SCT autofocus HFD Parameters determination

I use a C11(focal length 1630…has a reducer) with an Optec TCFs focuser attached. The TCFs only have about 7000 steps to work with. I’m having problems getting the first light curve working unless I play with the HFD Parameters. I am not confident that I’m doing it correctly to make sure I’m getting the best focus. The Curve limit always has to be adjusted down from the default. My steps are as follows to run the curve:

  1. find appropriate star
  2. set the tcfs at 3500(midpoint) and manually focus the sct for the best hfd I can get.
  3. run the wizard.

The VCurve limit needs to always be adjusted down from the defaults (I do this by trial and error until the function doesn’t error out). But what about the other parameters of Near Focus and Start Focus? Are there rules on how to establish them? I assume the Near focus should be set based on the point where the Vcurve goes non-linear as you near focus. How do you determine the start focus point? Is there a relationship with the Vcurve limit? What should I look for in the logs?

The sct is affected by temperature so much that I need to re-run the focuser set up as the seasons’ change. I’d like to get good at adjusting it as needed. Are there any other parameters to look at?

Any responses are appreciated.

You will found so many topic about in the forum.
You must choose the 3 HFD kind of points out of not linear part of vcurve , the points must be distribuited at equal distance in the linear part, VCurve limit at top possible of large HFD allowed by your travel. Near Focus at begin of linear part of vcurve. Best pratice is to change only the vcurve limit. At least leave 4/5 point of HFD between the 3 points.

Remember to use the green button to select the focus star and do not do manually:

Opening a support request if you want to do it togheter supervisioned from remote.

All the best