Not being happy with the crude focusser that comes with the Tal 200K, have finally come up with a solution. Removed the Tal focusser completely and replaced it with some Hutech components.
Have not tested it yet but the focus action is very smooth and lockable and non rotating. There is also room for a filter box for 48&52mm filters. The clear aperture is 47mm. Will test it as soon as possible.
The really nice thing as well, it is removeable (57mm screw) and can be used on any other telescope eg 80ED.And best of all also compatible with Hutech field flattener/focal reducer.
No it is not coma, it is a combination of field curvature and slight main mirror misalignment. I am going to realign the main mirror and get rid of the field curvature with a Hutech focal reducer/field flattener.
The Canon 5DH is a fullframe (25X36mm) camera so any field curvature becomes more noticeable. We have all been lulled into a false sense of optic quality by the smaller sensor sizes which only see the 'good' inner 'flat' part of the image.
