M63 Sunflower Galaxy

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oopfan
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M63 Sunflower Galaxy

Post by oopfan »

It took three nights to capture but should have only taken two. My 50-year-old mount is "acting up". Time for its annual DIY HyperTune: strip it down, soak the gears in de-greaser, lube it up, and re-assemble. This is its last photo before going into dry-dock:
M63_W12-90x90s-b1_R-64x90s-b1_G-28x90s-b1_2021-04-06_oopfan.jpg
M63_W12-90x90s-b1_R-64x90s-b1_G-28x90s-b1_2021-04-06_oopfan.jpg (336.88 KiB) Viewed 93 times
Technicals:
William Optics 71mm f/5.9
Atik 314E

Wratten #12: 90x90s bin1, SNR: 5.93
Red: 64x90s bin1, SNR: 2.72
Green: 28x90s bin1, SNR: 2.73
Total SNR: 7.07
Total Integration Time: 4.55 hours

Processing:
Astro Pixel Processor (APP): calibration, registration, integration, color combine, background calibration, star color calibration, selective color (cyan->blue, yellow->red).
Affinity Photo: de-noise, contrast, highlights, black level, crop.
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Menno555
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Re: M63 Sunflower Galaxy

Post by Menno555 »

Nice. I like the color setting in it.

Menno
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oopfan
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Re: M63 Sunflower Galaxy

Post by oopfan »

Thanks, Menno.

I have two computers: a laptop running Ubuntu where I run APP, and a desktop where I run Affinity Photo. The laptop's monitor is "warm" and the desktop's monitor is "cold". I tried but I can't calibrate them to a single standard. So, the final step is iterative. I make small changes with Affinity, and then copy the file to the laptop. I try to find a happy medium.

Brian
timh
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Re: M63 Sunflower Galaxy

Post by timh »

That is quite detailed - I think that you are getting the best out of that 71 mm Brian,

Btw when you specify those SNR values which part of the image is it in respect of --or is it some kind of average?

best wishes
Tim
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oopfan
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Re: M63 Sunflower Galaxy

Post by oopfan »

Hi Tim,

I'm glad you asked: "is it some kind of average?" I've been wanting to dedicate a paragraph to that topic, but never got around to it.

Referring to the attached annotated image, there is a governing body that decides the dimensions of the ellipse. They take into account the extent of the galactic halo. Once they agree on that, then they calculate the integrated magnitude. They do this by capturing the galaxy with a Photometric "V" filter (light green), and then accumulating the pixel values within the body of the ellipse. I assume they exclude foreground stars. So in the case of M63, all of those pixels add up to an equivalent star of magnitude 8.6V. Given those three values (magnitude, major and minor axis) we can calculate the Surface Brightness.

Surface Brightness of 22.12 requires a lot of integration time with my scope and Bortle 5 skies. Depending on your monitor, you can see that I have just begun to capture the halo, but there is a lot more there. My image has a Total SNR of 7.07 (based on 22.12 surface brightness and 20.02 skies). It took 4.5 hours to capture. It is an OK photo, but I would need SNR 20+ to win an award at AstroBin. My small aperture stands in the way, as well as my camera's low max QE of 54%, and the use of a Wratten #12 filter (minus blue) for luminance.

To answer your question, yes it is the average brightness within the ellipse.

Brian
Attachments
M63_surface-brightness.jpg
M63_surface-brightness.jpg (468.96 KiB) Viewed 76 times
timh
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Re: M63 Sunflower Galaxy

Post by timh »

Thanks Brian. That is a very good explanation and I'm tempted to try it. In principle you wouldn't need the whole ellipse to make comparisons but I would imagine just at defined positions wthin the margins? It does potentially provide a quantitative basis for astro-imaging :-) as a competitive sport but I think that Bortle 6 puts me out of the running. Maybe on holiday -- by far my deepest image of M31 was taken at Bortle 3-4.
TimH
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