Erroneous Pointing, Limit Switches

Thursday, June 29, 2017 10:58 AM

Problem(s) Encountered:

By our fault entirely, we attempted to point at a target below the horizon

and the TCS entered some sort of safe-mode. The telescope was pointing

horizontally at the control room, leaking liquid nitrogen, and the TCS

wouldn''t turn back on. It was early enough that we could get Eric on the

phone and he talked us through regaining control - we had to hold down

Start  while using the paddle to point to zenith. After that, it took some

fiddling to regain pointing, but we got it eventually. Then, we parked the

telescope, topped off the dewar, and continued our program without

any problems for the rest of the night.


Telescope drove itself into a hard limit.  Power to the telescope is cut at this point as a precaution.  In order to back out, the observer needs to know what direction is safe to move (in this case, south), then move the telescope out of the limit while holding down the green “GO” button on the TCS console.  This is best performed while someone is also physically in the dome watching as the telescope is moved.  Once back at zenith, the telescope positioning should be zeroed using the tilt sensors, then zeroed again on a bright star (near zenith).


Yow, sounds alarming!

The TCS "shouldn''t" try to aim below the horizon -- again, this is one of those flaws that will hopefully*

go away with the installation of the new TCS. (Thorstensen)