@legnol: Here's the way things work, as I understand them:

The internal guider in Ekos, in order to be able to correct guiding errors, needs to know the effects that DEC pulses it sends to the mount will have on the DEC motor. It gets this information when calibrating. That is, it pulses the DEC motor, and sees which direction and how far a given guide star moves.  When the calibration is saved, whatever was measured is stored and reused later. However, some mounts are tricky and change the direction a dec pulse moves the dec motor, depending on the side of the mount. The internal guider needs to know if the mount is being tricky in this way. That is the function of the checkbox labeled "Reverse DEC on pier-side change when reusing calibration."  If the box is checked, the internal guider negates the pulse it thinks it should send, if it is on the opposite side of the pier from where it was calibrated.

The proper setting for that checkbox depends on your mount. You can find out the correct value experimentally:  Calibrate in a nice spot (e.g. a bit west of the meridian near the equator), guide for a while making sure you have some DEC corrections, (it should work), slew to somewhere else on the west side, (should still work). Now slew to somewhere on the east side. If it still works, great, you guessed the right value for that checkbox. If not, repeat the experiment, but this time use the other value for the checkbox. Hopefully it will work this time.

There is a very similar checkbox in PHD2, for the same reason. It is explained in the PHD2 doc here:  openphdguiding.org/man-dev/Advanced_settings.htm Search for 'Reverse Dec output after meridian flip'.

Hy
 

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