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Paramount
GT-1100S
setting slew limits in RA
The Paramount
GT-1100S like the
Paramount ME both have physical hardware stops and also
smarter user definable software limits to protect the Paramount
from hitting itself.
Normally the optimal slew limits for the GT-1100S are
factory set by Software
Bisque before the GT-1100S ships. And the same is true for
the
Paramount ME but here the limits need not be altered. However, if you wish
to check the Paramount GT-1100S limits or alter these slew limits this document
is geared (pun intended) toward
exactly
how this is done.
If you wish to
set your own limits
first reset the default limits to the GT-1100S then
accurately set the gap
specific to your GT-1100S. It is also a good idea to
"BACKUP" your existing settings first!
Before making any changes to
the control system parameters first ALWAYS make a back up!
This is quite simple to do.
You can easily
backup the existing control system parameters by "Saving"
them to a file or copying the text to the clipboard and then
Edit | Pasting them into another application like Microsoft
WordPad, NotePad, Word, and so on.
Backup
the control system parameters here
Save or Copy them to the
clipboard
There is no
need to alter the DEC axis software limits. Leave them
at their factory default values.
When the
proper RA software limit has been set
hitting the hard stop
and causing the mount to become stuck is not an issue.
In this case the mount is smart enough to simply "STOP"
tracking on its' own when it nears the hardware stop. Yes, if this occurs during a
long exposure that will ruin the image.
Correct
soft limit - a bit too large
There must be a gap here
above
the above is a bit large
The above
image shows a very conservative GAP set by the software
limit in RA. This gap is a bit larger then it needs to
be for clarification. See below on
how to set an appropriate size
gap using an American currency dime (~1.35 mm) is
perfect.
In order to reset the
Paramount GT-1100s to the default settings (including slew
limits) use Telescope | Options | More Settings to access
the following TheSky TCS dialog.
TheSky TCS dialog
Press the Defaults button
highlighted
NOTE: The Mount ID: above will be identified as the
Paramount GT-1100S!
IMPORTANT: If
nothing appears to happen when you press the "DEFAULTS"
button above it is very possible and most likely that
the following "Reset to defaults" dialog does not have
"focus" i.e. it is not visible. That is the dialog is not in front but behind
another
dialog being hidden.
I have seen this!!
Press the Windows option "ALT+TAB" until you can see the
dialog “RESET TO DEFAULTS”. TheSky will not allow
you to do anything until you close the dialog. If it
is not being displayed then it will seem as though you
cannot do anything!
DO NOT
REBOOT! Just find the dialog
using the Windows "ALT+TAB" to switch tasks and pick the Paramount GT-1100S when the "Reset to defaults" dialog appears.
The following will appear
Choose Paramount GT-1100S
Accessing the Slew Limits
Note the RA limits on the
Homing/Limits dialog
WARNING! DO NOT
use the "START" button to home, stop tracking and clear
current limits with the GT-1100S.
First reset the slew limits to
their default values as per the above. The following
image shows a very
reasonable size gap that will work very well. The
thickness of a dime (~1.35 MM) between the RA hard stop and
the bolt in the RA shaft.
Good size Gap for RA 1.35
mm
Thickness of a dime 1.355
mm is just
right!
If you cannot move the
GT-1100S into the proper position using the Joystick as
shown above you will have INCREASE the RA limit. By
making the current RA limit a larger value you will be
allowing for more travel. Try adding a small amount
rather than a large value to avoid driving the RA axis into
the hard stop. See below.
WARNING!
Once
you have increased the RA limit (~50 counts) to
allow for more RA travel it becomes possible to
HIT the
hard stop. If you are not very careful (move
slow!) you will go too far and hit the hard stop causing the
RA axis to become stuck and the control system will be
beeping.
See below for details on
how to
remove the stuck RA axis. This is merely
inconvenient and will not cause any damage. Just
position the RA axis off the stop and re-home the mount to
try again.
TIP:
You can use the RAW encoder values reported by TheSky TCS
dialog to accurately set the RA limits specific to your
own mount. One side uses a positive number the other
negative.
First carefully move the GT-1100S in the RA axis to the proper
position (WITH TRACKING DISABLED) then use the "Status" tab
shown below to see exactly what encoder value is reported for the RA
axis in this position. This becomes the new more
accurate RA limit. There is one positive value and one
negative value depending on the side of the meridian the mount is
currently
on.
Hint:
First disable the tracking of the mount or the encoder value
will continuously be changing as the mount tracks.
Disabling the tracking makes this much easier.
To disable
tracking use Telescope | Options in TheSky and remove the
check mark next to "Tracking". This is a toggle
enabling or disabling the tracking state. When
tracking the mount is moving and the current encoder
position is constantly changing. When disabled the
current encoder position will stay nearly the same number +-
a digit.
RAW encoder values
Use the RA Current encoder
value to set the limit
Above the new value for the RA
slew limit -312056 corresponds to the RA axis in the
correct position very near the hardware stop but not
touching see below.
When the side with the
negative number is set flip the mount over and follow the
same procedure for the positive side.
Note the
following image shows a position where one of the RA software
slew limits
allows too much travel in RA causing the RA axis to
physically hit the hard stop. For example, this can
happen when the Paramount is left tracking to the meridian when
the RA software limit on the west side of the meridian
(northern hemisphere) is not optimal. There is too
much travel being allowed in RA because the
slew limit value is
too large.
This will not work!
RA bolt cannot be allowed to hit the hard stop
If the above
position is reached the RA axis will become
physically "STUCK" on the hard stop. There is no way
to recover from this without manual intervention. The
Paramount GT-1100S will simply shut down (no harm done) but homing
will no longer work and the control system beeps
constantly indicating that there is a problem.
Recycling the power will not solve the problem either.
If the telescope is REMOTE as is the
case
with GT-1100S in Chile where there is no one on site
this would be devastating.
WARNING!
The only way
to recover from the above position (hitting the hard stop)
is by removing the RA worm cover and manually turning the RA
worm to free the RA axis. See below
instructions for freeing a "stuck" RA axis.
NOTE: This would be
catastrophic for a remotely installed Paramount GT-1100S
where no one is on site to fix the problem, like the
GT-1100S in Las Campanas, Chile.
When the RA axis becomes
physically stuck on
the hardware limit you must remove the RA worm cover and
manually rotate the worm to "free" the RA axis from the
hardware stop. See below.
Manually rotate the worm!
The worm will move easily
If you like you can also
firmly grasp the belt to help rotate the worm. The
worm will need to be rotated either clockwise or
counterclockwise depending on which side of the meridian the
mount is on and the hemisphere. Use the trial and error
method.
Once the RA axis has become
freed HOME the mount for normal operation. At this
point go back and attempt to set
the proper gap in RA.
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