Wednesday, August 4, 2010

the plot thickens.....

since weather cut us a bit short on the previous try, i redid the test of leaving the telescope open, but parked in a fixed position while taking images of the sky to measure the actual pointing position. this time we pointed SALT to an azimuth of 180, locked the tracker at (0,0), and took data for about 8 hours. the air temperature was not changing quickly during this time, though the wind did kick up considerably after about midnight UT. the behavior in elevation is similar to the previous test. the azimuth behavior, however, is rather surprising and i'm not sure what to make of it.

what is clear is that there are significant drifts in pointing that occur without anything happening mechanically with the telescope. i suspect they're related to temperature changes and/or radiational cooling. i also suspect that they'll be difficult to model and predict accurately.


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