6.5. Fibre Calibration. The system has variables to control the size and origin of each of the Fibre bundles. Each Fibre is described by the variables fWX0, fWY0, fWX and fWY where f is one of the letters G, P, F, C or S for the Guide, Probe, Fine, Coarse or Slit fibres respectively. One procedure for calibrating the fibre positions is to select the CASS application with the appropriate CCD head, say UES:

0 APP 1 HED and perform a 8 FLD acquisition with light coming down the fibres. This will show up the fibre positions. Hopefully the star log will display the centre of each of the fibres. Check this by moving the tracking window to the centre position of each fibre in turn, changing its size to be the same as the fibre of interest, and displaying the tracking window border. For example: 8 FLD 126 135 WMO 40 WSZ SHOW-TWIND will place a 40x40 window centred on (126,135). Once this window is judged to be in the right place, display the fibre parameters with SHOW-FIBRES, then LOCATE FWX0 and edit that block to store the new parameters for future use. Future versions of the software will have a much easier way to set windows.