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Slaving dome to telescope #2
Attendance: Gabriel
Date/Time: 12/13/2022, 20:30 -12/14/2022, 00:25
Spaces Occupied: Control Room, Dome
Goals:
Slave the Dome to the telescope
LOG:
Skip to first note for solution...
- During some slews of the telescope with the dome "slaved" to the telescope, I noticed that in the DFM TCS software the dome thinks it has the same azimuth as the scope, even though it is over 70° away.
Upon manually getting the dome aligned with the scope the first time, I notice that DFMTCS thinks the telescope's azimuth is 164.7 while the now actually aligned dome's azimuth is 250.0. Below I have made a table with all my attempts.
Try# Scope Azimuth Dome Azimuth
(Manual Tracking)
Difference
1 164.7 250.0 85.3 2 4.5 69.6 65.1 3 58.7 132.6 73.9 4 127.5 205.0 77.5 5 299.2 6.3 67.1 - I can't say with certainty that there is a pattern in the differences of the (perceived) azimuths, and I won't get any more data to confirm or deny this for now (too time consuming to do alone) ,but there might be a linear (ish?) correlation between the percentage differences of the azimuths based on either the position of the dome on the circle
, or just based on the overall rotation of the dome. If the latter is true, then it is very likely that the belt on the rotation measuring motor (lack of a better word, please edit to fix) is missing some teeth, or the motor itself has faulty sensors. Inspection needed.
- Upon further inspection, the belt is perfectly fine and so are the gears that the belt latches onto. The Gear that gets turned by the dome's rotation, which then turns the motor that measures the rotation, also seems fine. The problem now seems to only be the motor itself, or the gearing system.
- We can prove the gearing system being at fault if we can measure the % difference of the azimuths when starting at a fixed point. We will do this by slewing the telescope into some arbitrary azimuth/angle number (will call this number d), with starting point 0. The dome will be manually slewed into the correct position over the telescope (while the telescope is still at 0 azimuth). Now we will slew the dome over the new telescope position and we measure the percent difference in their azimuths (don't forget to count full circle rotations too if the total in rotations is bigger than 360°). Repeat a couple times.
- I know that this could mean that there is either a gearing problem or possibly a hall effect sensor problem in the motor.
These are some more experiments that I did. I will not continue them today as they are taking a long time since I'm by myself
rotation# Scope Azimuth Dome Azimuth Scope
%
Scope%to
Dome%
Dome
%
0 0 45.8 - - 1 30.0 72.9 0.6282 2 60.0 111.2 0.5 0.7959 0.6555 3 92.9 148.2 0.6666 0.8884 0.7503 4 120.0 175.8 0.75 0.8896 0.8430
BIG NOTE: issue is fixed, the problem was caused due to the plastic gear which was driven by the dome's rotation (and connected to the motor) not having its screw securely tightened. I tightened it and then aligned the scope with the dome. Then I went into DFMTCS → Telescope → Initialization → Other positions and then set the dome azimuth to the scope's azimuth. The tracking is off very slightly to the right side by a negligible amount (the scope is still almost centered), but it remained the same on all of my many tests. I believe this might be due to my own imperfect calibration, but it still shouldn't be a problem.
NOTE: HALT MOTORS BUTTON MIGHT BE MALPHUNCTIONING; I PRESSED IT TO SEE IF IT ACTUALLY WORKED AND THE SLEWING STOPPED FOR A SECOND AND THEN SPED UP MORE THAN BEFORE (???). It is possible that it only seemed to me that it sped up, but the motor pitch seemed to increase. The slewing didn't stop though, but the cancel button or cancel command both work.
NOTE: When slewing the telescope there seem to be some azimuth ranges that it skips over. The one I discovered is 87.1-92.9 (I don't seem to be able to slew the telescope in any of the values in between). If this is an actual issue, could this be causing problems like that?
NOTE: THE DOME DOORS WERE CLOSED FOR THE ENTIRE DURATION AND EVERY TRY WAS RECORDED FROM THE CAMERA. THE VIDEO FILE CAN BE FOUND EITHER IN BLUE IRIS OR C:\BlueIris\New
TODO:
- Test the dome tracking again, in case every attempt was a fluke (unlikely)
Direct Questions/Concerns to Roy Prouty (roy.prouty@umbc.edu)