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M63 Sunflower Galaxy


WolfieGlos

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Clear skies lately have been in abundance, with no Moon...but typically running out of Astro-dark time (!)

This is one of those galaxies I wanted to have a go at. I was going to stop after circa 7 hours, but I managed to get the faint tidal stream so pursued with the target to try and capture the stream. It appears in an Inverted Histogram view, but to stretch the image to show it, it's just a mass of noise. It's *just* visible in my final image if you look closely, but I suspect I might have to more than double the 12 hours I have to really bring it out, and with the loss of astro dark in the UK, I might have to shelve that for now.

I'm quite pleased with the result despite the modest focal length (570 with reducer) giving this a nice widefield view. Despite Siril's plate solver only recognising M63 in the frame, I've found the widefield view is home to a lot of faint fuzzies, Stellarium tells me they are in the PGC and UGC catalogues, and are littered around this field. There are also some very distant and possibly large galaxy clusters, one just above-left (by the 2 bright stars) and one towards the bottom right corner. Sadly I can't locate any names for the clusters. There's also a faint-ish object just to the left of the very top-middle, at first I thought it was an artifact. But it appears to be a galaxy or possibly a jet or some kind? I can't locate an object name or number, but I think I'll call it the ball-bag 🤣

For this image, I've also discovered ASTAP for stacking, and it produced a MUCH more colourful result than Siril. I've noticed with galaxies that Siril tends to make them brown, example below showing it. I don't know if its the Canon RAW files it doesn't like, but this might be the reason I struggled with M33 earlier in the year, for those who remember and kindly helped me on that. Has anyone else experienced this with Siril? Anyway, I think I will be using ASTAP for galaxies going forwards.

Starfield 102 + 0.8 reducer + Canon 800D (modded) + HEQ5.

144x 300s lights at ISO-400. 6x darks, 50 bias, 40 flats.

Stacked in ASTAP, processed in Siril and GIMP. Comments welcome 🙂

107d-20-05-23-M63SunflowerGalaxy.thumb.jpg.52ce1c1a8ebe013e2c610e3ed36959ad.jpg

Cropped image:

107d-20-05-23-M63SunflowerGalaxyCrop.thumb.jpg.52934718f959b7328ac8a3e257c02631.jpg

Tidal stream *just* visible in the histogram-negative view, looks a bit like devils horns. I'm sure the RASA owners would nail this !

M63_Tidal_Stream.png.6364d8f049117c01ff5758fb8f4204b6.png

And here's a version stacked in Siril....notice the brown shade to the galaxy and total lack of blue in the galaxy. This is apparent in the final stacked image when you open it, and then during processing with or without PCC.

107c-16-05-23-M63SunflowerGalaxy.thumb.jpg.e59965a1de52f8ba1c8ce4d1f0f406ea.jpg

Edited by WolfieGlos
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That's a great image.

Thinking about what you said about Siril, you might have a point. I always thought it may have been an issue with my camera sensors but a lot of my images I wondered why there was a lack of blue in the starfield as the vast majority like over 90pc were all yellow, surely there can't be regions in space which selectively only have yellowish stars showing up across the whole sensor? Your images above seems to show the same issue. Even after photometric colour calibration the issue persists in mine, also when I use it PCC it alters the blue colour in targets making them more green/cyan. 

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Great result!👍

Colour on galaxies is really strange, when SPCC came out for Pixinsight I thought great, a scientific, quantitative assignment of colour using a 215 million star database, no more hassle getting the colour right. However, in practice it gives a strange result about 30% of the time. Then it is back to csc in Astro Pixel Processor, or me adjusting the channels based on reference photographs.

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4 hours ago, Roy Foreman said:

Very nice image despite the short focal length and great star colours. Well done.

Thank you Roy !

3 hours ago, Red Chilli said:

Outstanding work

Many thanks 🙂

3 hours ago, Elp said:

That's a great image.

Thinking about what you said about Siril, you might have a point. I always thought it may have been an issue with my camera sensors but a lot of my images I wondered why there was a lack of blue in the starfield as the vast majority like over 90pc were all yellow, surely there can't be regions in space which selectively only have yellowish stars showing up across the whole sensor? Your images above seems to show the same issue. Even after photometric colour calibration the issue persists in mine, also when I use it PCC it alters the blue colour in targets making them more green/cyan. 

Thanks Elp! Interesting you say that, as this is probably the most colourful Starfield I’ve ever produced! It had a saturation boost of 1.2 in GIMP (applied to the whole image after stretching), but that was it. I’d always assumed my lack of a colourful Starfield was due to the modified camera, or simply that’s how it is.

2 hours ago, tomato said:

Great result!👍

Colour on galaxies is really strange, when SPCC came out for Pixinsight I thought great, a scientific, quantitative assignment of colour using a 215 million star database, no more hassle getting the colour right. However, in practice it gives a strange result about 30% of the time. Then it is back to csc in Astro Pixel Processor, or me adjusting the channels based on reference photographs.

Thanks Tomato 🙂

Just picking up on the Siril stacking you both mentioned and brown galaxies, it’s strange and I also thought that auto colour calibration would be great! The reason I tried Astap was following a google search after getting frustrated with M63 and the obviously wrong colour, and I came across this thread on the developers forums: https://discuss.pixls.us/t/m31-andromeda-why-is-siril-making-it-appear-mauve-brown/20934

Although its from a few years ago, clearly the problem persists. I haven’t tried a manual colour calibration like was suggested to be fair. I did try temperature adjustment in gimp, but the whole image was a lot colder.

Ive never noticed a lack of blue previously, whether that be stars (might have been my 72ed’s blue fringing hiding the problem…) or in reflection nebulae like M45. On that basis I assumed it was fine for galaxies. If I take an unprocessed stack from Siril, open it in gimp and process, it’s very much the same result so it must be in the stacking, or possibly when it converts RAW to fits? 

The moment I opened the stack from Astap, it was clear it had the colour we associate with galaxies. 

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I've just had a go at trying to bring out more of the tidal stream.

The data is there, it's just bring it out, and I think it is noise limited from my data. I boosted it with a GHS in Siril, then I ran it through AstrodeNoisePY trying several options and that really lost some of the star quality when zoomed in. Overlaying the noise-reduced version in GIMP on a Darken Only layer seems to have helped a bit. Some of the stars seem a bit bloated now though 🤷‍♂️

M632023-05-17144x300LEOS800D_150911_stacked-4a-border_rev-a_siril-dn1-gimp.thumb.jpg.3b86be8b1e22c92d2e74c71b8a9df948.jpg

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I've had one final go, removed the additional GHS stretch I put in earlier and found a better noise reduction technique. Managed to bring out the stream a bit more. Much happier with this version.

 

107e - 20-05-23 - M63 Sunflower Galaxy.jpg

107ec - 20-05-23 - M63 Sunflower Galaxy Crop.jpg

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