I tried finding a thread on this but have not come across any. Never thought much about imager / guide camera parameters.
I have been using a ccd camera with 9x9 micron pixels on a 1000mm scope (approx 1.85 microns/pixel) using a guide camera with 13 x 15 micron pixels on a 400mm piggyback scope (7 arcsec/pixel). With this setup I have been getting nice round stars and good tracking for years. I recently upgraded to an asi1600mm and though the guider movement appeared nominal, the stars in the subs were not round any more. I looked at balance changes and other issues to pin down the problem with no success.
Last night I crunched some numbers.
I think larger pixels of the guide camera were hiding errors that now show up with the 3.75 micron pixels of the new imaging camera. I ordered an asi120mm mini (approx. 2 arcsec/pixel) that better matches the pixel size of the 1600 / 1000mm scope (0.77 arcsec/pixel) combination.
Hoping this will settle down my guiding.
Wonder whether my logic is correct and if others have had similar experiences when switching imagers.
Incidentally, I have an OAG coming as well.