Hi Rainer,
Drift in ra / drift in dec / or drift compensation to correct
Alignement problems of polar or azimut axis.
You can see Reset, Refine and Set buttons.
Both Reset and Refine buttons start measuring drift. But Reset also switches to sidereal speed (it resets user rate at sidereal speed); refine keeps current user rate unchanged (drift measurement occurs in this case at current user rate).
When drift measurement is completed you can click on Set button to apply the computed drift compensation...
But when is drift measurement completed?
1. On RA axis only after a worm period has elapsed since the click on Reset/Refine (to take into account the periodic error that could affect drift measurement). So you will see a countdown will start as soon as you'll have clicked on Reset or Refine... At the end of the measurement Set button becomes enabled...
2. On Dec you can click on Set as soon as you think enough time has elapsed since the click on Reset/Refine. So you will see a counter will start as soon as you'll have clicked on Reset/Refine. The counter is just meant to show the time elapsed/used for drift measurement...
Then the driver (on Dec) will take care of the time elapsed between the click on Reset/Refine and the following click on Set to compute the drift and the required user rate to compensate it...
The idea is simple: on RA tracking speed could be wrong; on Dec you can have drift because of a not perfect polar alignment.
So the driver, as soon as you click on Refine or Reset, starts to sum all guiding pulses duration.
After one worm period on RA you would expect 0 as the sum (I assigned negative sign to RA+ pulses and positive sign to RA- pulses). But you'll probably find a positive or negative value because of drift. As soon as you'll have applied the compensation the motor speed will change accordingly and in the next drift refinement you should find a lower (ideally 0) mean value of the duration of the pulses occurred during the refinement period...
On Dec the same happens but without a countdown: ideally Dec motor should not move at all while tracking. But if, after a Reset/Refine click and some minutes you see the sum of the durations shown is still increasing (or decreasing) then there is a significant drift that you can compensate by a click on Set. After the click, Dec motor will start moving at appropriate constant speed (it should be small) and you should see that the following guiding pulses duration will show a mean value really small (ideally 0)...
I mean to point out that drift compensation requires the use of pulse guiding (i.e. guiding by ASCOM): ST-4 guiding commands (and durations) can't be detected by the driver...
CS
Armando