Background

Removal of the DEIMOS collimator 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 collimator mirror in July 2005, cmpleted by Vern Wallace, Jeff Lewis, and Jim Ward of UCO/Lick Observatory with assistance from Mike Wagner, Junichi Meguro, and Tim Saloga.

Phase 1: Prepare to Lift Collimator Cell from DEIMOS

Requirements

Procedure

  1. Position DEIMOS at the in-beam (NRT2) position in order to allow safe access to the rear of the instrument.
  2. In order to generate repeatable hysteresis on stages, first Rotate DEIMOS to its negative limit (ROTATVAL=-360) then to its positive limit (+270), and finally to the appropriate position for access to the interior (ROTATVAL=-180). At this position, the collimator removal hatch is up, and the DEIMOS barrel can be entered via personnel access hatch 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 collimator 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. To provide access to the collimator hatch, remove cladding panels number 5, 6, and 7 from the back of DEIMOS by using a slotted screwdriver to undo the 1/4 turn fasteners..
  6. Remove the two black metal brackets which supported the removed cladding panels using 7/16 combo wrench and socket.
  7. Use 5/32 Allen wrench to remove screws securing panel panel number 1. Also remove the two screws in the left adjoining panel to allow the foam pad to be removed. Remove panel 1 and foam, revealing the access hole for the counterweight support assembly.
  8. Using a slotted screwdriver, remove the personnel access hatch on the left-hand side of the DEIMOS barrel.
  9. Carefully enter the DEIMOS barrel. Be cautious of the tent mirror and the witness samples mounted to it.
  10. Apply tension to the counterweight support wire by tightening the nut on the wire. Begin by hand-turning the nut several turns clockwise until it becomes too hard to turn by hand. Then use a 1/2" open-ended box wrench to turn the nut several additional turns clockwise until it feels snug.
  11. Inside the instrument, remove the baffles covering the collimator mirror:
  12. Install the Lexan mirror cover:
  13. If the alignment jig [D2355] is installed on the mirror, remove it by using a slotted screwdriver to loosen the six 10-32 spring-loaded shoulder screws which secure the jig to the mirror. Note that the screws are kinematically located to return to the same place.
  14. While one person observes from above the mirror on the inside, have another person at the back of the instrument use the 1/2" box wrench to tighten the nut on the counterweight cable until the counterweight shaft (aka "lever") is horizontal. This will probably require turning the nut until the end of travel.
  15. Remove the collimator hatch cover at the back top of the DEIMOS barrel by unscrewing 24 bolts on the cover with 5/32 Allen wrench.
  16. Using a 3/16" Allen wrench, loosen and remove the bolt attaching the locking dog to the end of the counterweight shaft. NOTE: this is a very difficult operation. Best access is through the collimator access hatch on top of the instrument. If this is not practical, try accessing it by reaching over the collimator from the inside. Store these components for later use.
  17. Use slide hammer to remove the two taper pins that define the cell. For each pin:
  18. Install the center of the Lexan cover by hand tightening the 2 red captive thumbscrews.

Phase 2: Remove the Collimator Cell from DEIMOS

Requirements

Procedure

  1. Position pallet cart and pallet on dome floor at a point where the jib crane can lower the load onto the pallet. Top pallet with Ethafoam padding panels if available.
  2. From inside of the DEIMOS barrel, undefine the collimator mirror cell from the instrument by unscrewing 6 of the 8 bolts that attach the cell to the instrument using 5/16" Allen wrench and/or 5/16" hex bit straight-end socket plus 3/8" ratchet.
  3. Remove the collimator hatch cover on top of the instrument if not already done.
  4. Remove the center panel of the Lexan cover by unscrewing the two red thumbscrews. Otherwise, this panel will interfere with lifting cell.
  5. Back DEIMOS away from telescope to allow jib crane access:
  6. Rotate the dome to position the jib crane over the instrument.
  7. Remove the counterweight support shaft ("lever"):
  8. Insert two 1/2 inch shackles onto FRONT lifting holes in the top of the collimator mirror cell. NOTE: two pairs of holes exist. The FRONT set is for use when the mirror is installed in the cell. The REAR set is used when the mirror cell is empty.
  9. Attach a lifting strap (4' min, 6-8' ideal, 10' preferred) to each lifting shackle and onto crane hook. Note: with 10' strap you will only have 1" clearance when optic is fully lifted.
  10. Slowly raise hoist in "slow jog mode" until the lifting straps are tensioned. Crane operator should then adjust positioning of crane (in/out and left/right) to ensure that the hook is directly above the mirror cell. Do this by inspecting the angle of the cabling supporting the crane hook from two directions (behind DEIMOS and from the side).
  11. Position one person at the rear of the instrument and one on the inside to guide the mirror cell up and out. The person at the rear will be responsible for reaching into the counterweight access hole in panel 1 and pulling back (away from telescope) on the steel sleeve passing through the mirror center; otherwise, this sleeve will prevent the cell from moving.
  12. Continue raising mirror cell slowly until it is high enough to clear the back of the instrument.
  13. Affix heavy tag line (1/2-5/8" diam rope) to mirror cell in order to control motion. Have one person stand on Nasmyth deck and hold tag line during motion.
  14. Slowly rotate telescope dome to move the jib crane and load away from the Nasmyth platform. Continue moving until positioned directly over the pallet cart on dome floor.
  15. Send crane operator and one or more additional people to the dome floor in preparation for lowering the load.
  16. Slowly lower the mirror and cell to the dome floor. Adjust pallet position as needed so that the bottom edge of the pallet touches the front of the pallet. Rotate the cell so that the mirror will be up as the load is lowered. Continue lowering cell until it is fully supported on the pallet.
  17. Remove lifting straps from crane hook, and remove shackles from mirror cell.
  18. Slowly roll the pallet crate into the coatings lab for next phase.
  19. If NIRSPEC observing will take place before collimator is re-installed, Back DEIMOS onto Nasmyth deck (RT4), then move it into NRT1 position for storage.
  20. Re-install exterior cladding and insulation panels on DEIMOS to prevent dust intrusion.

