m101 color issue

Questions and answers about processing in StarTools and how to accomplish certain tasks.

m101 color issue

Postby singding » Wed Apr 18, 2018 1:43 pm

Hi!

I recently did m51 HaLRGB and I thought I got great colors, but for some reason, having trouble with m101.Away, can I get some assistance? I tried synthetic lum and synthetic chrominance, (rgb only in chrominance) but galaxy is kind of one color...
I will google drive the files, anu help is highly appreciated!

I used astro pixel processor to stack, and as far as I know, I used the simplest methods, no local normalization(lnc) or mbb during stacking, as I know ST likes data likes this.
I know ST is great, but there are tools that I think i just simply dont know how to use right :(
I auto dev- wipe- auto dev- decon- sharp- contrast- hdr- life-then life again on isolate- colors- stop track and noise reduce is my normal workflow, I think masking is my biggest issue, along with colors.

I was under assumption when masks are turned off, the unmasked portion remains the same...no? on life isolate preset video on youtube (I just saw it so haven't done it myself yet) it appears a mask was set on veil, but when processing was complete the unmasked area was darker.. can you explain?
sorry to bug you again Ivo :)

Adam

Ha- https://drive.google.com/open?id=101uzQ ... UknwbHPnk6
lum- https://drive.google.com/open?id=1atqie ... A1fkViugl2
red- https://drive.google.com/open?id=1whf3T ... T9Cb0jHJ3T
green - https://drive.google.com/open?id=1YYvfC ... HHhkoyHi1Q
blue- https://drive.google.com/open?id=1xZ9zx ... _uOyO9uoCr
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Re: m101 color issue

Postby admin » Thu Apr 19, 2018 7:07 am

No worries Adam!

Can you give me exposure times for the 5 stacks? I can't do the weighting without it... :)
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Re: m101 color issue

Postby singding » Thu Apr 19, 2018 10:12 pm

Sure!
Ha 8820 seconds

Lum 8730
Red 6270
Green 8460
Blue 12105

Thanks Ivo :)
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Re: m101 color issue

Postby admin » Sat Apr 21, 2018 3:09 am

Hi Adam,

I just had an attempt at processing this, but there are a number of issues that keep me from achieving anything useful.

By far, the biggest issue is that the Ha stack is extraordinarily noisy. It almost seems to be a single very short exposure sub, rather than 8820 seconds worth of data. What exposure times did you use? They may have been to short to capture much signal?

The other stacks are poorly (not or not at all?) calibrated with flats, while they suffer from walking noise as well (as if they weren't dithered properly).

I am going to give you some tough love right now - please don't take this the wrong way;

Stop what you're doing. You need to work on you acquisition and calibration skills before you delve into HaLRGB compositing. Learn to walk before you start running. Pick a single band (say, Ha or L) and learn the ropes, max out what you can acquire in a single band, then start augmenting that detail with other bands when you're ready.

Trying to capture and accentuate faint nebulosity using Ha is futile if your data isn't calibrated properly and if you don't dither properly. All up, you've spent 44385 seconds, 740 minutes, over 12 hours acquiring data that is borderline usable, because it hasn't been calibrated properly, hasn't been dithered properly and is - for reasons I'd love to investigate with you - very, very noisy.

Take a modest approach, take it back to basics. You (near!) future self will thank you! I'm here to help.
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Re: m101 color issue

Postby singding » Sat Apr 21, 2018 3:47 pm

Oy Ivo! I will never go back to basics lol. I have gotten some pretty decent images, but I think I didn't go deep enough on Ha for some reason. ( 3 min subs at gain 200. I dither every 2 frames for a high dither. I just changed to very high dither spiral to see if it helps on my next 2 images.

Thanks for looking at it. I was able to get decent results (minus walking noise) on APP, and I know ST is capable, I just feel I am doing something wrong. I will attempt to process without Ha. I also used gain 0 on LRGB, and I have that horizontal/vertical lines pattern which I got before on gain 0. I think I will go back go gain 76 on the ASI 1600.

