How can I remove this extreme vignetting?

[feverdreamer1]

Hello,

Went to a trip to a Bortle 3 sky last december, just got time to start processing and all.

Stacking went fine, there were about 34 lights of 2 mins and about 30 bias (couldnt do darks because battery ran out before I could start doing them, no flats either for the same reason.)

The bias were taken the day after.

So, about an hour of exposure of M45 with a canon 550D, 55-250mm at 135mm and ISO 1250.

I thought i had some good data to work with, however, im starting to process it and it looks like it wasnt as good as I´d thought.

Whats really bugging me is this vignetting:

All I´ve done is adjust the black and gray pointers in Levels, but i get this ugly red haha.

 

Stacked file is:

https://drive.google.com/file/d/1sm-_MVfILDNd9aMexPY5KDnjoepCaOZ8/view?usp=sharing

 

 

Thanks in advance and clear skies!

Edited February 16, 2022 by feverdreamer1

[feverdreamer1]

Alright, have been touching sliders here and then and reached to this:

Looks much better, but theres still that vignetting, will continue messing with it hahaha

[scitmon]

I presume you know that flats remove vignetting, but are looking for an alternative because you ran out of time to take them?

[malc-c]

I would assume taking a load of Darks, Flats and Bias images ??

[feverdreamer1]

5 minutes ago, scitmon said:

I presume you know that flats remove vignetting, but are looking for an alternative because you ran out of time to take them?

Yes, exactly.

 

[feverdreamer1]

4 minutes ago, malc-c said:

I would assume taking a load of Darks, Flats and Bias images ??

Yes, but the only calibration frames I managed to get were Bias, as my camera died and ended up only taking lights

[teoria_del_big_bang]

I think without flats you will struggle to remove the vignetting totally. But there are tools to help remove it.
I am no expert but that is the single best way to do so.
I use Pixinsight and you can have a fair go at removing it but never as good as calibrated flats.

Is the image train still as it was when you took the images or did you dismantle it all ?
If it is I would take some flats now, they should do a fair job of removing the vignetting.

Also you can take darks anytime, but really should be same temperature so if the camera is not cooled then yes best to take same time. 

I will have a look later to see if I can do anything in PI to help, I might do better with the raw images though and there will be loads on SGL with more skill in processing than me but I will have a go.

EDIT:  Looks like others have now done far better than I could.

Steve
 

Edited February 16, 2022 by teoria_del_big_bang

[scitmon]

I would try taking the flats anyway, by getting the focus position as close as you can to what the lights were taken on.  If there are no dust bunnies then it might work better than not having any.

Edited February 16, 2022 by scitmon

[ONIKKINEN]

Take new flats with the same focus position and stack with those. Set the lens at the same focal length and get it to infinity focus either by using stars or something far away in daylight and then shoot the flats.

You can take a few different sets of flats with slightly different focus and focal length positions and check if one of them works. I would say its almost certain you can take flats that are much better than nothing and you can salvage the data. In the future try to shoot flats before the battery runs out, they are almost as important as the light frames themselves and you really do need them.

If you dont want to do that for some reason, or cant get them to work properly you can try the background extraction tool in Siril (free). It doesn't always work like i want to but it will definitely help with your vignetting here. I ran your pic through it:

The quality is not great because i just used your cropped screenshot JPEG, but it still worked a bit. Would expect it to work much better with the linear 32bit file straight off the stacker. If you try it out, i would recommend trying out Siril for other processing too, its much better than manual slider fiddling with GIMP/photoshop.

[Malpi12]

57 minutes ago, feverdreamer1 said:

Alright, have been touching sliders here and then and reached to this:Looks much better, but theres still that vignetting, will continue messing with it hahaha

some further messing in Gimp for you to try  :- construct an artificial flat,
Duplicate the image to a new layer then with with Filters > Blur > Gaussian Blur choose a size in both X and Y which is a large fraction of your image pixel  dimensions
Change its Layer Mode to Subtract then merge down.

Here is a quick first attempt to illustrate possibilities (it is a bit heavy handed !) using size 500 in both X and Y

I have cropped the margins as this method creates edge artifacts where the blur runs out of ststistics.
happy gimping ,,,Im no expert, give it a whirl,,, 

[steppenwolf]

Flats are what are really required here but this is what I did in PhotoShop:-

1. Levels

2. Histogram balance

3. Levels

4. AstroFlat plugin (also available for The GIMP)

5. Levels

6. Curves

 

[Laurieast]

GradientXterminator  works with that.

