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
- Tools
- Slotted screwdriver
- 5/32 Allen wrench
- Materials
- Tent mirror transfer case
- Two pieces of foam
- Two cable ties
- Tape/foam/etc. for covering tent mirror mount points
after removal
- Personnel
- One trained summit technician
- One assistant to support the mirror during removal
- Drawings
Procedure
- 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.
- 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).
- 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!
- Acquire images to establish the position of the optics
prior to removal. Refer to Optical Alignment
Exposures.
- Using a slotted screwdriver, remove the personnel access
hatch.
- Carefully enter the DEIMOS barrel. Be careful NOT to put
weight onto the other access hatch, which is directly under
you as you enter.
- Remove the downward-facing dummy tent mirror:
- Carefully detach spring arm at the thick edge of the
wedge from the piezo mechanism.
- Have the assistant support the dummy mirror from
below, taking care not to touch the witness samples
attached to the surface of the dummy.
- Remove the two 10/32 screws from one of the side
spring clamps.
- Remove the two 10/32 screws from the other side
spring clamp.
- Gently lower the dummy tent mirror off of its mount.
- Remove the dummy tent mirror from the instrument.
- Re-install spring clamps and secure screws against
loss.
- Use a cable tie to attach a foam piece to the piezo
spring arm.
- Remove the upward-facing tent mirror:
- 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.
- Carefully detach spring tensioner from the glued-on block on
the thick edge of the tent mirror.
- Remove the two 10/32 screws from one of the side
spring clamps.
- Remove the two 10/32 screws from the other side
spring clamp.
- 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.
- Insert the tent mirror into the tranfer case, thick
end first, reflective side facing up. Secure the
plexiglass cover on the case.
- Re-install spring clamps and secure screws against
loss.
- Use a cable tie to secure piezo actuator to the piezo
mount block.
- 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.
- Cover the tent mirror mount points with tape and tissue
to prevent grit from accumulating there while the optics are
removed.
- Exit instrument and secure access hatch.
- Ensure that instrument band brake is set and tagged out
to prevent rotation.
See Also