For automation, observing efficiency, and safety of both telescope and personnel, the electronic acquisition of dome azimuth is necessary. Presumably, new telescope domes are designed to be encoded reliably and inexpensively, but an older telescope like the 2.1-m Otto Struve Telescope (OST) may not be so easily retrofitted. The drive cable can slip in its sheave or slide through the grip blocks on the dome perimeter, preventing simple encoding of the motor or cable. The only available location for encoding the perimeter is the tight space shared with the dome rail, wheels, drive cable, and high-voltage slip rings. Maintenance and repair procedures, radial and vertical variations in the dome as it rotates, grease and oil drips, monsoon rains that penetrate the base of the dome, and even insects have foiled previous attempts to use this location for barcodes, radio tags, and possibly contact rollers or a switch system. A global positioning system requires multiple antennas outside the steel dome with the added risk of lightning strikes.