Help needed identifying this aberration

[Lee_P]

Hi SGL, I'm posting this on behalf of a friend. He's just bought a used RedCat 51 and has taken some test shots using a Canon ESO 700D on a Star Adventurer. The stars look like teardrops, and he says it's the same regardless of exposure length. He's confident that the images he's taken are in focus.

Here's an example image, and the result after I ran it through PixInsight's AberrationInspector. My initial thought is coma and / or sensor tilt, but I'd appreciate the opinion of anyone more clued up on this particular topic!

 

[vlaiv]

I'd say it is collimation of the scope.

Sensor tilt would present as different in different corners - while center would be good (or could be focused to good sharp stars).

Maybe imaging bright defocused star (in/out focus) in center of the field would be more telling?

 

[ONIKKINEN]

All of the tails point roughly to the same direction, which could be thermal issues if its not collimation related. Ask your friend if the scope was well cooled down to ambient before shooting?

Needs a minimum of 1hr outdoors to be equalized (or have a chance to be).

[tomato]

Would sag in the imaging train create this effect? Does your friend have a fully screwed together imaging train, or is there any play in the focuser?

Do the tear drops change orientation on the other side of the pier/tripod?

Edited November 28, 2022 by tomato

[Lee_P]

Thanks everyone, I'll relay this info.