Egg shape stars

[Tim Jennings]

Good evening, I'm  having problems with imaging, here is a photo of andromider. If you look at the  corners you can see, that the stars are funny  shape I'm  not guidering so could this be the problem. I do have a guider camera,  which is the ZWO 120 and the svbony guidescope. But not shore how to set it up, the mount is the Celestron  AVX mount and I'm  using a dslr camera, which is the Canon 60d mod

 

 Tim

 

 

[carastro]

The elongated stars are more in the four corners.  This suggests spacing to me more than guiding as the middle looks OK as far as I can see, (need a more zoomed in picture to judge properly.

Spacing is the distance between your Flattener/reducer and your imaging chip.  If you don;t have a flattener, then that too could be causing it.  

Carole 

[michael8554]

Hi Tim

The image is pretty low-res, only 500MB, you can go up to 1GB with images.

But it looks to me that the centre stars are elongated.

And the amount of Coma in the corners varies, due to Tilt.

Examine a short exposure of a starfield, to minimise guiding and PA errors, stretch that single image if necessary.

Michael

[alacant]

14 hours ago, Tim Jennings said:

. If you look at the  corners you can see, that the stars are funny 

Hi

If you're using a telescope, fit a field flattener (FF) and ensure that the camera and FF assembly are held fair and square to the focuser. 
We don't know which telescope or lens you are using (or maybe it's in the signature which I can't see)  so it's difficult to offer specific help. But hey, well done. A worthwhile image no matter what.

Cheers

Edited December 1, 2023 by alacant
your you're

[Tim Jennings]

Hi thanks for the info. The telescope is the  Sky-watcher EVOLUX 62ED which has a ff on it. But I do have a filter draw on.

Tim

[alacant]

Which FF is it and how far is it from the sensor of the camera?

The image suggests it's too close.

[Tim Jennings]

Hi, it's a EVOLUX 62ED .9 Reducer/Flattener. Can you   remind me  how to work out the 55mm back  focus  please.

Tim

 

[alacant]

From the end of the FF closest to the camera to the plane of the sensor. The latter is marked on top of the camera: ø

What adapter do you have to attach the FF to the camera bayonet? How thick is it?

Edited December 1, 2023 by alacant

[michael8554]

Hi Tim

The EVOLUX 62ED .9 Reducer/Flattener has 55mm Backfocus.

So will have the correct spacing on a Canon DSLR with the usual 11mm T2 Adapter.

But that distance can be increased if the star shape suggests the FF is too close.

Which a filter will have already done.

Though if you get the Tilt corrected the coma may be gone too.

Looks like a the connections are screw-threaded, so I hope the tilt isn't due to the DSLR mod :-<

Michael