Another M31

[WolfieGlos]

I actually wanted to focus on M78 in Orion this winter, and I started collecting data on it on 14th November. But as Orion was out of view until beyond midnight at the time (because of my stupid house being in the way! I have to wait until it's broadly south-east), I spent the first hours of that night collecting data on M31. I had no intention of imaging it this year, but it was visible, high above me and required no changing of filters so it seemed reasonable to go for.

I last imaged this just over a year ago with my Evostar 72ED, this year I got closer in with the Starfield 102ED and so I intended to gather a lot of data to try and make a real good go of this understandably popular target.

After collecting nearly 5 hours of data on that first night; exactly 1 month ago, I've only been able to collect 3.5 hours since for a total of 8.5 hours. To be fair, 8.5 hours on M31 produced a decent image, but I wanted the fainter outer bands so I decided to try combining with the 06:45 hours that I captured last year with the 72ED for a total of 15 hours! 

So here is the result. With what seems to be perma cloud cover for the coming weeks - and the coming Moon phase - I think I'll call this one done. Fairly happy with this, but for such a bright target in some ways I feel like I was expecting more for 15 hours of integration 🤷‍♂️

170 x 180s with 102ED and 102 x 240s with 72ED, all ISO-400 with Canon 800Da. Stacked in ASTAP, processed in Siril / Starnet / Topaz / GIMP. Very minor star reduction outside of the galaxy; none within.

 

EDIT: HaRGB version added

 

Edited December 30, 2023 by WolfieGlos
HaRGB version added

[Sarek]

That's really great Chris! What a result.

Was it hard to combine data from the different FOV's? I hadn't thought of trying that.

[tomato]

That’s a great M31, I think the colour balance is spot on. I have a version with a similar integration time and like you I somehow thought the galaxy would be more prominent but as has been said before this subject is a lot trickier to image than people might expect.

[WolfieGlos]

6 hours ago, Sarek said:

That's really great Chris! What a result.

Was it hard to combine data from the different FOV's? I hadn't thought of trying that.

Thank you Sarek!

Actually no, it wasn't hard to combine! For each of the 3 nights with the 102ED, I stacked them individually in ASTAP so the flat correction worked correctly. I then had 1 full stack of the 72ED from a year ago, stacked with Siril - both at the same ISO and using the same DSLR, and luckily, a similar rotation.

I took those 4 stacks, and stacked them together in Siril (using an OSC with no DBF script) to stack them without calibrations. That was it. Nothing fancy! I wanted to see if it would work first of all, and I was pleasantly surprised at the result. I guess I may have lost some resolution using different focal lengths (570 vs 420), so in an ideal world I would gather more time with the 102ED and then compare.

The only problem that I had which I didn't mention above, was that the 72ED suffered from some quite severe tilt which meant the combined stack duplicated stars in the corners - see below. So I removed them with Starnet and then added in the stars from a stack of the 3x stacks of 102ED data, so actually the stars in my image are "only" 8.5 hours worth of data. By eye, I couldn't tell any difference elsewhere in the image in the stars, but some tiny background galaxies have lost some data by doing this....not that I can resolve them anyway.

6 hours ago, tomato said:

That’s a great M31, I think the colour balance is spot on. I have a version with a similar integration time and like you I somehow thought the galaxy would be more prominent but as has been said before this subject is a lot trickier to image than people might expect.

Thanks tomato! I'm pleased you say that about the colour balance, I really struggled to get a result I liked with the colour. I think this was the 5th or 6th iteration, some were too blue, others too orange, or using Siril's PCC....brown. Yuck. I made a post on this a year ago trying to get colour in M33 if you recall, so I'm pleased you say that 🙂

Agreed on M31 being trickier than some may think, despite it being a "big beginners target", getting a good processed result I found to be more difficult than I had expected.

[WolfieGlos]

With some clear skies (finally) to cap off the year, it of course was paired with the near Full Moon tonight. Usually I go for star clusters in this situation but I decided against that and managed to add some Ha data to this image, captured just over 2.5 hours with the l'enhance tonight.

I've never combined Ha with RGB data previously so this was a new learning curve (thanks @ONIKKINEN for your post which came up on a Google search - used the 50/50 blend with R and Ha 🙂 ) , happy with the result and seem to have achieved a better contrast in the arms this time. Definitely something to explore and practise with going forwards.