Using automatic Focus Adjustment at Prime

The Prime focus CCD software allows automatic compensation for the changes in focus due to different filter thicknesses. This option must be explicitly enabled with the SETFOCUS command.

1. Use the ADAM command WHEEL to set up a table with filter thicknesses (see the Prime Focus manual section 3.1).
2. Make sure that the same filter is used for which the focus was determined. Alternatively, determine the focus now for the current filter.
3. To enable the focus adjustment, type, before changing filter:

   SETFOCUS value

   Here, value is your best estimate of the focus, in mm. The focus will be driven automatically to the correct position on change of filter.

4. To disable the focus adjustment, type:

   SETFOCUS DISABLE

Beware of starting an observation until the focus has stopped driving and the red focus stop lamp on the Control Desk is lit.