REFRESH TIMER EXCEPTION with disconnect mount

[Takanori Sakamoto]

Hi,

I'm having "REFRESH TIMER EXCEPTION" error once in a few month. The telescope mount is disconnected after this error. If you just try to re-connect the mount, the telescope altitude and azimuth values start to change although the telescope is not moving (detail later). To get back to normal, I need to reboot the machine. After the reboot, everything goes back to normal.

The error message in the ACP Console is:

REFRESH TIMER EXCEPTION
SourceriverHelper
Overflow
Phase=2

Since a robotic nature of our telescope, we are not disconnecting the mount and the camera (no "shutdown" command is used at the end of the plan). The mount and the camera are both connected all day. I'm extracting the telescope ra,dec,al and az information along with the CCD temperature using the ACP web interface (I have asp file sending Telescope.RightAscension, Telescope.Declination, ... commands to get the information). All time connection is importatnt for me so that if something goes wrong with the machine (or the mount and the camera), my monitoring script will beep me immediately. I'm getting the telescope and the camera information every 5 min.

Attached is the status plot (this plot is created using the information which I mentioned above) of our telescope when this error happned. The top two pannels are rain sensors and dome status. The 3rd panel is the CCD temperature. From 4th to 7th panel is the telescope ra, dec, al, and az information. Time is EDT. I got the beep that the ACP is not responding at ~11:30 AM (you see a blank period in the plot). Indeed, the mount was disconnected with the "REFRESH TIMER EXCEPTION" errpr. After ~12:00PM, I re-connected the mount. Then, as you can see in the plot, al and az values started to change, but not ra and dec (Tracking was off). I also confirmed that the telescope was not physically moving (telescope was pointing to the sky even though the altitude value was below 0 deg). It seems like the driver went nuts after the error....

Since the error happened during the day (not during the observation), I don't have any log file recording what happened before/after the error. All I have is the error messages at the ACP console.

I'm not sure whether my all-time connection (not doing shutdown) to ACP is causing the problem.

My telescope mount is AP 1200 GTO mount.

Thanks a lot for your help.

Regards,
Taka Sakamoto