Wednesday night I put the laser collimator into the eyepiece and adjusted the secondary until the return beam came straight back onto the target. I know this is not going to produce anything like perfect collimation but I figured it may at least get it into a ballpark of correct. Originally the return beam was only just inside the target.
Tonight (Thursday) was relatively clear and the moon getting quite bright now so I figured this would be a perfect time to try again as I could easily see what I was doing. So I set it up in the backyard and pointed it to Mimosa as it was away from the Moon and was not hidden. The image was certainly MUCH better than earlier, it looked like a very bright comet but at least I could see something.
I adjusted a couple of screws and was able to reduce the coma significantly but eventually it became frustrating trying to remember what it looked like before I had made an adjustment, so it was time to call in my trainee collimator (wife). She looked in the eyepiece as I adjusted the screws letting me know if the image got smaller or the tail started to disapear. After a frustrating 30 minutes we had to give up. As I adjusted a screw, the coma no longer appeared to get any better. The image moved across the field and the coma appeared to change direction, but it didn't appear to get much better. I was using a pentax XW-7 so I don't think the coma is in the eyepiece...certainly not to this degree. Adjusting the focus made only a small improvement, but the coma was always there.
So...am I doing something wrong? I there a trick to getting the alignment better. I was expecting that as I turned one screw the coma would get shorter and then get bigger again. Adjusting another screw would bring it in further until eventually I would only need to iterate gradually between two screws....
?