Here you can control periodic error management functions, focus positioning, reticle brightness, and mount backlash.
PEM ON: Press this button to turn on the mount’s periodic error correction logic. Before doing this you should do a PEM Record on a night of steady seeing. Once pressed the Last Sent edit box will be updated.
PEM OFF: Press this button to turn off the mount’s periodic error correction logic. Once pressed the Last Sent edit box will be updated.
PEM Record: Press this button to start a PEM record. Typically you will want to wait until a night with relatively steady seeing for your area. Have a CCD camera autoguiding on a relatively bright star (mag 6+) near the meridian and declination 0. Once pressed the timer is activated. Once you are sure the PEM is done (7-8 minutes is adequate) then click the Stop Timer button. PEM is ready to use by clicking PEM ON.
With this control panel
you can control the in and out movement of your focuser. To use this function
you must have an electric focus motor plugged into the focuser port on
your GTO Control Box. JMI,
Meade and others make such a focuser.
First, select the rate, fast or slow then press the "+" or "–" button to adjust the focus. Note: The selected rate will override the keypad’s rate once one of these buttons is pressed.
Quickly pressing the “+” (or “-“) button will send a pulse about 40 milliseconds in length and change the position by 1 unit if in slow mode and 100 units if in fast mode. If you keep pressing the button then additional pulses will be sent. The pulses will accelerate as you keep pressing.
Note: 100 position units in slow mode is NOT necessarily equal to 100 position units in fast mode. That is dependent on the hardware.
You can reset the counter by pressing the “Reset Pos” button.
Note: Because there is no direct correlation between the rates of the fast and slow modes the position will automatically reset to 0 if you switch between Fast and Slow focusing modes.
You can adjust the brightness
of an illuminated reticle with this control. First, plug the cord of the
reticle into the connector on the GTO Control Panel. Press the + button
to increase reticle brightness and the – button to reduce brightness.
One click of the button will change the brightness by one level up to
the maximum or minimum brightness.
This command sets the
amount of backlash compensation employed each time a servo motor axis
reverses direction.
Set Dec: Clicking this button sets the Dec backlash of the mount.
Set RA: Clicking this button sets the RA backlash of the mount.
Click the Backlash Tests button to bring up three tests suggested by Roland Christen to test the health of your declination axis. Roland posted some tests that you can run on your AP mount to see if it has a potential problem with Dec movement.
IMPORTANT: Before running tests 1 and 2 set the mount’s backlash to 0. Also while performing the tests do not try to auto-guide.
Dec Backlash Test 1
Before starting Test 1 set up your camera control program (e.g. MaximDL, CCDOps, etc.) to do a 100 second exposure (but do not autoguide). You can also set up an auto-dark exposure, but make sure that you start the test when the camera control software is exposing the light image.
Once you start the exposure press the “Start Test 1” button. With the default settings (recommended) the entire procedure will take about 90 seconds.
Test 1 will move the scope in this manner: East - pause - West - pause - East to center - North - pause - South - pause - North to center.
The stars in the resulting exposure should look something like the image above. The scale might be different but you should see what looks like many plus signs in the image.
If you take the image near Dec=0 the height and width will be about the same. Although not shown in this particular image the East and West points will be slightly brighter than the North/South points. This will make it easy for Roland Christen to establish the orientation of the camera.
Dec Backlash Test 2
You will run
Test 2 three times, once for each of the guide rates. Before starting
this test set up your camera control program (e.g. MaximDL, CCDOps, etc.)
to do a 25 second exposure but do not try to autoguide. You can also set
up an auto-dark exposure, but make sure that you start the test when the
camera control software is exposing the light image.
Start by setting the Guide Rate to 1x. Once you start the exposure press the “Start Test 2” button. With the default settings (recommended) the entire procedure will take about 16 seconds.
Although the scale might be different, the stars in the resulting exposure should look something like the image shown.
For reference the actual movement in Test 2 is: North+West - South+West - West only (the pause setting) - North+West.
Now you will need to repeat the tests at 0.50x and 0.25x. The star patterns will look similar but smaller because the movement rate is slower. Here are two examples taken with my Traveler:
1.00x:
0.50x:
0.25x:
AFTER RUNNING TESTS 1 AND 2
If you see star patterns different from the above images then crop a bright star in each of the four images and save them as a high-quality JPEG. Please make sure to “stretch” each image appropriately so that it is not too dim or overexposed. If you do not know how to stretch and create a jpeg then save the cropped image in FITS format.
Then send the 4 files (preferably zipped to save bandwidth) to Roland Christen at chris1011@aol.com.
After submitting these tests AP will advise you if anything appears anomalous and if so what can be done about it.
Dec Test 3
This test
moves the declination motor at regular intervals to check that the gears
move properly.
To do this test you will need to remove the cover from the declination motor housing (contact Astro-Physics for directions if you need).
The Guide Rate combo-box has 4 choices: 0.25x, 0.50x, 1.00x, and Cycle. You can choose a specific rate or Cycle to have PulseGuide repeat the test at each rate.
While watching the uncovered declination gears click the Start Test 3 button. PulseGuide will send 5 pulses spaced 2 seconds apart (or however many you entered in the Pulses edit box). Each pulse will be of the same duration – that which you enter in the Pulse Duration edit box. 133 milliseconds is the default. Watch carefully to make sure the pulses look evenly timed and that the fastest moving gear moves equally each time.
Once all pulses have been sent in one direction, an equal number of pulses are sent in the reverse direction. It is normal on reversal of direction that there is a slight delay in movement because of backlash. If this happens you may wish to increase the pulse count.
If you see erratic movement please contact Astro-Physics for instructions.