I can’t see the attachment for some reason (was it below the maximum 640×48 size?) but my field has significant off axis coma, something I plan discussing with Francois at the workshop. I believe it is a feature of the guider optics and it is ok close to the axis where the slit is but I would be interested to explore if it could be improved as sometimes I would like to be able to use guide stars well off axis. I have attached an example guider frame from my setup
The shadowing might be because the mirror slit in the ALPY module is not quite aligned at the optimum angle relative to the guider. You can rotate the ALPY module to optimise the illumination and then rotate the guide camera to align the slit in the field. My slit is slightly offset. I am not sure where this arises, possibly in the camera coupling. These will be good subjects for the workshop however when we have Francois to demonstrate how to set the spectrograph up optimally.