Appendix C

Primary mirror cleaning The Primary mirror should be cleaned weekly by the primary observer or mountain support. The TCS computer air filter should also be cleaned when the primary mirror is cleaned. The seconday mirror Should NOT be cleaned.

To clean the primary mirror:

Frozen CO2 is used to clean the primary mirror and safety equipment must be worn at all times. Proper ventalation (open door) must also be maintained when using CO2.

  1. Start the TCS computer.
  2. Press the F9 key on the TCS computer keyboard to disengage the telescope drives.
  3. Reset both red telescope crash buttons.
  4. Disconnect all items from the telescope (LN2 Tank) and move all items on the observatory floor to their proper stored locations. The dome should be closed while cleaning and the outside door opened.
  5. Reset the Telescope Drive Interlock (see Appendix J, Figure A, Item #13) by pressing the button located on the box.
  6. From the TCS computer open the primary mirror covers.
  7. Using the hand paddle controller, move the telescope until it is pointing approximately +70 (-70, S. Hem.) degrees declination.
  8. Move the CO2 tank to the observatory floor and attach the cleaning apparatus to the tank. Connect the grounding wire to a secure ground on the telescope frame.
  9. Put on all safety clothing for handling CO2.
  10. Using the tall step ladder, move it to the telescope so that you have access to the the primary mirror.
  11. Turn on the CO2 and climb the ladder with the cleaning apparatus. Procede to clean the mirror using the following procedure.

    1. Do not get the end of the cleaning hose closer than 12 inches (30cm) from the surface of the mirror.
    2. Use a continuous motion when cleaning the mirror, do not allow the flow of CO2 to remain on one point on the mirror for longer than a second or two.
    3. Do not allow the CO2 spray to directly enter the hole in the center of the primary mirror.
    4. Use a sweeping motion from the top towards the bottom starting from the 12 O'clock position and working to the 3 O'clock position, then go back to the 12 O'clock position and work to the 9 O'clock position. Sweeping from the edge to the hole in the center and also downwards.
    5. Continue from the 9 O'clock position towards the bottom (6 O'clock) postion sweeping from the center outwards and downwards.
    6. Move to the 3 O'clock position and work towards the bottom (6 O'clock) postion sweeping from the center outwards and downwards.
    7. Repeat if necessary

  12. When finished, climb down from ladder and turn off the CO2.
  13. Move the ladder back to its storage place on the floor.
  14. Disconnect CO2 grounding wire and remove the cleaning apparatus from the tank.
  15. Move the tank back to its storage location.
  16. Close the mirror covers using the TCS computer.
  17. Issue a stow telescope on the TCS computer, to move the telescope back to its stow position.
  18. When telescope stops moving (at stow position), turn off the drives using the red crash buttons.
  19. Shutdown the TCS computer and turn it off.

To clean the TCS computer air filter:

  1. Open the door on the TCS computer to gain access to the filter holder.
  2. Remove the filter holder located on the left side of the computer.
  3. Remove the filter from the holder.
  4. Take the filter outside to clean by hand. Hold the filter in one hand and wave in the air to remove the dust.
  5. Put the filter back in the holder and insert back into the computer.
  6. Close the door on the TCS computer.

Appendix C

Version 2.3 - October 4, 1998