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m31 is fun and big!

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#1 bakernyc

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Posted 19 January 2021 - 08:51 AM

Hey all. Out last night with some sketchy seeing trying my first round on m31. I didn't realize how big it was when I started (particularly after mars as my first and only astrophotography experience). So here's the middle-ish of it. 127 Nexstar SLT, EOS 550d, 30x30sec @1600 iso, a couple darks for noise, DSS stacked, post processing in GMP.

So I think I really need to look at post processing. I really didn't know what I was doing in GMP but I was able to get some good signal, although also a good amount of noise when I stretch it far enough to get some of the body of it. Anyways any advice is necessary. Given I don't want to switch up equipment maybe I'll try m33 next. Any advice for post processing images in GMP is helpful.

 

 

 

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#2 zakry3323

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Posted 19 January 2021 - 09:01 AM

Looks great! M31 can be a tough one to process because the center bulge is so much brighter than the arms. I don't have any specific Gimp advice- but if you can use masks, they will help a lot! Another strategy could be shooting at two exposures- use the short stack and process for the core and stars, and the long stack for the arms and dust lanes, then combine.  


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#3 jonnybravo0311

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Posted 19 January 2021 - 09:38 AM

Good start... what will really help you is a LOT more data. You've got a total of 15 minutes. You need _hours_ of integration time. Examples from my own data...

 

10 minutes:
M31 10 minutes
 
10 hours:
M31 7Nights

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#4 Gipht

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Posted 19 January 2021 - 09:43 AM

I like Gimp for putting the final touches on the picture, but find it difficult to use for the initial stretching of the picture. Software like Star Tools and many others handle that process better and easier.  Astro Pixel Processor offers a trial version, or at least they  did, for free and would be worth a try for you.


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#5 bakernyc

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Posted 19 January 2021 - 09:48 AM

Hey Zak - thanks for the advice on using different exposures and then combining? What would be a tactic to do that combination? Obviously need a bigger field of view as well - I think I can put a .5x reducer on there with the same scope and get almost the right size.


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#6 jonnybravo0311

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Posted 19 January 2021 - 09:59 AM

Hey Zak - thanks for the advice on using different exposures and then combining? What would be a tactic to do that combination? Obviously need a bigger field of view as well - I think I can put a .5x reducer on there with the same scope and get almost the right size.

That's a bit of an advanced tactic... basically you take two sets of data. One set you deliberately use shorter-than-normal exposures. You are purposefully underexposing the majority of the image in order to preserve details in the extremely bright areas (i.e. Andromeda's core, Orion's Trapezium, etc). The other set of data is your normally exposed set.

 

In post processing, you would combine the two images using HDR blending techniques.


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#7 MeenSeen

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Posted 19 January 2021 - 10:02 AM

 

Good start... what will really help you is a LOT more data. You've got a total of 15 minutes. You need _hours_ of integration time. Examples from my own data...

 

10 minutes:
 
 
10 hours:

 

Honestly, I find you 10 minute version to have more impact emotionally for me.  Very ethereal IMHO.


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#8 jonnybravo0311

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Posted 19 January 2021 - 10:29 AM

Honestly, I find you 10 minute version to have more impact emotionally for me.  Very ethereal IMHO.

I'll be honest... when I originally did the "10 minute vs 10 hour" exercise, I wasn't expecting to get nearly the amount of detail from the data as I did. Sure, it's extremely noisy, but I was shocked.

 

I'm going to target Andromeda again with the new scope. Right now I've been collecting data on M81... because I thought it fitting to do M81 with my GT81. I got another 3 hours last night. There are a few more clear nights forecast for this week, and with the increasing moonlight, pointing my scope north seems the better choice :)



#9 zakry3323

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Posted 19 January 2021 - 11:04 AM

Hey Zak - thanks for the advice on using different exposures and then combining? What would be a tactic to do that combination? Obviously need a bigger field of view as well - I think I can put a .5x reducer on there with the same scope and get almost the right size.

I'm sorry, I can't be much help with the processing aspect for you, I've only used Pixinsight, and to a lesser (and less successful) extent PS for combining images. Jonnybravo's explanation for the data acquisition aspect is the same as what I'd suggest. Different cameras, different optics, different skies, so you won't end up with the same settings as me, but on a slower scope like your Mak, I'd probably start with around 20 seconds at ISO 1600 (or a little longer at ISO 800 for less noise- but again, we have different cameras- mine is unacceptably noisy at 1600) for stars and the core, and for faint details shoot as long as you can track well. 

 

Make sure you do plenty of research and talk to folks who have reduced their Maks before investing in the reducer. The field is already corrected on a Mak, so you'll want to be getting a reducer that doesn't also flatten, or your resulting images will end up over-corrected.  


Edited by zakry3323, 19 January 2021 - 11:30 AM.

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#10 bakernyc

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Posted 19 January 2021 - 01:46 PM

Grabbed star tools and followed the standard workflow. Amazing how much detail is hidden here. Can't wait to get a wider perspective. Thank you for all the replies.

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