Thoughts on this image

[HighHo]

So nothing special in this image was just my DSLR pointed to the sky, and then images stacked. Most of the image seems fine, but certian points look like they might be repeated just wanted some thoughts it was stacked in DSS.

[HighHo]

Guess my link wasnt allowed, couldnt see how to edit my post so attached a lower res image.

[dph1nm]

Probably lens distortion. DSS does not correct for distortion - just rotation and translation.  As the lens distortion stays fixed wrt the lens orientation but the sky rotates, it becomes impossible to stack perfectly, usually around the edges of the image.

NigelM

[HighHo]

Perfect, many thanks for taking the time to explain. I suspect DSS may not have also had enough refrence points as this was has a higher optical zoom giving only around 50-60 detected stars, but my other quick test was something around 200+ stars which didnt seem to have this issue (only around the very outside of edges as you mention).

[dph1nm]

DSS only really needs 8 stars (in common between the subs of course) to do its alignment.  Anything else is probably overkill.  However, I guess it is possible to get an incorrect match by chance on very dense fields.

NigelM