Autoguider Focus at Prime

It is most unlikely that the autoguider will be detectably out of focus if the system has been set up correctly. However, if the images look very extended and in particular if they have holes in their middles, then the focus should be adjusted. For a full description, see section :

1. Focus the telescope without using a filter.
2. Acquire a star on the autoguider.
3. Step the focus through a range of values around the nominal focus position (the current one, most likely) using the command:

   GDFOCPOS value

   After each step, press FIELD, then WAIT on the Autoguider Panel. Do not leave the autoguider integrating, as the images will get mixed up. Inspect the star image and measure its width with the Grinnell PROFILE function; find the value for which the image is narrowest.

4. When you have discovered the correct focus, type:

   SETGDFOCUS value

   where value is your best focus in mm.