Re: 3600GTO - El Capitan unveiled at AIC


Wiggins, Rick
 

Hi Roland,
I expect that if you are operating your mount manually or through a
simple planetary program, you may not ever have the mount get lost.
However; if you operate remotely in an automated environment, you are
going to have the mount get lost. There are so many indeterminate
failure modes of all the software and the computers, that it is very
likely that you will have this happen. It has happened twice to me.
Once when a Windows error caused a freeze and then reboot during the
night. A second time was when an error between two programs stopped a
CCDCommander action and the mount eventually hit the pier. Both
instances caused the mount to hit the pier, clutches to slip, and
mount to get lost.
Thanks, Rick

--- In ap-gto@..., chris1011@... wrote:

In a message dated 11/21/2007 12:33:32 PM Central Standard Time,
egroups@... writes:


The purpose of the homing feature is simply to establish the alt-
az
position of the mount. Once you've established that, the mount
can be
driven as usual afterwards. I don't see why homing sensors are
logically any different than resuming from a known "park"
position.
(Except, of course, with the homing sensors, you have a true
hardware
indication of the known starting point.)
The mount already always knows where it is, so no homing feature is
needed is
everything is operating correctly. The Alt-Az position of the mount
is always
known in the servo, even when the power is removed - it is known to
a very
high precision. The only purpose that I can see for a homing
feature is in
situations where the mount is lost due to some kind of glitch. If
the mount is
really lost and does not have it's alt-az bearings, it will not be
known which way
the axis should rotate - east or west - in order to pick up the
location of
the sensor. If it rotates the wrong way, and the mount has the
ability to go
beyond the meridian, then it can very likely run the telescope into
the pier in
its effort to locate the sensor. Therefore, for this kind of
operation we
woudl need to configure the mount the way everyone else does it and
remove the
ability to run past the meridian.

In my case, in all the years that I have run my observatory, I have
never had
the mount get lost, with the exception of times when I have used
Sync with
the scope past the meridian. The mount really was not lost, it was
just
reconfigured with the counterweights now pointing at the object and
the telescope
doing counterweight duty. In the future we will develop a system
that will allow
full 360 degree operation for the mount without the limitations of
a normal GEM
- same as a Fork mount. There are still a couple of things to be
worked out,
mechanically and software wise, before we can offer this
configuration to the
users. In that case, a homing feature can work nicely, but for what
reason I
still am not clear.

Rolando


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