Focusing is not as critical for autoguiding as for imaging, as even a moderately fuzzy image can be used to generate an accurate centroid. Very bad focus can however result in a loss of sensitivity, as the starlight is smeared over more pixels.
For most dual-chip SBIG cameras and STAR2000 equipped Starlight Xpress cameras, the tracking CCD is automatically in focus once the main camera is focused.
When using a separate guide camera, manual focusing can be performed normally using the Expose Tab, by selecting the appropriate camera using the Camera 1 / Camera 2 selector. Autofocus is also available, if the autoguider camera is equipped with a digital focuser.