Looking for Advice on Improving M31 - Forums

Topic starter

Sep 13, 2023

Hi folks:

It's that time of year again, and I'm wondering whether or not to try and improve upon my M31. In 2021, I imaged it with my DSLR & APO Doublet, in 2022 I combined that data with new data taken with an L-Pro filter but was a little disappointed in the relatively modest improvement. Specifically, I felt it was lacking in fine detail.

This year I have the same setup, but I've moved from a Skyguider Pro to a CEM26. My guiding error was < 2" with the Skyguider, and is now < 1" with the CEM26 so that may help. My exposure length with the L-Pro is 120s, but I'm wondering if I should try shortening the exposures to improve detail. Alternatively, perhaps I should ditch the L-Pro and take much shorter exposures with a UV/IR cut filter, but I do live in a Bortle 7 zone so maybe that's a bad idea.

They say that insanity is doing the same thing over and over again and expecting different results, but perhaps this is simply a matter of gathering more of the same type of data and reaping the benefits of stacking & drizzling. Perhaps, though, I should be rethinking my acquisition process.

Thoughts? I'm not looking for suggestions on upgrading my gear (save for the possible purchase of a UV/IR cut filter) as I cannot afford anything new right now. Likewise, I'm unable to travel to a dark site either. Any other ideas are welcome!

CS and thanks in advance!
Mark

M31 - Andromeda (2021)

M31 - Andromeda (2022)

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andrea tasselli

Frequent contributor

Sep 13, 2023

I'm afraid that with a 61mm refractor (and a doublet at that) the margin of improvements aren't that great. Your stars look especially wonky so again unless you change your gear that isn't very likely to improve the results. And avoid drizzle (unless it is CFA drizzle, if you're using PI and if you don't then think about getting it). Color and rendition aren't bad so at least you should get some improvement by keep using the L-Pro and add more data to it. I see no gain whatsoever in reducing the length of the exposure if your guiding is stable.

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enta

Sep 14, 2023

I feel like 120s is quite long for a F5.9, not sure how much impact the L-Pro has.
I just finished my M31 using 30s. subs @ F7.5 without a filter, but I do live in B4/5, so I guess the L-Pro is necessary.
Your pic doesn't look overexposed so I guess shorter subs are not of any value.
With your setup you got a arcsec per pixel value of 2.46", so if you're consistently tracking beyond 1" I'm wondering why your stars are not perfectly round.

Other than that I assume you're limited to your equipment and seeing conditions.
A dedicated cooled astrocamera could improve the result quite a bit.

I only got around 40min. of exposure per panel with 30s subs, no filter ony myrecent attempt

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Mark Germani

Topic starter

Nov 7, 2023

Hi folks:

Thanks for the feedback. I re-evaluated my approach, and realized I'd been including a lot of subs in the stack from previous years, before I was guiding or had any filters. I opted to cull pretty aggressively, and added 12 hours of RGB (L-Pro) and 12 hours of Ha (L-eXtreme). It's hard to ditch data when we get so few clear nights, but I think it helped.

M31 Andromeda Galaxy in HaRGB (2023)

I have quite a bit of CA with my Z61, and maybe I'm wrong but I think imaging when M31 is closer to 45 degrees rather than zenith might not be helping in this regard. I also have a tilt issue with my Z61 which my local telescope repair shop is unable to resolve.

I'm looking into a dedicated camera for next year's go at this target. Thanks again for the advice!

CS,
Mark

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