Phase 3: Remove the Collimator Mirror from Cell

Requirements

Procedure

  1. Install adapter plate onto mirror cart per Tim Saloga.
  2. Attach 4 ?? (size) lifting bolts to the mirror cell (into what holes?).
  3. Attach 4 3' lifting straps to the hoist hook.
  4. Slowly lift the mirror cell about a foot off of the pallet.
  5. Roll away the pallet cart and pallet.
  6. Insert the lifting spider underneath the mirror cell. Rotate the spider so that the arms align with the radial pads on the cell.
  7. Slowly lower the cell onto the lifting spider, centering the cell to allow about 1/2" clearance between cell and pads on spider arms.
  8. Remove lifting straps and lifting bolts from cell.
  9. Remove the Lexan cover by undoing the red thumbscrews.
  10. Remove the aluminum cell side plates (one marked 180R, the other 180L) by unscrewing 14 flathead hex screws with 5/32 Allen wrench.
  11. Measure the depth of the mirror surface below the cell surface using a depth micrometer at three locations: NOTE: To make the measurements, place the micrometer base on the cell wall and lower the micrometer gauge until it contacts the ground flat on the mirror edge.
  12. Remove the top axial pad (labeled 180T) and spacers by using ?? (size) Allen wrench to loosen bolts on underside of the cell lip.
  13. Measure the gap between the mirror and the cell ring using a small hole gauge and micrometer. Measurements:
  14. Re-install Lexan cover using thumbscrews.
  15. Attach lifting straps and hooks to eye bolts on spider arms. Attach straps to hoist hook.
  16. Slowly raise cell about 2' using hoist.
  17. Insert the collimator mirror installation/removal tool ("milking stool") under the cell. Position the tool so that each leg is aligned with a spider arm, allowing the legs to insert into holes in the back of the cell.
  18. Slowly lower the cell onto the tool, ensuring that the legs enter the holes in the cell back. Stop when the legs just contact the back of the mirror. [??]
  19. Remove top left (soft) radial pad using Allen wrench to undo 4 spring-loaded bolts. Remove the pad and the cylindrical insert.
  20. Using the hoist, lower the lifting spider and cell to the floor; the mirror will remain standing on the tool legs.
  21. Remove shackles and lifting slings from lifting spider.
  22. Raise the hoist out of the way.
  23. Re-install the soft radial pad by positioning the pad in place (NOTE: 0° mark on pad points up) and inserting the 4 spring-loaded screws (if possible).
  24. Remove the retaining ring in the center of the mirror by using 5/32 Allen wrench to undo 6 hex-head bolts which attach on the back of the mirror.
  25. Install the stainless steel and neoprene lfting band around the circumference of the mirror. Position the two halves of the band so that they lie in the center of the mirror rim. Insert a rod piece into the loop in the sleeve. then insert a bolt through the rod and into the block on the end of the other band half. Use large Allen wrench to tighten the bolts to a reasonable torque. [??]
  26. Install 4 earthquake clips to the blocks on the lifting band in order to secure the mirror to the band. Position the body of the clip on the block so that the rubber pad is hard against the bottom of the mirror, then depress the spring plunger in the pin and insert into the clip body to secure the clip to the band.
  27. Install 2 ?? (size) lifting rings onto the lifting band blocks.
  28. Attach a 3' lifting strap to each of the two lifting rings.
  29. Move the hoist hook well away from the mirror.
  30. Install Tim's spreader bar on the hoist hook.
  31. Slew the hoist over the mirror and attach the lifting straps to to the ends of the spreader bar.
  32. Very slowly raise the hoist to put tension on the lifting straps. Carefully observe the position of the lifting straps on the mirror edge as you continue to raise the mirror and stop immediately of any slippage is noted; this would indicate that you need to lower the mirror and re-tighten the lifting band.
  33. Raise the hoist to lift the mirror off of the installation/removal tool legs.
  34. Wrestle the empty mirror cell, lifting spider, and installation/removal tool onto a pallet cart using several strong bodies. Remove these parts to another area for storage until reinsertion time.
  35. Insert the DEIMOS collimator coating fixture under the mirror. Ensure that the retaining pads are removed and the 8 neoprene pads are installed around the perimeter.
  36. Slowly lower the mirror onto the fixture, centering as you lower it.
  37. Detach the lifting straps and remove the lifting rings from the lifting band.
  38. Remove the band from the mirror by loosening the 2 large hex bolts which attach the two halves to each other.
  39. Install all 4 retaining pads onto the fixture, using doubled 1/4" neoprene padding at each pad to cushion the perimeter of the mirror.
  40. Install 3 lifting rings to threaded holes in the perimeter of the coating fixture.
  41. Attach 3 lifting straps from the 3 lifting rings to the hoist hook.
  42. Slowly raise the hoist and lift the mirror until it is sufficiently high to clear the mirror cart.
  43. Roll the mirror cart into position below the mirror fixture.
  44. Slowly lower the mirror fixture onto the cart.
  45. Use ?? (number, size, type) bolts to secure the fixture to the cart.

See Also