Tuning the ServoCAT motors

After the observing session on June 6, it became clear that the ServoCAT motors needed tuning, a task that took a few days to complete.

June 11:

I tried to connect to the ServoCAT using the SCU.exe and ServoCAT-Sky software. Unfortunately, this did not work on my Mac in a Virtual Machine.

June 12:

I brought a Windows laptop from work, and the connection with the ServoCAT worked without problems. I was able to read the current settings:

• Download,AZ,2000,14610,60,140,270,45,120,210,3,1,1,2,0,17500
• Download,ALT,2000,13392,50,140,270,40,120,210,3,1,0,2,50,1000

and firmware version: 70.C.

When I tried to start tuning the motor, I realized that the shaft of the Azimuth axis was missing. Luckily, I found the shaft without any problems, as it was still in the garden where I had previously observed. It took some time to repair. I also ensured the altitude axis was correctly installed, as I had to remove the mirror box. By then, it was too late to start the motor tuning.

Repairing the azimuth shaft of the ServoCat.

June 13: 

Today, I was able to tune the motor parameters. Initially, the GoTo function didn’t work because the USB protocol of the Nexus DSC Pro was set to LX200 instead of ServoCAT (for using the eFinder). Aligning during the day was also challenging, but using a compass and SkySafari to estimate the positions of two stars made the alignment successful.

To tune the motors, a GoTo must be performed over a large part of the sky. I used a GoTo of 173.5 degrees for the azimuth. The GoTo stops before the reading on the Nexus DSC Pro reaches 0.0. Ideally, the first stop should be as close to 0.0 as possible, but in my case, the GoTo stopped 8.1 degrees from the expected location. I adjusted the gear ratio, and the results were much better on the next attempt. I performed a similar exercise for the altitude axis.

Updating the telescope parameters

I also updated the backlash values by observing the encoder readings while pressing the left/right and up/down buttons. Initially, it took a few seconds for the telescope to start moving, but after updating the backlash values, the telescope now begins moving within one second.

June 23: 

I conducted some initial tests under the night sky. The ServoCAT seems to work much better, but there was an issue with the GoTo++ functionality of the eFinder. The telescope did not start moving, and the readings on the Nexus were set to 0.0.

June 24: 

Another clear night allowed me to test everything again. Now, everything works perfectly. I realized that I had forgotten to perform a GoTo on the Nexus before using the GoTo++. This explained why the telescope did not move the previous night. This issue did not occur during the observation on June 6 because I used SkySafari, which always submits a GoTo to the Nexus DSC Pro.