UIST: Engineering: Clearing the Window of Ice

Below are tips on how to clear ice from the UIST window. Ice will be obvious in data: images will be blotchy, while arc spectra will not be continuous vertical stripes.

You can get at the UIST window either from inside ISU2 or by partailly removing the calibrations unit. In both cases, the UIST calibration unit mirror needs to be out of the beam. Login to a computer (any machine at the telescope) and open the uist oper screen in the normal way (dm uist_oper.dl). Then just click on the "Out of Beam" button. You don't need to run the telescope up, nor click on anything else in the uist oper screen. (When you're done, put the mirror back "in Beam" please).

• From Inside ISU2 - Its possible to clear a modest amount of condensation from the UIST window by pointing a hair-dryer at the window from inside ISU2. You may have to move the dichroic N to get at the window. This is quite tricky, though, so if you feel uncomfortable doing this then please just leave it. The down side is you can't see the window from inside ISU2.

• By Partially Removing the Calibration Unit - To remove the calibration unit, apparently there are a couple of screws to be loosened. You would then slide the unit out part-way. You should not unplug any of the calibration unit cables (doing this without powering down is a no-no), nor slide the unit out two far. Once you can see the window, then just go at it with a hair-dryer. This is a TWO-MAN JOB!