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M31 Andromeda Galaxy
Posted By: blues_hawk, 11-28-2019, 10:39 AM

M31, Andromeda Galaxy is actually quite large in the night sky. It juuust fits in my 600mm aps-c frame.
This one is a noise reduction "stack" of 5 images of 900 seconds each.
Post Proccess in Siril, gimp, and Rawtherapee.



Last edited by blues_hawk; 11-28-2019 at 11:05 PM.
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11-29-2019, 07:32 PM - 1 Like   #16
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I never get tired of viewing the awe and mystery of Andromeda. The colored shot above is one of my all time favorites. Thanks for posting it.

11-29-2019, 11:11 PM - 1 Like   #17
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love this, great work, interesting processing
11-30-2019, 09:50 AM   #18
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QuoteOriginally posted by Apet-Sure Quote
I never get tired of viewing the awe and mystery of Andromeda. The colored shot above is one of my all time favorites. Thanks for posting it.
Isn't it interesting? Thing is, that's what colors my K5's bayer sensor saw. Using what I am coining SLE or Super Long Exposure, brought out more subtle details and color than I had seen in previous shorter exposures and stacks. I usually have to subtract some "green noise" that often shows up as a haze if you leave it in when you calibrate/equalize the colors in histogram.
I did do one really tricky thing on this particular image. I saved Red green and blue as separate images, then re-composited(combined) them using the one with the most detail(blue in this case) as a luminosity value in order to add detail and bring out those dark gas lanes.
11-30-2019, 09:58 AM   #19
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There is always room for improvement so to critique my own images, this one and the m42 also recently posted, short focal ratio newtonians all suffer from a horrible coma and I have to use a lens called a coma corrector to flatten the field enough to get round stars. As a result there is some fringing and CA in the stars, but far less than my achromat scopes produce. I also see some sensor tilt which could be caused by collimation, but may also be caused by the slip fit at the focuser. The F4 newtonian is very picky about collimation but it tends to show up similar to coma, and since the larger stars are still round I feel this case is likely caused by an off kilter camera. I plan to tap and add add thumbscrews to the focuser sleeve to allow me to fix that. Another issue I see is the pesky dotting I get when I upload an otherwise smooth image and the websites re-compress it. I have a tendency to tease out background gas and end up with noisy images, which I choose to keep rather than raising the black level to hide the noise and lose the background.

11-30-2019, 06:06 PM - 1 Like   #20
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QuoteOriginally posted by blues_hawk Quote
Another issue I see is the pesky dotting I get when I upload an otherwise smooth image and the websites re-compress it.
I always save my jpegs at 100 quality setting. I noticed that this was dropping to 85 when I posted them here on PF. I found out that if I keep the posted images at 1200x800 pixels or less, the jpeg quality stays at 100. As the dimensions go up, the website turns the quality down.
11-30-2019, 11:10 PM   #21
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QuoteOriginally posted by Apet-Sure Quote
I always save my jpegs at 100 quality setting. I noticed that this was dropping to 85 when I posted them here on PF. I found out that if I keep the posted images at 1200x800 pixels or less, the jpeg quality stays at 100. As the dimensions go up, the website turns the quality down.
Awesome! That's probably exactly it. I'll make that adjustment, thanks!
12-02-2019, 03:33 PM   #22
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What are your thoughts of black and white film for this?
12-05-2019, 08:34 AM   #23
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QuoteOriginally posted by jeffh Quote
What are your thoughts of black and white film for this?
There used to be special high rate films for use in astrophotography(ap), but they were meant to make shorter exposures work. If you had the rest of the rig already running long sub arc second tracking I bet you could do some interesting shots with film.

We soemtimes use narrow band filters, originally used to narrow down the light spectrum to make spectral analysis of particular mineral types easier but now the filters are used to get around light pollution. The output from them is usually stored in luminosity frames only(bw), but because there is no color dispersion--known in photography as CA or chromatic aberration, those images are often super sharp. --I bet film would work terrific behind an HA filter, as long as it's special film strong in IR reception as H-alpha operates in really deep red. -- I wonder how an O-iii would do? That's in the spectrum color film would pick up. onder:

It's all speculation on my part of course. My last film camera was a Kodak Disc. :P

12-05-2019, 09:13 AM   #24
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Beautiful;, you guys are making me want to do astro.
12-05-2019, 11:01 AM   #25
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QuoteOriginally posted by Archimedes the Dog Quote
Beautiful;, you guys are making me want to do astro.
Thank you!
AP has gotten much more approachable in recent years but don't jump in without research and or a tutor. It can be a huge money pit.
12-05-2019, 11:23 AM   #26
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Well done. This requires a lot of patience and skill.
12-05-2019, 11:27 AM   #27
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QuoteOriginally posted by GRB Quote
Well done. This requires a lot of patience and skill.
Thanks! It's been a long road to this point. About 5 years of active development, building and learning a ton of stuff. I could name about half my junk "frustrating" and it would answer....some of it would respond by coughing up some part I just fed it. But I'm still excited anytime I have time and good sky for it, which isn't all that often where I am.
12-05-2019, 01:15 PM   #28
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QuoteOriginally posted by blues_hawk Quote
Quick followup: While I was fixing the link to this one I spotted one you might like in my album I used a 50-200mm ed lens to do this one. Could use a flat but I thought you might to see it anyway. I piggybacked the camera and lens earlier in the season and just let it shoot what the main rig was pointing at.
Both me and my daughter are interested in trying this. This forum has relieved some of her stress about trying, and failing. Our first attempts with a k1000 we found at a thrift store almost made her not want to go any further. we did manage to get a vivitar 75-205 lens for her camera pretty cheap. hopefully she see Photos like this and decides to stick with it.
12-05-2019, 02:59 PM   #29
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Wow amazing shots! thanks for sharing!
12-05-2019, 03:04 PM   #30
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Wow, you manage to fill a APS-C frame with Andromeda with a 600mm lens? Really? I would have never believed it. Thanks for sharing.
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