Date: Mon, 22 Mar 1999 10:21:20 -0800
From: Russell E Owen
Subject: Re: 3.5m Night Log 990320
> * There was a repeat of the problem described yesterday during stow
> procedures; since it now appears to be repeatable, I detailed it in
> a problem report. Another interesting matter came up, however. This
> time, when the alt motors began to complain, I issued an "axis
> stop" to stop the telescope, which seemed to work. But when I sent
> a new rotate command, the azimuth and altitude axes both started
> moving as well. This sounds like a potential problem.
track/stop apparently only handles the azimuth and altitude. I hadn't
realized that when I recommended it, but it makes sense in
retrospect. It can easily be fixed.
At present TRACK/STOP halts az and alt and nulls out the object
coordinate system. It was never designed to handle the rotator.
However, if the rotation type is object or horizon then nulling the
object coordinate system is sufficient to halt the rotator. I can fix
it so that TRACK/STOP intentionally halts the rotator, as well, and
nulls out the rotation type.
Regarding overshoot: TRACK/STOP intentionally stops the telescope
right where it was when you issue the command. As a result there will
be overshoot. AXIS STOP has the same property, but it is faster, so
the overshoot will be smaller.
Regarding axes restarting: a rotate command will restart halted axes
unless you specifically request otherwise. This is the documented
behavior, but in retrospect is not the obvious behavior. I originally
programmed it to match the TRACK command (which also restarts halted
axes by default). I will change the default for the ROTATE command.
Changing TRACK/STOP to halt the rotator and ROTATE to not restart
axes will be easy, but finding time to make the changes will not.
Until I can get to it, I recommend:
- use AXIS STOP or AXIS INIT to halt axes
- use ROTATE/NORESTART to move the rotator if you want to be sure az
and alt won't start moving
Regards,
-- Russell