Very bad stars...

[Wyvernp]

Good morning, I was hoping I could get some guidance on improving my star shapes. 

Here's 2 hours of data from M97 last night stacked in siril.

The nebula itself I think looks ok but the stars are hideous

Here 2 of the exposures pre and post refocus so I think I have ruled that out, could it be collimation?

pre refocus

post refocus

Thanks in advance.

Wyvern

[almcl]

It would help to know what equipment you're using?

If a reflector, do you have a coma corrector?  If so, which one and at  what spacing?  

What camera, and how is it attached?

How are you focussing, Bahtinov, manual or auto focus?

[Wyvernp]

Yes..quite haha

The Scope is a nexstar 8se with the f6.3 reducer which I know is a very hard scope to learn on but making the most of the equipment I have until I can get an 80mm to learn on.

Again, until my cmos arrives I'm using my olympus omd e-m10 m4/3

Focus is using a bahtinov mask.

[vlaiv]

I'm seeing multiple aberrations in star shapes.

This is typical coma:

Parabolic newtonian telescopes and SCTs have coma aberration. As far as I know - x0.63 reducer should be both reducer and corrector and should remove coma.

This other corner shows coma + astigmatism:

With setup as yours this usually means that you have a tilt in your system. If one corner is affected and others are not or there is different aberration present - it means that sensor is tilted with respect to optical axis and corners are at different distance to corrector because of that.

Check corrector spacing and connection to camera. Reducers/correctors have a working distance - make sure you get it right to remove coma. For astigmatism - make sure your camera connection is straight and firm (does not sag under camera weight).

 

[Wyvernp]

Thank you, I can definitely work with that. will strip down the camera tube assembly ans make sure everything is nice and tight.

[Wyvernp]

Yep! I found a wobble in the imaging train, Now all tight.  Hopefully I'll have at least a little clear sky tonight to test. Thanks again.

[vlaiv]

2 minutes ago, Wyvernp said:

Yep! I found a wobble in the imaging train, Now all tight.  Hopefully I'll have at least a little clear sky tonight to test. Thanks again.

Do check spacing as well - just to make sure.