Sequence aborting when PHD2 reports "calibration varied unexpectedly"

When calibration varies unexpectedly - which I think means that PHD2 was looking for, say, 7 pixels per second on each axis and got 7 on one and 4 on the other - PHD2 pops up a message that reports that. What does SGP do then? Lately, since I’ve been there when this happens, I’ve been telling PHD2 to use the prior calibration, since it was good. But sometimes, like tonight, SGP then reports that PHD2 couldn’t be started and aborts the sequence. What should I do to avoid that? SGP log is linked below. The issue came up around 9:51pm.


Hi Kevin,

If you have a known good calibration, why not just use it? In other words select the “Auto restore calibration” option in PHD2 so that PHD2 does not recalibrate at all.

I think it is generally a good practice with PHD2 to explicitly calibrate once near declination zero then reuse that calibration. It is helpful to review your calibration manually to ensure that it is valid (Tools => Review Calibration Data). Then, once you know it is a good calibration, keep it and do not recalibrate. If you have PHD2 recalibrate automatically during your sequence, you run the risk of getting a bad calibration – many things can go wrong … clouds, bad seeing, mount glitch, etc. etc. Once you have a good calibration you should keep it!


Thanks Andy. (And sorry for the late reply - I’ve been off the grid about ten days.) You’re right, I should have started doing that ages ago!