Struggling with a star in the elephants trunk

[upahill]

Hi all,

Would be interested to know whats causing this artifact, its only on the one star - i assume due to its brightness. But Im confused why the halo would be off centre?

Is there a method to removing this? Any tips appreciated.

This is a stack of about 5 hours. 5 Min subs.

[michael.h.f.wilkinson]

The point-spread function of optics can become asymmetrical off axis quite readily. This even happens in big professional telescopes

[glowingturnip]

the Garnet Star, isn't it ?

[upahill]

2 minutes ago, glowingturnip said:

the Garnet Star, isn't it ?

Just looked it up, it sure is, Erakis aka Mu Cephei aka Garnet Star

100,000 times brighter than our sun is pretty impressive! Would explain the difficulties. ?

[don4l]

I recently noticed that my halos all shifted after a meridian flip. 

My unmounted filters were a bit loose and they had moved!

 

My halos are off centre because the reflecting surface  is not 100% perpendicular to the optical path.