The diameter of azimuth disk is 1174.72mm, altitude is 1268.21mm.
At round about D disk =1200mm, 1arcsec conforms to 2.9µm on tape. 1 sec tracking at sidereal rate conforms to 0.0436mm on the tape.
The magnetic tape has a pole length of 1mm and the read head is MK1-2k-R.
That should give a maximal resolution of 0.5µm.