Quote:
Originally Posted by topheart
...It is a bit of a shame about the elongation .....but I can't see how anything can be done about it with processing with everything packed in so close together.....what do you think??
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I don't know how you would do it in PI, but in PS, it's easy.
Disclaimer: nothing will fix elongation
perfectly but it can be
mitigated if the elongation is of the order of about a pixel or two (at the outside) like yours. Much more than that and you'll still end up with misshapen stars or other artefacts.
In Photoshop:
- Flatten
- Enlarge the image by 300% (to allow sub pixel manipulations)
- Duplicate the flat layer
- Change the blending mode of the duplicate to Darken
- Select the whole image
- Zoom in to an edge so you can see the pixels and an elongated star
- Using "Free Transform", grab & shift an edge (on one axis) to reduce the elongation on that axis
- If the elongation is diagonal (elongation along 2 axes) repeat for the second edge/axis
- Always overdo it a bit and then use the opacity slider to blend the darken layer to achieve the best result (blink between the before and after)
- If only a corner is elongated, you may need to use a mask on the darken layer to expose only the elongated area (with a very large fuzzy brush to get seamless transitions)
- Reduce the image back down to 100% scale
NOTES:
1) Transforming from an edge will result in stars closest the the edge being altered the most while leaving those on the opposite edge unaffected. The effect will transition smoothly between the near and far edges/corners. This is good when elongation is more pronounced on one edge or corner.
2) If the elongation is uniform across the image then
move the darken layer in the direction of the elongation rather than free transforming
3) it's
not necessary to operate
only on the stars since the whole image is affected by the elongation
4) if you have a star rounding application, script or plugin, that can help but only after the transformation. I don't use a star rounding tool
5) if you have a sharpen tool with motion blur that can also be beneficial (if the result is blended as darken) but it will affect the whole image equally and you will have a use a mask to isolate the area of the image affected by elongation
6) purists (and those with perfectly accurate equipment and guiding and zero flexure) hate this kind of stuff but as long as you only try to fix small elongations (of the order of less that two pixels) it can render the elongations practically invisible without significant side effects
Sorry, lots of words to describe something quite easy!
great vista Tim, the gold looks spectacular!
A little elongation but it doesn't detract from the overall effect. Beautiful star colours and a lovely golden field. Nice work!
, (hardly ever an issue since using the small chip and OAG) but I found it not a great solution in a heavily stared region like Tims, it was always still noticeable....but certainly worth a shot and like you say, best when only a tiny amount of elongation is being delt with aaaand I may well not have applied it as masterfully as you too 
