Background

Removal of the DEIMOS tent mirror is a highly delicate operation which should ONLY be performed by a trained instrument technician. This procedure documents the steps followed during removal of the tent mirror in March 2005, led by Jeff Lewis and Matt Thompson of UCO/Lick Observatory.

Requirements

Procedure

  1. Attach extension transfer line to the DEIMOS fill port, allowing LN fills to take place while DEIMOS in secured in the required access position, which puts the LN fill port straight up.
  2. Rotate DEIMOS to the appropriate position for access to the interior (ROTATVAL=-270). At this poition, the tent mirror faces up and the personnel access hatch is situated on the left side of the instrument (as viewed from behind the collimator).
  3. Set the band brake and tag out the brake to prevent any instrument rotation during the time the mirror is out. NOTE: The brake should NOT be released until the tent mirror is fully re-installed and aligned!
  4. Acquire images to establish the position of the optics prior to removal. Refer to Optical Alignment Exposures.
  5. Using a slotted screwdriver, remove the personnel access hatch.
  6. Carefully enter the DEIMOS barrel. Be careful NOT to put weight onto the other access hatch, which is directly under you as you enter.
  7. Remove the downward-facing dummy tent mirror:
    1. Carefully detach spring arm at the thick edge of the wedge from the piezo mechanism.
    2. Have the assistant support the dummy mirror from below, taking care not to touch the witness samples attached to the surface of the dummy.
    3. Remove the two 10/32 screws from one of the side spring clamps.
    4. Remove the two 10/32 screws from the other side spring clamp.
    5. Gently lower the dummy tent mirror off of its mount.
    6. Remove the dummy tent mirror from the instrument.
    7. Re-install spring clamps and secure screws against loss.
    8. Use a cable tie to attach a foam piece to the piezo spring arm.
  8. Remove the upward-facing tent mirror:
    1. Have the assistant apply extremely gentle upward presure to the thin edge of the wedge-shaped optic. This will prevent the optic from rotating when the piezo actuator is detached.
    2. Carefully detach spring tensioner from the glued-on block on the thick edge of the tent mirror.
    3. Remove the two 10/32 screws from one of the side spring clamps.
    4. Remove the two 10/32 screws from the other side spring clamp.
    5. Applying gentle pressure from the backside, carefully lift the tent mirror vertically until it is clear of the mounts and the piezo registration ball/cone.
    6. Insert the tent mirror into the tranfer case, thick end first, reflective side facing up. Secure the plexiglass cover on the case.
    7. Re-install spring clamps and secure screws against loss.
    8. Use a cable tie to secure piezo actuator to the piezo mount block.
    9. Carefully pass the tranfer case out through the access hatch. Note that you must tilt the case to pass it through the hatch; ensure that the thick end is DOWN.
  9. Cover the tent mirror mount points with tape and tissue to prevent grit from accumulating there while the optics are removed.
  10. Exit instrument and secure access hatch.
  11. Ensure that instrument band brake is set and tagged out to prevent rotation.

See Also