[Stephane]

Hi all,

Recently I finally managed to fix my diffraction spikes. Great news. However, my image of the Sombrero galaxy suffers from bad eccentricity and poor focus in the corners. Could I please pick your brains to analyse my image and give me some possible indication of where I might start?

My images often suffer from bad eccentricity with about a third of my frames above 0.7, but last imaging session was worse than ever where 2/3 were above 0.7. Coma looks particularly bad in 2 corners. Previous images have almost been coma free.

Thanks so much for your help.

Regards,
Stéphane

Notes:
- I am using a Newtonian reflector with a coma corrector at about 56 or 57mm from the sensor.
- Poor polar alignment could be a problem. I might be doing something wrong, but for me, NINA's 3-pt polar alignment is inconsistent.
- Flexure could be another problem. My guidescope is not tight enough and my OTA image may not have been at the centre of the guiding image.