===== G1 =====
=== MKIII Grating Synchronization Relation (ref GS) ===

This routine records scans, with the standard lamp on, at different step-numbers to collect the necessary data to determine the relationship between the two spectrometers.  RD_GS is used to reduce the data collected in the sgdddyy.### file to give the values of GS and GI needed.

 Uses slit 1