Refractor star artefact

[sj777]

Hi,
Does anyone know what would be causing each star to have a little dot beside it at the 3 to 4 o'clock position? The image is a snip of the center of the field of a larger frame.



(https://astrob.in/15eajn/0/) https://astrob.in/15eajn/0/ (https://astrob.in/15eajn/0/)

The image train is:
Sharpstar 72ED Refractor

ZWO OAG
Threaded spacers 11mm and 21mm
ZWO ASI183MC-Pro


I normally have an orion FF in the train but removed it before taking this image to try to eliminate that as a contributor to this problem.


I took images at 60s and 120s with binning from 1x1 through to 4x4. The artifact is there in all of them but it is harder to see in the higher binned shots.

[gregbradley]

Looks like bad guiding errors. That will do that.

Greg.

[sj777]

Thanks Greg, attached is a screenshot of my guiding stats at the time. I thought it was doing well - can you comment if you see anything I should look into?

[gregbradley]

There are several big spikes there. Possibly they caused it.

Greg.

[sj777]

Thanks Greg, I'm going to spend some time tuning the guiding. Thanks

[gregbradley]

If your mount does periodic error correction (PEC) that would help smooth it out.

Greg.