These directions are posted at the registry also under the galaxy filter page from sambrookjm.
I asked him to add a few features to the filter to create these effects.

Let's begin the tutorial -
Create a new document with 1920×1200 pixels (72 dpi) and fill canvas with color #000000
Make a new layer above the black one and fill it with pure white color (#ffffff).
We have now two layers: the black one and the white above it. For the layer with white color we change the Layer Blending Mode to Dissolve, layer opacity 1% (no more than this amount) and get something resembling space.

The next step is the critical one - this creates each dif new galaxy nebula cloud arm
Create a new transparent layer name it nebula - paint the strokes.


Then a whirl and pinch


rotate to your liking and apply motion blur


Then whirl and pinch again


Set the perspective


Time for some color-
Create three new layers - name them nebula-colors 1,2, and 3, and change the layer Blending Mode to Color.
Grab the paint brush tool - Set the opacity of the brush to 10.0, and the scale to your liking - use the circle fuzzy 17 brush - select the color - 5a78cc
Select your new nebula-colors layer1 and paint over the galaxy like this
first layer -


change color to #ff0000 to add red color
second layer - nebula 2


change color to #fff000 to add yellow color
third layer - nebula 3


of course the colors could be optional.
Now just add the center core or bright spot. a white circle in a yellow one two layers
Blur and set opacity to each at your liking -



Here is one i just did with those exact directions except i added a dup layer of nebula clouds and set that duplicate layer to dissolve for a more intense ring feel.

You can of course then set that layers opacity to your liking.

Thanks for checking out the tutorial.

I've used whirl/pinch to create galaxies too (actually my preferred method). I actually use a flower brush that I created along with Supernova to make the center bulge or quasar. Used a starfield script-fu to create the stars. Why green arms? Why not. lol

You know, I was thinking, the Starscape script works nicely with these sort of images. And they, too, are adjustable.

http://registry.gimp.org/node/297

Looks promising Mahvin. Forgot to link the Script-fu that I used for the Starfield. Added color noise layer set to color to change the monochromatic starfield to a little more colorful one.

http://registry.gimp.org/node/24798

Stanfield filter added -

Stars in the sky was two dark for me, that script would be better served with gradient color options, IMHO. And star scape needs sparkling stars, square pixel dots just don't always cut it.