Maryland-Magellan tunable filter installation orientation

Fastening the etalon to its mounting plate

The MMTF is optically symmetric and not sensitive to orientation, but it needs to be installed on its plate with the cable ports pointed in the correct direction and a particular side up, or the cables may not reach or may bind when the etalon is clamped into observing position.

MMTF on mounting plate. Note the lettering on the cable ports is upside-down with the plate under the etalon.

View from above. Note the location of the cable ports relative to the ears of the mounting plate.

The MMTF installed in the IMACS disperser wheel, at the service position. There is only one possible orientation of the mounting plate to the IMACS disperser wheel. Note orientation of cables - if the etalon is correctly on the plate, it should match. When the etalon is clamped into observing position, it moves to the left. The medium-size etalon cable, leftmost in this picture, clears the hole in the disperser ring, but the large etalon cable (rightmost) would not. This is why it matters which "side" of the MMTF is up on the mount plate.

Benjamin Weiner, bjw at as.arizona.edu, 15 Nov 2006