Astrofriend's homepage

www.astrofriend.eu
Share: Twitter Reddit Facebook Gmail Gmail Email
Search Astrofriend's homepage:

Valid CSS!

All pages shall now have been validated

Info Cookies (Kakor) / GDPR

Navigation

Advertisement /
Annons:

Twitter @AstrofriendLars

Follow Astrofriend

Astronomy Project News

Advertisement / Annons:

Tutorial:
Gimp for astrophotography


Content:

Note:
I take no responsibility or liability for what are written here, you use the information at your own risk!


Separation of stars and DSO, part 1.4:

Test of background mask:

Separation of stars and Deep Sky Objects, Gimp

Set 'DSO mask' and 'Stars + DSO copy' visible. The mask has made 'holes' were the stars are. They look a bit big, but first do a test before go back and do changes.

Later I shall fill the 'holes' with the color from the surrounding edge.


Add mask to 'Star mask':

Separation of stars and Deep Sky Objects, Gimp

Change the visibility to the 'Star mask' layers group. Right click on 'Star mask', choose selection AND invert the selected area.


Test of 'Star mask':

Separation of stars and Deep Sky Objects, Gimp

The mask work correct, but look a bit big as mentioned earlier.


Overview of the mask selection area:

Separation of stars and Deep Sky Objects, Gimp

Zoom out, the area around the Open Cluster M45 is very cluttered of stars. I have to do trail and error method to find the correct size of the mask 'holes'. It vary a bit for every image dependent of camera, telescope and object.

Note:
What I do here is very rough, a lot of tweaks to get it perfect. Just the basic so you can start with Gimp.


Star Mask copy:

Separation of stars and Deep Sky Objects, Gimp

I make a copy of the 'Star mask' too have as a fill area for the DSO layer.

Erode:

Separation of stars and Deep Sky Objects, Gimp

These areas are to use to fill the holes in the DSO mask later. I want them as a flat area. With the Erode tool I expand the blackest area in each star hole. Menu: Filters>Generic>Erode. Note: I have the layer 'Stars + DSO copy' active !

Erode:

Separation of stars and Deep Sky Objects, Gimp

This is the result of one erode, the stars is still visible, run Erode once more. You can use 'Ctrl' + 'F' to repeat the command. Totally I did two Erode.

DSO with filled holes:

Separation of stars and Deep Sky Objects, Gimp

The result, with both Star and DSO mask activated. The bright stars are gone.

Go Back to content

Go Back
Next: Separation of stars and DSO, part 1.5

Advertisement / Annons: