GPUSB/Gemini stopped working in RA but not DEC

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asimen
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GPUSB/Gemini stopped working in RA but not DEC

Post by asimen » Mon May 09, 2011 8:05 am

My system has suddenly stopped working after about two years of flawless tracking.

I have a Losmandy G11 with Gemini Level 4 and a Shoestring GPUSB connected to the
AutoGuider port, and I have my computer connected to the Gemini system through a USB
to serial converter interfacing to the RS-232 port on the Gemini. I am running Gemini
Telescope.Net Version 1.0.0, Maxim DL Version 5.15, MaxPoint version 1.0.20, Robofocus
Version 3.2.3, PHD Guiding Version 1.10.0, and FocusMax Version 3.2.1 on a laptop
running Windows XP Service Pack 3. I have a Maxon motor running the RA axis and an
older motor running the Dec axis.

Two days ago I found that I was unable to perform autoguiding calibration in PHD Guiding
and consistently obtained the error "RA calibration failed - star did not move enough". I
tried to increase the calibration step to 2000 and 4000 ms but this did not help.

I tested the GPUSB unit with a multitester according to instructions that I obtained from
Shoestring. All of the pins were found to go high or low correctly as a function of RA/DEC
signals. I initially tested the unit where the RJ-12 connector bumps out of the GPUSB unit.
To test the RJ-12 cable, I also tested at the end of the cable, at the connector which plugs
into the Losmandy autoguider RJ-12 connector, and again obtained correct high/low
values for each RA/DEC signal. Therefore, the GPUSB and the cable seem to be OK.

When I use GPUSBCheck and I observe the RA and Dec values on the Gemini
Telescope.Net application, I can get the Dec values to move appropriately using the
Dec+ and Dec- buttons on GPUSBCheck. However, neither the RA+ nor the RA-
button causes any changes in RA. I repeated the test with the mount completely
unloaded, with no telescope on the mount, and obtained the same result.

The mount will slew correctly to objects in the Maxim DL database as well as with
the hand controller. The mount will also track stars accurately. Therefore, the RA
and DEC motors are working correctly. I have verified that the Gemini is in Photo
mode and that the hand controller is set to tracking. I have tried to reboot the
Gemini system and the computer and I have checked all of the connections multiple times.

This seems to suggest that the Gemini hardware has stopped responding to RA but not
DEC signals. Where do I go from here?

Any help would be much appreciated. Thanks very much!

dpanderson
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Re: GPUSB/Gemini stopped working in RA but not DEC

Post by dpanderson » Mon May 09, 2011 9:05 am

You could test the guide port of the mount completely separate from the GPUSB and cable. Should this test fail, then you would know for sure that there is a failure within the Gemini hardware.

If you short pin 2 (the common pin) of the guide port input to pin 3, you should see movement in RA. Repeat with pin 2 shorted to pin 4, this should produce movement in Dec, pin 2 to pin 5 should produce movement in Dec, pin 2 to pin 6 should produce movement in RA.
Doug Anderson
Shoestring Astronomy
http://www.ShoestringAstronomy.com

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