Go Terps!
The Maryland-Magellan Tunable Filter
printable version
  1. Note: The etalon weight is 19.5 kg, not including the mounting plate.
  2. If the MMTF etalon is not attached to its mounting plate, attach it. The orientation of the etalon is important. In the left figure below, the CS-100 cable ports are in the correct rotational orientation (at the bottom of the picture) with respect to the mounting plate flanges. In the right figure below, the ports are such that the etalon is right-side up.

    A top view of the MMTF, attached to its mounting plate. Note the correct orientation of the CS-100 cable ports (at bottom) with respect to the mounting flanges. (Click for a larger image.)

    A side view of the MMTF, attached to its mounting plate. Note the correct orientation of the CS-100 cable ports, ensuring that the etalon is right-side up. (Click for a larger image.)

  3. Ensure that the two clear, protective covers covering the etalon aperture are in place.
  4. Secure the etalon in the disperser wheel using the same procedure as for other IMACS gratings. In the disperser wheel service position, the MMTF cable sockets will be pointing out and down, as shown in the image below (in the "5 o'clock" position as viewed from the rear of the instrument, looking toward the telescope).

    A view of the MMTF when mounted in the disperser wheel, with CS-100 cables connected. (Click for a larger image.)

  5. Plug into the MMTF the 5 cables connecting the etalon to the CS-100 controller. Be sure that the X, Y, and Z cables are matched properly with their respective sockets.
  6. Remove the two covers protecting either side of the etalon aperture.
Filters and Masks

1. Install the intermediate-band blocking filters specified by the observer.

2. Install MMTF slit mask ID #2049. This mask will be used for checking the position of the optical axis.

3. If charge-shuffling has been specified by the observer, insert MMTF slit mask "A".

Etalon CS-100 Controller

WARNING: Never set the Zcoarse dial on the CS-100 below -2! Doing so may damage the etalon coating.

CAUTION: The cables between the CS-100 controller and etalon should never be attached or removed while the CS-100 power is on.

Front panel of the CS-100. (Click for a larger, more readable image.)

The CS-100 is the electronic brain of MMTF. It is located in the IMACS electronics rack. For a more detailed description than that provided here, read the CS-100 manual.


Initial Configuration

  1. Ensure that the Mode knob is in the Balance setting. Power on the CS-100.
  2. Ensure that the CS-100 Meter Display knob is set to Offset. Using the knobs on the left side of the CS-100, dial in the following numbers to balance the capacitance feedback loop and parallelize the etalon. Replace ? with the Zcoarse specified by the observer.
        coarse fine  quad
    X   -1     7.11  4.20
    Y    0     6.80  3.78
    Z    ?     4.10  4.34
  3. Turn the Mode knob to Operate. After a few seconds, the Operate light should illuminate, indicating the feedback loop is now in active operation and functioning properly. If instead the Out of Range light illuminates, the etalon must be re-balanced; follow the balancing instructions.

Changing Zcoarse

Follow this procedure.