Gimp for astrophotos, tutorial

[Astrofriend (Lars)]

Hi,
Have you noticed how advanced Gimp has been with the new version 2.10 ?

Now it work perfekt to open Fits 32 bit floating point images and process them. I have tried this many times earlier but it never worked very good. Now it's like a dream to work with.

I'm in the learning process how to use Gimp's capabilities. I have now got the opening process of three grey rgb images to work. It's of course not very complicated, but for me who never used Photoshop or something simular it was and I have hard to find a tutorial for the new version.

I have now made a tutorial for this first step how to start with Gimp and open 32 bits separated color images:
http://www.astrofriend.eu/astronomy/...roduction.html

If you already working with Gimp, have you found something of special interest ?

Lars

[rustigsmed (Russell)]

thanks for sharing Lars.

really no need for photoshop with how powerful GIMP is these days. it is just that all the old tutorials are for photoshop, so its definitely good to have some now for GIMP.

cheers

[Astrofriend (Lars)]

Hi Russel,
Yes, very interesting. I started to practice on separation of the stars and DSO. I got it to work but the mask around the stars got to big. I have to take a pause now, others things to do as well.

http://www.astrofriend.eu/astronomy/...roduction.html

/Lars

[Astrofriend (Lars)]

I have now optimized the selection area around the stars, I also changed my workflow a bit to get it easier to do.

http://www.astrofriend.eu/astronomy/...roduction.html

I'm not finished yet, but will come back soon.

/Lars

[skysurfer]

The problem with GIMP is, that is does not support adjustment layers, what Photoshop and Affinity Photo do.
Adjustment layers are a non-destructive way to adjust the underlying layer and can be corrected indefinitely.

That is what I miss in GIMP.

[Astrofriend (Lars)]

Hi,
That like something good to have, but Gimp develop a lot and maybe that functionality will be there in the future.

What I do is to make a copy of the original layer with only level and crop adjustment. Never touch it after that.

I have added and corrected some parts:
http://www.astrofriend.eu/astronomy/...roduction.html

/Lars

[Astrofriend (Lars)]

A question on a forum about calibration for vignetting with Gimp got me curious. Is it possible ?

After some test I found it to be very easy to do, see my example:
http://www.astrofriend.eu/astronomy/...roduction.html

I will still do flat calibration in AstroImageJ, but for others this can be useful.

/Lars

[kamayok3]

Hi Lars,

Is it possible for you to do a series of tutorials on how to use these plugins in Gimp?

http://www.hennigbuam.de/georg/gimp.html

Thanks

[Astrofriend (Lars)]

Hi,
Maybe the person who developed the plugins will create a manual later. It will take weeks for me to do. I try to use only the functions that are already builtin Gimp, at least for the moment when I'm in the learning process.

The page with plugins you linked to looks to have the latest 32-bit functionality built in. Interessting for the future, I think a lot of plugins will be developed now when Gimp handle 32-bit format..

/Lars

[Astrofriend (Lars)]

Hi,
I have some old photos of comets taken on film and to the first digital cameras I didn't have correct flat frames. I have used AstroImagesJ to make synthetic flat frames. But didn't work very well when the shape of the vignetting was too complicated. Then I took a new look at Gimp and what it can do. Found it to be very advanced and relative easy to correct the vignetting.

I added a new page on my Gimp tutorial how to do this:
http://www.astrofriend.eu/astronomy/...ignetting.html

Merry Christmas to you all !

/Lars

[Astrofriend (Lars)]

One rainy day I sat here with Gimp, I got dark pits behind my comets when doing darksubtraction. Testing a new method when I divide the Gaussian Blur filter to a two step process. Much better now.

Here how I did it:
http://www.astrofriend.eu/astronomy/...btraction.html

/Lars