Preparation during the day

On the observing floor:

Check that the cooling system is operating, and that the indicated temperature is about -20C or lower. The cooler must be switched on at least 3 or 4 hours before starting the observations. This is usually done by NOT staff. The two red switches on top of the compressor on the observing floor under the telescope are switched to ``on''.

Switch POWER ON, CHOPPER ON, and REMOTE CONTROL ON, at the polarimeter (see Figure 3.1).

 
Figure: The polarimeter with it's controls.

Check that the CALCITE PLATE knob is OUT for POLARIMETRY and push it IN for sky-chopping PHOTOMETRY.

Make sure that the SHUTTER is closed, i.e. that the knob is in the OUT position.

In the control room:

Check that the desired wave plate is in the polarimeter. The quick way to do this is to check which plate is in the box in the control room; the other one is therefore in the polarimeter. For linear polarimetry use the /2 plate, for circular (or simultaneous linear and circular) polarimetry the /4 plate. Only NOT staff should change the wave plate.

Check that the high voltage power supplies have been set to zero voltage, and if not, set them to zero. Also make sure that they are switched off. Switch on the CAMAC crate in the control room with the power switch at bottom left of the unit. Switch on the high voltage power supplies. Turn the voltage selection knobs to the correct settings. The UBV supply should have the voltage -1150 V and the RI supply -1800 V. These positions are marked on the front panels of the power supplies. Do not to put too high a voltage on the tubes, as this will cause permanent damage!

On the PC called TAMAR type d: and cd observer. Make a sub--directory for yourself by typing md name, if not already done. Go to your sub--directory by typing cd name. Then start the polarimeter control programme by typing pp. If the mouse does not work, exit from the PP programme, type pp mouse, and pp again. You should now have a running control programme.

Click the left mouse button on the FILE pull down menu to open the data file for the coming night. Give a filename including the date pyymmdd.dat is preferred.
On startup of the PP programme, some default parameters are set: linear polarimetry, integration time 10s, number of cycles 4. These values are normally used for stellar observations and one complete cycle takes about 15 minutes. For details about the various observing modes see the section on Observing below.

You are now ready to set--up the polarimeter on an object.