Could really do with some help....
I've always tended to get poor DEC guiding with my EQ5 pro mount, with large transients occurring every 10 mins. In trying to understand the behaviour a bit more, I ran the PHD2 guiding assistant recently for an extended period. As the GA disables guiding (so just allows RA tracking with no DEC drive at all) you would tend to expect a fairly straight line response drifting up or down depending on the PA error. Alas, not with my mount. I get a near perfect sine wave of period 600 secs - which suggests that the guidecam is picking up movement in the DEC axis corresponding to the periodic error of the RA drive. With guiding then enabled, PHD2 makes a pretty decent job of dealing with the RA periodic error, but unfortunately doesn't seem to be able to cope with the DEC axis, where clear residual transients still remain.
Would welcome any pointers to what could cause the RA axis drive to affect the DEC axis.
Logfile:
https://openphdguiding.org/logs/dl/PHD2_logs_djAe.zip
Top pic - Analysis of unguided section
Bottom pic - Guided section (from 0100 hrs onwards)
Equipment: EQ5 pro mount, ASI mini guidescope & 120mm camera. Z130 (5" f5 reflector) scope, Canon 500D imaging camera. Mount controlled using ST4 connection.
Rig levelled & balanced, PA using Sharpcap.