Rally, sorry was really cranky last night after spending several weeks just doing all the reading and trying to get this working well but things were defeating me a little. I am really happy all the system works under Vista but getting better results is the issue for me.
I tried changing the 6 main terms to see what effect it had. So I am with you there, this produced the best pointing effect. I agree not necessarily the best result either.
Yes looking through the fits file again last night and having read Brad Moores recommendations of sigma being less than half of the value. No matter what I do here the issue is not the model itself at present it is the way the data is gathered. Until that gets good results then the model manipulation is really a moot point.
The camera is attached using the standard Tak tension screws (yes it should have a screw in adapter but I have the flattener in place for both the tak and the RC and there is no screw thread on the flattener just an inserted end to the focusor) and could well as you point out be causing the problem. I will check this out tonight and use your suggestion of using some pressure to determine if there is some flex. I did this for eliminating flexure before when I was getting bad differential flexure so I know what you are suggesting here. It had not occurred to me that this might be an issue. Good tip this one. I will check it out.
PA results seem fairly easy to manipulate though. Removing a couple of stars can affect the model and suggest good PA. I am going to check with my own eyes tonight and see what drift I am getting. I take your point though about the ME. It ought to be a lot better than that for such PA.
How good does it need to be. Hey I would be happy with 50-70 RMS pointing. 40 would be great as far as I am concerned but 50 is realistic I think. That would put me near the center of the sensor each time. as 125 was putting me on the edge when I did this all by manual. I then simply nudged to get it center. I just want better point than I did have. Certainly have no illusions that this mount could be anything near the value you suggested.
Yes the guiding and PEC do sort this but it is the pointing I am after.
Thanks again for your help.