let me say up front that i don’t know if this has anything to do with SGP, but it is the only piece of software that has changed before this problem cropped up:
for some reason, SGP is reporting the mechanical rotator angle differently in 427. my rotator is set so that the home position of 0 degrees is the same as the sky angle of 270 degrees. up until i installed 427 a couple of nights ago, SGP would report the sky angle and mechanical angle as being off by 90 degrees as expected. now it’s reporting a difference of 32.4 degrees.
in addition, PhD no longer seems able to properly rotate the calibration vectors. when changing between targets with different rotations, the star is just driven right out of the guide box. i’m having to calibrate before every target now.
the common piece here is @Andy 's AG Pyxis rotator driver. however, i have not touched this driver in years, nor have i rotated the rotator. it still homes to the 270 degree sky position, and the optec control program (which connects directly to the serial port) says the home position is 0 degrees.
i’m running kind of an old version of PHD2 (2.6.6) but again this has not changed either.
anyone seen anything like this? any ideas what could be wrong?
hm… i think the rotator might be failing. i just noticed while playing with the optec software that it’s getting stuck and slipping trying to home.
i guess if the encoder in the rotator is relative then this could account for the discrepancy between the position that SGP eventually drives it to (correct sky angle) and the reported mechanical angle of the rotator (wrong, due to the various slips and locks)
maybe with the colder temperatures the case shrank or something, i had to adjust the grub screws on the front which apparently control the rotator plate tension.
this has been another episode of debugging in public, brought to you by Duh, the makers of Derp.
yeah, that would explain the symptoms. The rotation of the guider calibration vectors happens on the PHD2 side by reading the rotator’s current mechanical position angle from the rotator ASCOM driver – unrelated to SGP. If the sky angle - mechanical angle difference is changing you’ll get runaway guiding for sure.
yes thanks, that’s what i thought since PHD2 doesn’t depend on SGP in any way that i know of. it was just seemingly that SGP was the only thing i had changed. but the weather changed too.
from time to time the rotator chatters a little bit as it is homing and i guess it was never enough to throw off the mechanical angle enough to mess up PhD2, so i never knew the mechanical angle was derived from the servomotor position. but that makes sense as the cost of an absolute encoder on a rotator would be ridiculous.
well, i’ll recalibrate at the equator again when the weather clears up and hopefully that will hold me for years again.