Tutorial on star elongation removal
Using the action set available HERE
We'll start with a typical elongation. This one seems to have a tad of elongation to the top and bottoms of the stars.....download it if you want to use it in the tutorial.
As you can see we have some elongation do to inadequate polar alignment…this was very typical of my pictures before I learned how to do a proper drift alignment.
These actions simply use the offset filter to move a pixel in one direction and then use the fade filter to make it a very, very slight change.
In this particular example we'll use the nibble top and nibble bottom actions. I like to zoom way in to examine the stars as I invoke the actions. These actions will leave a new layer each time it is invoked. So, just nibble away until you get it as round as you can. If you use the actions five times, then you'll have an extra 5 layers. Simply turn off all of the layers but the original and the top layer….now click the little eyeball to see the difference….if you went to far then simply go down the stack of layers until you find the one that looks best….throw/drag the rest to the little trash icon at the bottom of the layers palette. (you can cntrl click all of the layers to discard and drag them all at once.)
Here is a little gif showing the before and after effects….again, remember we have blown up this image a bit.
You can nibble away as much as you want, but, depending on the star elongation it is usually good to take a little from each side of the elongation.
If you have galaxies or nebula, it must be understood that this is also going to change the nebula and galaxy arms also. This is sometimes not noticeable at all, in fact sometimes tends to sharpen the image abit. But, generally this is not desirable…..but can be fixed very easily.
Once you have thrown away the extraneous layers…you should now have your original layer below the repaired star layer.
Simply add a mask to the repaired/Nibbled star layer….then go to the bottom of the palette and click on the mask icon. It is the little rectangular icon with the circle in it.
Now choose a soft paint brush…opacity to about 40% and flow 40% (maybe less or more)…and now simply paint black paint onto the picture…..this is actually painting onto the mask…and the black paint will allow the bottom, unmodified nebula area, to show through.
Just paint the black wherever you want the bottom layer to show through. If you go to far, then just switch to white and paint over the area again and it will hide the lower area.
The removal of the elongation sometimes also makes the very small stars disappear….you can use the above method for bringing these smaller stars back into the picture.