[ONIKKINEN]

2 hours ago, ONIKKINEN said:

Take new flats with the same focus position and stack with those. Set the lens at the same focal length and get it to infinity focus either by using stars or something far away in daylight and then shoot the flats.

You can take a few different sets of flats with slightly different focus and focal length positions and check if one of them works. I would say its almost certain you can take flats that are much better than nothing and you can salvage the data. In the future try to shoot flats before the battery runs out, they are almost as important as the light frames themselves and you really do need them.

If you dont want to do that for some reason, or cant get them to work properly you can try the background extraction tool in Siril (free). It doesn't always work like i want to but it will definitely help with your vignetting here. I ran your pic through it:

The quality is not great because i just used your cropped screenshot JPEG, but it still worked a bit. Would expect it to work much better with the linear 32bit file straight off the stacker. If you try it out, i would recommend trying out Siril for other processing too, its much better than manual slider fiddling with GIMP/photoshop.

Hmm, for some reason i did not notice that the original post had a link to the stacked file...

Well, anyway ran it through Siril and some photoshop fiddling afterwards:

Background extraction as a first step to the linear file worked very well and the image is perfectly salvageable. I stretched it a bit too far here, but this is a quick edit that shows you can work with the data without flats in this case, if necessary.

[Aramcheck]

Likewise - I did a quick & dirty process in Pixinsight. DBE did a fair job of removing the vignetting.

Cheers
Ivor

[feverdreamer1]

2 hours ago, Malpi12 said:

some further messing in Gimp for you to try  :- construct an artificial flat,
Duplicate the image to a new layer then with with Filters > Blur > Gaussian Blur choose a size in both X and Y which is a large fraction of your image pixel  dimensions
Change its Layer Mode to Subtract then merge down.

Here is a quick first attempt to illustrate possibilities (it is a bit heavy handed !) using size 500 in both X and Y

I have cropped the margins as this method creates edge artifacts where the blur runs out of ststistics.
happy gimping ,,,Im no expert, give it a whirl,,, 

Looks really cool, and will definitely use that method and test it out. Great job given the data. Thanks!!

 

1 hour ago, steppenwolf said:

Flats are what are really required here but this is what I did in PhotoShop:-

1. Levels

2. Histogram balance

3. Levels

4. AstroFlat plugin (also available for The GIMP)

5. Levels

6. Curves

 

Yes, after this, flats will be a MUST in every session, glad to have learnt the lesson, even in the hard way haha.

Great image, really like the sky color you got.

1 hour ago, Laurieast said:

GradientXterminator  works with that.

Will look into it!

 

34 minutes ago, ONIKKINEN said:

Hmm, for some reason i did not notice that the original post had a link to the stacked file...

Well, anyway ran it through Siril and some photoshop fiddling afterwards:

Background extraction as a first step to the linear file worked very well and the image is perfectly salvageable. I stretched it a bit too far here, but this is a quick edit that shows you can work with the data without flats in this case, if necessary.

Ive never used Siril, but the image proves I really should, will take everything you said into account and will try to learn Siril and edit it again. Many thanks!!!

 

19 minutes ago, Aramcheck said:

Likewise - I did a quick & dirty process in Pixinsight. DBE did a fair job of removing the vignetting.

Cheers
Ivor

Yep, image is prefectly salvageable, thanks a million Ivor.

[feverdreamer1]

Ill add my final edit too, played with curves and levels, a bit of saturation and crops here and there:

Loads of noise I know, but Im happy with my results.

Again, thanks everyone and Clear Skies!!!

 

[Malpi12]

43 minutes ago, feverdreamer1 said:

that method and test it out. 

It is good for star-fields and small nebulosity  but wipes out wide nebulosity which it thinks is background !

 

41 minutes ago, feverdreamer1 said:

Ill add my final edit too, played with curves and levels, a bit of saturation and crops here and there:

I like it, good rescue

Edited February 16, 2022 by Malpi12

[michael8554]

22 hours ago, feverdreamer1 said:

an hour of exposure of M45 with a canon 550D, 55-250mm at 135mm and  ISO 1250.

I don't remember the reason, but choosing ISOs that aren't whole-stop increments is not recommended for long exposures.

So use ISO 800 or ISO 1600, I would say 800.

Michael

[feverdreamer1]

3 hours ago, michael8554 said:

I don't remember the reason, but choosing ISOs that aren't whole-stop increments is not recommended for long exposures.

So use ISO 800 or ISO 1600, I would say 800.

Michael

Oh, didn´t know, will remember it for next time, cheers!

 

[Ricker]

I would suggest that you could try startools.  Wipe can flatten uncalibrated frames. Free to try.