Sorry to come again with my question. I am using the Infinity Color with my C14 and a shapely lens to reduce the focus to about f/5, that is about 2 meters focal length .
Stacking does not work unless I turn off the "Calc Image Movement"- possibly I have a tracking problem? Visually the very solid mount keeps the stars for many hours exactly in the center - but there are some little movements of about 1 arc minute which never disturbed my visual observations. Furthermore the seeing is currently very bad, so that the star is "hopping" considerably in the eyepiece.
I wonder whether the "Calc Image Movement" can manage such movements in a C 14 with a relatively long focus. (Stacking images of my Celestron Planet Camera does not cause any problems.) What are the limits of "Calc Image Movement"? What can I do?