[tgsovlerkhgsel]

I assume the constant is usually chosen short enough that the system will "forget" turns quickly, in exchange for becoming useless while turning?

Still, getting this whole thing accurate to probably one minute of arc is insane, especially with the gyro and star tracker linked only via motors and synchros. So the total error is the sum of any deviation of the gyroscope from the actual down direction, the error in measuring the gyro angle, the error in setting the star tracker to that exact angle, and then all other errors the system introduces. Then you need to take multiple separate measurements at different times and compensate for the movement, and a one-degree difference means you're over the wrong city (or in Europe, country) so the end-to-end accuracy must be much better than that.

And sailors supposedly did that with a sextant to something like 0.01° on a moving ship.