M101 feedback

[Pitch Black Skies]

Hi guys,

Could I get a bit of feedback please?

I feel my pictures look heavily processed and unrealistic. This is an example of M101.

It is 19hrs fully calibrated. I use DSS to stack and Startools to post process. I think Startools is the culprit, however I am only using each module once and never increase their parameters.

[alacant]

Hi

If you like, post a link to the file. Then we may be able to advise better.

StarTools allows you to go as heavy or as light as you wish. My guess is that you used Film Dev.

Cheers

Edited April 3, 2022 by alacant

[Pitch Black Skies]

@alacant

M101 19 hr 10 mn calibrated.tiff

[symmetal]

I'll have a go with your file later but the main problem is you've overdone the noise reduction which makes the background look too artificial. The default setting in Startools is too strong. Some noise in the image is more realistic and fine noise makes it appear sharper. Also raise the black level in PS or Gimp etc. so it;s not so dark which will help reduce the background noise blockiness anyway and give a more pleasing image.

Alan

[vlaiv]

35 minutes ago, Pitch Black Skies said:

@alacant

M101 19 hr 10 mn calibrated.tiff 40.44 MB · 2 downloads

That is already stretched version like one attached above as image, so not really usable for anyone wanting to see quality of the data itself.

[Pitch Black Skies]

1 hour ago, vlaiv said:

That is already stretched version like one attached above as image, so not really usable for anyone wanting to see quality of the data itself.

Thanks, will attach un-stretched file soon.

[ollypenrice]

For me the main culprits are too dark a background sky and a mottled look to the background. This could be from noise reduction. It looks very shiny,  giving the 'vaseline on the lens' look. In Photoshop I like my background to be at 23 and the histogram to show no clipping. Your histo shows no clipping but your background is just over half what I go for, so it's very black. A lighter sky looks more natural.

I can see that you'd want a hard stretch to bring out the faint outer arms (which you have done) but that could be done using a stretch which flattened off earlier so as to give the main spiral less of a stretch.

In terms of colour balance your cyans are very high and are dominating the other colours. I can't say where this comes from but it can be remedied or avoided in many ways, dependng on what software you use?  It would be helpful to know that.

Olly

[vlaiv]

24 minutes ago, ollypenrice said:

I can't say where this comes from but it can be remedied or avoided in many ways, dependng on what software you use?

This happens a lot with startools when one uses their "color balance" feature. It produced unnatural cyan, green and yellow colors in the image.

@Pitch Black Skies

If you are aiming for natural looking galaxy image - it's worth consulting reference image.

core is much more orange / yellow glowing and outer arms are really not that blue. It is much more steel / white / light grey kind of blue.

Colors of stars are really colors of objects of a certain temperature. You can get pretty good idea of what sort of colors you should be getting in a galaxy if you simply take light of certain temperature - see this as an example and compare to above Hubble/ESA M101 image:

That is simply the range of colors that you'll see in a galaxy. This second image is taken as an example of what LED light of different color temperature produces.

Or the same scale from wiki:

going from 1000K to 12000K temperature.

[alacant]

9 minutes ago, vlaiv said:

when one uses their "color balance" feature

Which 'colour balance' feature'?

[Pitch Black Skies]

@vlaiv M101 19 hr 10 mn calibrated.zip

[Pitch Black Skies]

49 minutes ago, ollypenrice said:

dependng on what software you use? 

DSS for stacking, Startools for post processing.

[vlaiv]

9 minutes ago, alacant said:

Which 'colour balance' feature'?

https://www.startools.org/modules/color

[Pitch Black Skies]

3 hours ago, alacant said:

My guess is that you used Film Dev.

Yes, I start with AutoDev, Crop, Wipe, and then FilmDev. I typically stretch to between 96-97% in Digital Development.

[bottletopburly]

Maybe @jager945 can advise 

[alacant]

13 minutes ago, Pitch Black Skies said:

FilmDev.

This is designed for a look and feel of an old image from the film days. 

Try AutoDev instead of Film. 

 

13 minutes ago, vlaiv said:

https://www.startools.org/modules/color

Mmm. So in fact, any colour one chooses. 

Edited April 3, 2022 by alacant

[vlaiv]

Just now, alacant said:

So any colour you choose.

Interestingly enough - people seem to choose very similar but incorrect colors

even on help page by star tools we get this

Teal colors in the left image - no star has teal color.

 

[vlaiv]

I think it is down to processing.

Here is simple processing done in Gimp and ImageJ.

Color calibration is on a single star (B-V index of 0.16) and I did not pay much attention to color work flow, but data is good and sharp. Not sure what step in processing above resulted in "mushy" looking image.

 

[alacant]

16 minutes ago, vlaiv said:

the left image

Please read the caption. The StarTools image is the other one. Presumably you don't like that either.

Let's see if @jager945can help us.

 

 

[Pitch Black Skies]

45 minutes ago, vlaiv said:

I think it is down to processing.

Here is simple processing done in Gimp and ImageJ.

Color calibration is on a single star (B-V index of 0.16) and I did not pay much attention to color work flow, but data is good and sharp. Not sure what step in processing above resulted in "mushy" looking image.

 

Excellent.

It would be great to find out how I can produce something similar with just Startools.

Edited April 3, 2022 by Pitch Black Skies

[Pitch Black Skies]

1 hour ago, alacant said:

Try AutoDev instead of Film. 

So I am trying AutoDev after Wipe now but it is redoing the global stretch and looks far too aggressive. Is there a way of dialing it back a little? What do think I am doing wrong?

[Budgie1]

Not really helpful if you're using StarTools but, I ran your image through PixInsight to see that I could get with the data and here's the result.

 

[alacant]

16 minutes ago, Pitch Black Skies said:

What do think I am doing wrong

For the second AutoDev, you are selecting neither a region of interest nor setting the gamma, fine detail or shadows, after which the stars and background will be taken care of.

HTH

[bottletopburly]

23 minutes ago, Pitch Black Skies said:

So I am trying AutoDev after Wipe now but it is redoing the global stretch and looks far too aggressive. Is there a way of dialing it back a little? What do think I am doing wrong?

yes use a region of intrest over the galaxy ie draw a box over the galaxy to get  the desired look the smaller the box the darker the image will become essentially ,

[tomato]

Here is my effort, processed in APP, then the stretched image in Affinity Photo, trying to match the palette suggested by @vlaiv.

It's great data BTW.👍

 

[alacant]

 

StarTools 1.8.527mr2

Nice detail but still quite a bit of noise considering there's 19 hours. Are you dithering between frames and stacking with a clipping algorithm?

If you want the Ha regions, stick the red in NBAccent.

 

 

 

 

Edited April 4, 2022 by alacant
OP's question about AutoDev