My objectives for this session were to begin to reaquaint myself with DSO imaging, and to test and tune the GM8 mount. Ultimately, I would like to be able to use the GM8/TV for DSO imaging while the G11/Meade is set up for other work.
This was an interesting evening. I gained some experience with the camper and cold weather, and I identified at least one mount problem that I was able to isolate, but there may be a second problem.
As for dealing with the weather, I would call the night a success.
My starting point for this exercise was the Farm on 11/4, at which time I found myself uncomfortably cold, and I was doubtful about being able to camp at the low 40s temperatures that we experienced there. After what I have learned tonight, I realize that sitting outside at the computer for several hours on 11/4 manually guiding during planetary imaging was the problem. In short, I had let myself get cold, and I couldn’t warm up.
Tonight, the temperature as 33 degrees when I went outside at 1700 to power up and start up. I was wearing flannel lined pants and my heavy blue parka.
I was outside at the scope for maybe twenty minutes to polar align, and initially focus both cameras. My right hand, which needed to be outside of the glove for the task at hand, got cold, but not horribly cold. Ideally I would have been in the camper for the remainder of the night.
Dealing with the problem(s) that I was experiencing, I found myself outside several times especially toward the end. I was ok for about the first hour or so, but soon felt myself getting cold. I immediately turned up the camper heat, put on ski pants, and put on a sweatshirt inside of my parka. My feet were a little cold, probably because there is little to no insulation in the camper floor. Next time I’ll wear my boot warmers. Other than slightly cold feet, I stayed warm for the remainder of my time outside.
It was 2045 and 26 degrees when I shut down and came inside. My feet were chilly, as was my right hand from being out of the glove. Nothing was too cold though. I feel like I can easily image down to 25 degrees, maybe even 20.
Now for the problem(s) that I had.
I got a strange looking calibration graph. It was almost at 90 degrees near the apex of the two legs. The Dec axis was straight, but the Ra axis curved back toward the dec axis. Not getting a calibration error message, I tried guiding to see what would happen.
The main guiding graph across the bottom of PHD2 was really bad. The Ra line curved increasingly upward while PHD2 was issuing guiding pulses in the opposite direction. The dec axis curved increasingly downward while PHD2 was issuing upward guiding pulses. I was left in with the impression that the guiding pulses where the opposite of what they should be. I checked and rechecked and rechecked mount and PHD settings, and could not find anything that could be causing this.
Eventually I did another calibration run, and this time the orthogonal error was almost 90 degrees, which means that both legs were pointing in the same direction. This could only mean one thing, and that is one axis was not responding to pulses. It turns out that the Ra motor was running without moving the mount.
I believe that the motor spinning without turning the Ra axis is a result me having the drive components taken apart to replace the worm block yesterday. There is a collar with two tiny grub screws that I obviously didn’t tighten enough.
I mentioned that there might be a second problem. I cannot imagine how the loose collar would cause the guiding graph that I was seeing, but then again, I cannot imagine what a guiding graph would look like with a loose collar.
At any rate, I need to fix the known problem (the collar) first, and see if that takes care of the other problem.
This is not something that I can do in the dark, so I shut down and saved the fix for tomorrow.
Other than the Ra drive problem, many things worked great. I was able to remotely connect to the small laptop, connect to all of my components. Assuming that the mount is able to track/guide adequately, I believe that I would have been a little rusty, but I could have gotten an image session going.
All in all it was a good night. Next time out I will not be starting my transition back to DSO from scratch, and I have increased confidence in my ability to manage myself while working in the cold.
One thought on “GM8 Equipment Tuning”
The loose collar grub screw has been tightend, and I am ready to test the GM8 again.