Inclinometry on the evening of 970412

Summary : partial CW inclinometry following the welding of track joint 7/8.

Inclinometry started at 19:00 - mean temperature of antenna legs 4.7, falling to 3.5 at end => an average of 4.1C.

Only the azimuth range 10 - 260 was covered. This does not allow a new model to be created, but allows some comparison with yesterday's results. Further changes are seen, particularly at azimuths 139 ( TX and LY) and 220 (RY) where wheels 4 (front left) and 3 (back left) traverse the joint 7/8. (NB : the plot scale is in mV, where 20mV = 1" approx, and no removal of linear baseline (zero-points drift) has been performed).

The differences are typically of order 0.5". I'm surprised that differences continue to appear if they arise as a result of continuing 'settling' of the weld work. The alternative interpretation is that these are random changes, and so far this year we have seen worse occur on a nightly basis.

I expect that the 970411 model will suffice until the next welding and inclinometry, but would appreciate further data should the opportunity arise. TOs please note that current instructions are available via the POINTING link on the JCMT web page.

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imc 970413