Telescope Motion Failure

Tuesday, January 15, 2013 2:47 PM

Problem(s) Encountered:

The bulk of our trouble was associated with the extremely cold weather, pushing 10 degrees Fahrenheit. The declination drive of the telescope locked up while slewing, which rendered the automatic pointing function of the TCS completely unusable, resulting in a  point failed to converge  error message, in addition to a  point track rates incorrect  error.

After much fiddling, we figured out a viable system for pointing the telescope manually, using a combination of the GUI and physical paddles. After slewing the telescope with the physical paddle until it locked up, we increment in the same direction with the GUI paddle, then continue moving with the physical paddle until the telescope locks up again, then repeat the GUI paddle incrementation. Using this strategy, we were able to successfully point the telescope and track targets.

In the process of trying to resolve the pointing problem, we repeatedly tried to home the telescope. Due to its inability to slew, the telescope would also fail to home properly, resulting in a  ERROR where m_ha not homed  message on TCS (also an ERROR where m_dec not homed message). After eventually homing the telescope manually using our physical/GUI paddle routine, we reset the pointing of the telescope by zeroing the tilt sensors and setting  zero ra=xx:xx:xx dec=+31:57:12 , which convinced the telescope that it was in the home position and re-calibrated the HA and Dec readout on TCS.


This was a combination of the extreme cold and its impact on the Dec preload.  It is bitter cold, and has not warmed above 0C for over a week now. Subtle preload adjustments got the system working more or less reliably.