m31 reprocess

[Bluesboystig]

I have finally managed to re-process 3h of integration time on m31 from the autumn, and I'm quite happy with the improvement, as I contained the noise and managed to get good (for me at least) details. Not 100% sure about the colours, any feedback?

Acquisition: 70x180s, 10 darks, 20 flats, 20 biases, ISO 800, Bortle 5

Equipment: Star Adventurer GTI, WO z61 with Flat 61, Canon 2000d modded, Optolong L-Pro, AsiAir mini, ZWO mini guidescope and Asi 120mm guide camera. 

Processing all done in Siril: stacking, crop, background extraction as much as possible (there is still some gradient that I can't seem to be able to remove), starnett ++ for star removal, generalised hyperbolic stretch. Noise removal done with Topaz Denoise.

Happy to hear comments/tips.

Cheers

[TiffsAndAstro]

Much nicer than the one hour I got last night. Maybe a tad orangey?

Did you try photometric colour calibration in siril?

Looking closer, your image is even more  much much nicer than mine. Your core is so much less blown out than mine and you also have more detail throughout. And 3x longer subs than me...I only done a quick preview stretch on mine.

I'll try get another hour on it tonight if lucky.

Edited Monday at 13:32 by TiffsAndAstro

[Bluesboystig]

I did, and it completely kills all the colour, it comes out really really flat and white, and weirdly also for some reason the final image has much more noise as well. I used the Human Weighted Luminance colour model in the GHT in Siril to get some colour out while stretching (the even weighted luminance model was even more orangey). What I like of this version is that there is a fair amount of detail without too much noise. The goal when capturing was to get one of those epic images full of blue, with hints of red etc. No idea how to get that though, I thought 3h would give me enough to work with but clearly I still have plenty to learn (and understand).

[TiffsAndAstro]

20 minutes ago, Bluesboystig said:

I did, and it completely kills all the colour, it comes out really really flat and white, and weirdly also for some reason the final image has much more noise as well. I used the Human Weighted Luminance colour model in the GHT in Siril to get some colour out while stretching (the even weighted luminance model was even more orangey). What I like of this version is that there is a fair amount of detail without too much noise. The goal when capturing was to get one of those epic images full of blue, with hints of red etc. No idea how to get that though, I thought 3h would give me enough to work with but clearly I still have plenty to learn (and understand).

Er, your image is really not far off epic as far as I'm concerned. If you're looking for red blobs, that's usually from hydrogen alpha emissions via a filter added back in.

With a modded dslr you might have to extract it via siril script then composite it back in to taste as a luminance channel via siril? I'm fairly new so bare that in mind ;(

Also galaxies seems to be portrayed as mostly white/blue more than yellow. But I don't know if that is a choice or reality, see my own attempt few months ago

 

[TiffsAndAstro]

Maybe just try the colour saturation in siril? 

[Bluesboystig]

2 minutes ago, TiffsAndAstro said:

Maybe just try the colour saturation in siril? 

Thanks, definitely worth a try! I really like your images by the way, plenty of nice detail in there!

[TiffsAndAstro]

3 minutes ago, Bluesboystig said:

Thanks, definitely worth a try! I really like your images by the way, plenty of nice detail in there!

Lol that's very kind of you to say but they're rubbish. I only show you to see how same image can look different after processing and at the time I wasn't trying to make them different "hues" (?).

[Bluesboystig]

19 minutes ago, TiffsAndAstro said:

Lol that's very kind of you to say but they're rubbish. I only show you to see how same image can look different after processing and at the time I wasn't trying to make them different "hues" (?).

They do look good to me, I honestly like a lot all that internal structure, they look really nice!

[Bluesboystig]

A little bit of tinkering and this is another version, trying different ways to get better colours.. more noise in exchange for better colours?

[TiffsAndAstro]

47 minutes ago, Bluesboystig said:

A little bit of tinkering and this is another version, trying different ways to get better colours.. more noise in exchange for better colours?

personally, i like this a lot. it looks 'real' whatever real is

[carastro]

The first version was too Orange, but the second version is good.  Considering this is from a DSLR is is remarkably noise free.  What's your secret? 

Edited Monday at 16:04 by carastro

[Bluesboystig]

43 minutes ago, carastro said:

The first version was too Orange, but the second version is good.  Considering this is from a DSLR is is remarkably noise free.  What's your secret? 

Ha thanks so much! A little friend called Topaz Denoise I suppose? But I also try hard not to overdo it with the stretching, I guess I’m losing out on some data but at least I think I’m managing to keep that noise under wraps a little..

[ollypenrice]

I think the colour is much better in the second but that there is way too much indiscriminate noise reduction in both. The first thing I see when I look at these images is... noise reduction. I see that before I see M31.

By 'indiscriminate NR' I mean NR applied where it isn't needed. Also applied beyond what is needed. I would urge you to leave a little grain in the image and to apply NR only to parts of the image which need it. Beware of the 'vaseline on the lens' look. Use NR where you need it and sharpening where yu can but, in neither case, apply either universally.

It's very, very rare that I feel an imager has left the black point too high since black clipping is such a temptation. However, in this case, I think the black point might come in a point or two.

I say all this because the image is very good, not because it isn't.

Olly

[Bluesboystig]

32 minutes ago, ollypenrice said:

I think the colour is much better in the second but that there is way too much indiscriminate noise reduction in both. The first thing I see when I look at these images is... noise reduction. I see that before I see M31.