Anyway, I am attempting to use ST without Ha and I will post my result. Here it the APP version (noise reduction in ST only)

thanks Ivo ( still curious to see what I can do w/ ST on this data :) )



Adam
Attachments
m101final.jpg
m101final.jpg (304.51 KiB) Viewed 336 times
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Re: m101 color issue

Postby admin » Sun Apr 22, 2018 1:35 am

No worries Adam - the last thing I want is for you to get frustrated with the hobby. It's meant to be fun and rewarding.
Don't get me wrong - inundating yourself with new gear, tools, software, techniques, etc. is of course a totally valid approach if you don't mind the "herding cats"-esque learning curve. :D

I normally add Ha to the synthetic luminance, as adding Ha to the red channel skews coloring. Doing it it that way simply accentuates areas with Ha by increasing their brightness, rather than skewing their color.

In this case the Ha data was very noisy, while the red channel (which was meant to capture the coloring of the Ha areas) had the least amount of exposure time. E.g. it's the worst possible case for using the aforementioned technique.

The alternative then is to add the Ha to the red channel, and make its presenc known that way. It will obviously skew coloring in those areas.

The below is the result of processing a synthetic luminance (weighted R+G+B+L) and synthetic color data;

adam_crop_proc.jpg
adam_crop_proc.jpg (207.73 KiB) Viewed 331 times


To create the synthetic color data, I used Screen in the Layer module made a 65/35 screened blend of R (background) and Ha (foreground). I saved the result and imported this as the R in the LRGB module, and loaded G and B as-is. I then very lightly processed the resulting synthetic color data.

This was then composited (I used the Layer module, see elsewhere) with a processed version of the the synthetic luminance data to arrive at the image above.
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Re: m101 color issue

Postby singding » Sun Apr 22, 2018 1:59 am

:)

I knew there was a pretty picture in there ;)

You are the best! I will try to see if I can replicate it somehow.
So getting more red is a valid approach? I like the image! Good job and thank you Ivo, you are always super helpful :)

Adam
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Re: m101 color issue

Postby admin » Sun Apr 22, 2018 2:38 am

singding wrote::)

I knew there was a pretty picture in there ;)

You are the best! I will try to see if I can replicate it somehow.
So getting more red is a valid approach? I like the image! Good job and thank you Ivo, you are always super helpful :)

Adam


Get more of *everything* is always a good idea... :P

Getting good Ha + good red will allow you to add the Ha to synthetic luminance and make it stand out in "correct" visual-spectrum coloring.
The Ha in the synthetic luminance is more likely to bring out detail in areas where the red channel is dominant (since we humans see pure Ha emissions as red) - that's why having good red signal is important if you go that route. Ha detail may correlate with other colors as well though, such as the usual pink/purple H II regions. Pink/purple has a blue component, so some TLC for your blue data is also recommended.

That said, staying in the visual spectrum for your coloring is a decision that is totally up to you. There are a million different ways to integrate narrow band. All valid.
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Re: m101 color issue

Postby singding » Sun Apr 22, 2018 8:18 pm

Do you happen to recall how you blended the processed synthetic luminance with the chrominance in layer module? There are a million ways, just wondering how you managed it .
I did my synthetic Lum and chrominance with red, green and blue (res being Ha and red layered with screen mode) and am now trying to figure out the last part.

Thanks!

Adam
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Re: m101 color issue

Postby admin » Wed Apr 25, 2018 11:08 pm

singding wrote:Do you happen to recall how you blended the processed synthetic luminance with the chrominance in layer module? There are a million ways, just wondering how you managed it .
I did my synthetic Lum and chrominance with red, green and blue (res being Ha and red layered with screen mode) and am now trying to figure out the last part.

Thanks!

Adam


See Combining Luminance and RGB images using the Layer module here.
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