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Turpol setup procedures

Table Of Contents:

Staff setup Procedure - Preparing TurPol


Cooling of the instrument takes at least 4 hours and it should therefore be mounted a reasonable time ahead of this.

Mounting Turpol on the telescope

TurPol must be mounted on the adaptor in such an orientation that the ocular tube is pointing 180 degrees AWAY from the StanCam dewar. (Follow the marks.) Otherwise the periscope optics for viewing the diaphragms on TV do not work properly. The correct mounting bolts are listed inside the telescope fork. (Use the green ones without washers.) Make sure that the tubes leading to the refrigerator unit are free to move with the telescope movement and do not snag on anything.

Remember to balance the telescope correctly. Set the counter weights to position 0.12 by typing on the TCS count-w-hei 0.12. You can check how well the telscope is balanced at alt 60 (zenith angle 30) and with open mirror covers o-m-c, and then look at TCS status page 3, where the currents to the two altitude motors are displayed. These currents (Altitude Motor 1 and 2) should have approximately equal absolute values. Then type zenith to put the telescope back.

The default telescope focus is set with the command foc-pos 24350. The default guide TV focus is set typing tv-foc 650.

Cooling system

Check that the cooling system is operating, and that the indicated temperature is between -16 and -20 degrees Celsius. 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''. In case of malfunctioning, refilling of freon might be needed. Contact the cooling expert (Carlos Perez) for instructions, or if not possible, follow the TurPol Cooler Manual .

Instrument setup

  1. Wave Plate

    Normally TurPol is equipped with the /2 retarder, which provides measurements of linear polarisation only. In order to measure circular & linear polarisation simultaneously, or to do circular polarimetry, the /2 plate must be replaced by the /4 plate.

    To do this, you have to remove the 4 small bolts (3mm Allen key) from the upper part of the back cover of the polarimeter, disconnect the motor cable and carefully slide out the module in which the wave plate is mounted. Note that to be able to slide the module out, you have to also remove two of the big instrument mounting bolts on that side. Take the module into the control room or electronics room to be able to work on it at a table.

    Unscrew and remove the /2 plate from its holder and put the /4 plate instead (or vice-versa, of course). The orientation of the /4 wave plate optical axis must be such that in the starting position, defined by just actuating the microswitch, the optical axis marked with the golden lines in the cylindrical wave plate mounting must be at 45 degrees to the sides of the rectangular black aluminium plate supporting the unit. This is most easily done by rotating the large gear clockwise from this starting position by an amount corresponding to two full rotations of the small gear (which has a fiducial mark to be able to do this). In this position, the wave plate mark should be placed parallel to the sides of the unit, or ``vertical'' when you hold the module with the small gear downwards.

    The orientation of the /2 plate should also be parallel to the sides as above, but with the big gear in the starting position defined by the microswitch. The surface of the wave plate mount with the optical axis mark should look upwards, i.e. be visible from the side of the big gear.

    Changing the wave plate should be done by NOT staff only.

  2. Selecting Polarimetry or Photometry

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

  3. Shutter

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

  4. Power

    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!

CAMAC Crate and tests


  1. Crate controller K-16

    Dataway display
    Timer TMP-Module
    Polarimeter Interface Module
    Counter #2
    Counter #1

    1 U, 3 V, 2 B, 4 R, (5 I)

    N1, N2, NP, NTPM, NDD, NCC

    Terminal, To IBM/PC

    NCC = MAX. position
    NDD - ANY position
    NP - ANY position
    NTPM = NP + 2
    N2 = NP - 2
    N1 = N2 - 1

    For Observation Mode:

  1. Install the jumpers inside the NP module in position "1".
  2. Run PP.EXE from personal directory.

    For Self Testing Mode:

  1. Disconnect the 38-pin ELCO from polarimeter.
  2. Reinstall both jumpers inside the NP module in position "2".
  3. Disconnect and short "OUT 5" from NP module.
  4. Run PP_ DEMO.EXE.

Note! (For all computer men): PC-CAMAC adapter card use I/O ports 0x340 hex - 0x34F hex and IRQ 9, don't conflict!

Back to top Last modified: 19-Apr-2010