By 'indiscriminate NR' I mean NR applied where it isn't needed. Also applied beyond what is needed. I would urge you to leave a little grain in the image and to apply NR only to parts of the image which need it. Beware of the 'vaseline on the lens' look. Use NR where you need it and sharpening where yu can but, in neither case, apply either universally.

It's very, very rare that I feel an imager has left the black point too high since black clipping is such a temptation. However, in this case, I think the black point might come in a point or two.

I say all this because the image is very good, not because it isn't.

Olly

Thanks so much for the feedback, I really appreciate it. The point of me sharing this images is to learn, definitely not to brag (not much to brag about in the first place anyway), so thanks for taking the time to look and share your thoughts. Using Siril and Topaz Denoise I’m not sure I can apply sharpening and denoising selectively, what I can do is check how much noise there is before firing TD. I guess it’s about compromising at this stage. And regarding the blackpoint, I stopped bringing it in when I saw I started clipping data, even though it was just 0.001%.. maybe I was too “protective”? I’ll keep playing around with this data and try different things. Thanks again for the feedback!

[WolfieGlos]

Yeah, I have to agree with Olly on the noise front. Colour is much better in the second image, it just needs less NR and more subs to compensate I’d say. 

As a comparison, This is my version I captured last year also with a DSLR, also processed in Siril and Topaz. I’m not saying it’s perfect by any means, but I always struggled with colour balance in Siril, even using PCC , and often my galaxies came out brown and orange like you had. In the end I stacked with different software (ASTAP) for broadband targets and the colour came out much better. Don’t ask me why! 

However I think it can be compensated in Siril a bit now with Asinh and careful GHS stretches using the modified Asinh stretch option, but in all honesty, since going to Pixinsight, I’ve struggled with colour a lot less than before thanks to SPCC. I think it’s due to be incorporated into Siril soon. I might take your approach and give my M31 a rehash when I get some time 🙂

[Bluesboystig]

4 minutes ago, WolfieGlos said:

Yeah, I have to agree with Olly on the noise front. Colour is much better in the second image, it just needs less NR and more subs to compensate I’d say. 

As a comparison, This is my version I captured last year also with a DSLR, also processed in Siril and Topaz. I’m not saying it’s perfect by any means, but I always struggled with colour balance in Siril, even using PCC , and often my galaxies came out brown and orange like you had. In the end I stacked with different software (ASTAP) for broadband targets and the colour came out much better. Don’t ask me why! 

However I think it can be compensated in Siril a bit now with Asinh and careful GHS stretches using the modified Asinh stretch option, but in all honesty, since going to Pixinsight, I’ve struggled with colour a lot less than before thanks to SPCC. I think it’s due to be incorporated into Siril soon. I might take your approach and give my M31 a rehash when I get some time 🙂

That's a hell of a shot there! Love the blue and orange combination! 15h of integration time look like the money shot for me, but I guess the more the better?! I thought for a super bright target like m31 3h would be enough to get decent details, but I was definitely wrong. I think the problem here is that to get the details out I need to stretch the hell out of the data, and that brings out an awful amount of noise. More integration time, more patience, and more restrain. This hobby is a lesson in self management! 

Thank you so much for the feedback, much appreciated!

[WolfieGlos]

Thanks 🙂 I suppose we’re always critical of our own work and there’s things I don’t like about it, but I only pumped in the time to try and reduce noise and get the fainter details in the outer areas. You’ve got a nice image as it is, the blue is nice, but it’s just possibly stretched and noise reduced a tad too far. Maybe try adding some more of the reduced stars back too, it might help to mask some of those effects.

[TiffsAndAstro]

Also it's a bad time of year for M31 as it's low down. 

My image was a quick test to see if it really exists. I'll do hopefully 10 hours osc on it later in year when it's higher and darker.

[ollypenrice]

14 hours ago, Bluesboystig said:

Using Siril and Topaz Denoise I’m not sure I can apply sharpening and denoising selectively, 

It is absolutely vital to be able to apply any and every processing operation selectively. This lies right at the heart of image processing and is sometimes called 'the zone system.'  Once you can do this, you're off. There are two systems which are used widely, layering or masking, though they are in some ways the same thing.

I use Photoshop layers but a quick glance at GIMP, the free alternative, shows that the method I use is available in GIMP. It is simplicity itself with a real time preview of results.

- Create two layers by pasting the original on top of the modified (eg noise reduced) version.

- Use the Colour Select option in the Selection Tools to select, by colour, the regions that want the most NR. You do this by moving the cursor over them. The software will throw an outline around what you've selected. If it looks like what you wanted, keep it. If not try again. You can now expand and feather your selection so that its boundaries will be gradual and invisible at the end.

- Use the eraser to remove the top layer within your selection and reveal the modified bottom layer. You can do this in iterations by making the eraser only partially effective (set it to 20% or 50% etc). Alternatively you can erase at 100% and then go to Edit-Eraser and backtrack the eraser effectiveness to any percentage you like. Just look at the image to see what you like.

- Flatten the image (ie blend the layers as you see them now in layers.)

You can do the same process after altering colour saturation, after sharpening etc., so you only get the modification where you want it.

Olly

PS Purists will tell me off for erasing directly rather than through and black and while transparency mask but I've never felt the need to use a mask for this.

Edited Tuesday at 08:09 by ollypenrice
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