Congratulations!
Saw photos and read an article yesterday about how tight collimation screws appear in star photos. To apply my new "knowledge", I investigated your photo.
And guess what I found: Tight collimation screws.
Or not?
The first screenshot is the bottom right corner of your image.
The second is taken from the mentioned article.
http://interferometrie.blogspot.com/...l?view=sidebar
I'm that far from being an expert as we are from traveling to Andromeda galaxy.
So what do the others say? Is that negligible? That it doesn't show in the center stars might just be because they're over-exposed in this test shot.