SALT: Active control of the primary mirror with inductive edge sensors

The Southern African Large Telescope (SALT) is a 10-m class 91-segment fixed altitude telescope located at Sutherland, South Africa. The segment alignment is maintained by inductively coupled sensors mounted on Sitall brackets beneath the segments. An extensive period of testing in environmental chambers and on the telescope has been conducted to establish the stability of the sensors and their response to temperature and humidity variations in the telescope chamber. We present some of the test results, including a demonstration of the ability of the sensors to maintain the alignment of the primary mirror over a period of 6 days.