6.3. Prime Focus Guiding

Having acquired and selected a guide star as described above in section 5.3. start the guide loop with GUIDE ON. A small window will be read out centred on the selected starlog entry coordinates. This should contain the star image, interated for the same time as was used with the FIELD command. The window will track the star if it moves across the CCD, until the star approaches the border of the fibre window, when the guide loop will abort. The only difference between Prime focus guiding and Cassegrain guiding is that the fibre area, where the window can track, is smaller than the cassegrain full CCD field. It is possible to change the integration time, window size and window position whilst guiding at Prime focus.

6.4. AutoFib Guiding

Acquire and select a guide star as described above in section5.4. Remember that the starlog is in two halves, stars 1-8 are in the fixed probe fibre area and stars 10-18 are in the mobile probe area of the CCD. Start the guide loop with GUIDE ON. A small window will be read out centred on the selected starlog entry coordinates. This should contain the star image, integrated for the same time as was used with the FIELD command. The window will track the star if it moves across the CCD, until the star approaches the border of the appropriate fibre window, when the guide loop will abort. The only difference between Prime focus guiding and Casegrain guiding is that the fibre area, where the window can track, is smaller than the cassegrain full CCD field. It is possible to change the integration time, window size and window position whilst guiding in either fibre. The AutiFib application allows either fibre to be read out and centroided independently from the guiding process. Whilst the fibre is being centroided, the guide loop is temporarily suspended.