The core technologies are IR filter (to increase contrast) + an optical modulator + a synchronous detector (lock-in amplifier).
There are a bunch of variations (mostly, I think, to avoid patent infringement). The basic idea is to have a sensor offset from the optical axis of a telescope (and revolving around the OA--or, more commonly, to rotate the OA about the sensor). The telescope is focused at infinity.
Then modulate the entire field in various clever ways (to avoid the gradient of the sky brightness from affecting the measurement), and detect the total field brightness with a PMT (nowdays you'd use a CMOS sensor or photodiode).
They typically include a servo to point the telescope OA at the star (conveniently, this also tells you how the star is oriented relative to the body axis of whatever the tracker is mounted on).
This is probably the best one: https://patents.google.com/patent/US3165632?oq=%22star+track...
The core technologies are IR filter (to increase contrast) + an optical modulator + a synchronous detector (lock-in amplifier).
There are a bunch of variations (mostly, I think, to avoid patent infringement). The basic idea is to have a sensor offset from the optical axis of a telescope (and revolving around the OA--or, more commonly, to rotate the OA about the sensor). The telescope is focused at infinity.
Then modulate the entire field in various clever ways (to avoid the gradient of the sky brightness from affecting the measurement), and detect the total field brightness with a PMT (nowdays you'd use a CMOS sensor or photodiode).
They typically include a servo to point the telescope OA at the star (conveniently, this also tells you how the star is oriented relative to the body axis of whatever the tracker is mounted on).