Anyone have advice on why I have weird stars in this image?

[Cumbrianwolf]

My feelings are that the scope cooled down a bit more than I expected after collimation and that the collimation went out? Or would I be barking up the wrong tree?

Canon EOS 7D 254 mm F/4 1016 mm coma corrector and 30 second subs at ISO 400. Image below is not stacked and no editing.

 

Edited March 2, 2022 by Cumbrianwolf

[Cumbrianwolf]

I found the issue, during my cleaning of the primary mirror I failed to notice that the primary mirror clamps or at least two were quite loose, so the mirror could move ever so slightly and during collimation it was probably seated fine but vertically or horizontal it would have slipped and at F/ 3.5 with the corrector there is not much room for error! Now the primary has been recentred, and the secondary realigned by both laser and Cheshire collimating eyepiece, I have also thread locked the screws on the rubber mounts, so no more movement of the primary for a while at least.

[Carastro]

Glad you found the cause of your problem.

 

Carole 

[Cumbrianwolf]

38 minutes ago, Carastro said:

Glad you found the cause of your problem.

 

Carole 

Thank you, I lost a lot of hours worth of data due to the issue, but in hindsight I should have kept an eye on what images coming back from the rig so that I could have intervened sooner. You live and learn.

[GazAstro]

I had that on my SCT when the secondary screws were too tight.

[Cumbrianwolf]

16 minutes ago, GazAstro said:

I had that on my SCT when the secondary screws were too tight.

It is easy to miss these things as you just do not think it will ever be an issue but these fine threaded screws do and will come loose, guess the constant expansion and contraction loosens them over time. Semi-permanent thread lock will now be used on all the fixture and fittings that should not move from now on. Not had the pleasure of a SCT, currently. 

Edited March 4, 2022 by Cumbrianwolf

[Cumbrianwolf]

Well the problem was not the actual problem, I have some issues going on with this scope and a full strip and realignment is in order tomorrow as tonight was a wasted effort.

[TerryMcK]

Hopefully you will get to the bottom of it tomorrow John.

[Cumbrianwolf]

Stripped it down, cleaned all mirrors and reassembled the OTA and of course fully collimated it with both the laser and the Cheshire eyepiece so that should rule that option out. Also checked the coma corrector for any flaws that could be present and cleaned that optical glass as well. The full kit and caboodle is now set up and ready in advance for tonight.

Looking back on my other images that I first took, I can also see the triplet star deformations, so something is a miss.

[Cumbrianwolf]

Good news I have now sorted the issues and my images which I am working on have some superb data, there is a slight cast on the stars but only when you zoom in, and I think that was more of a tracking error. M42 is in the works with 90 minutes of exposure, let us see how my editing goes on this one.

[TerryMcK]

AP is all about problem solving and glad you have got it sorted now John 🙂