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Дата изменения: Sat May 29 02:17:49 1999
Дата индексирования: Sat Apr 9 23:01:15 2016
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2.5m Telescope Procedure

Procedure for Opening, Closing, and Moving

the SDSS 2.5-meter Telescope

Prepared by D. Long, W. Boroski, and A. Prosapio

Maintained by: Mark Klaene

Revised 3/29/99

 SCOPE

This document contains procedures for opening and closing the SDSS 2.5m telescope enclosure, and for preparing to move the telescope. Only those persons that have a need and have been trained by the observatory staff may operate the enclosure and telescope. Once trained your name will be posted by the telescope status board.
 

OPENING THE TELESCOPE ENCLOSURE

  1. Check the whiteboards in the Ops building and the 2 levels in the telescope enclosure for the current status of the telescope and any other notes that may pertain to opening the enclosure. Indicate your planned change of status.
  2. If the sun will be more than about 15 degrees above the horizon at any time while the telescope is open, place the cover over the end of the wind baffle assembly. Installing the cover is a two-person operation.  A nearby stop button (which is in sight) must be in and the telescope altitude brake engaged and the telescope at the horizon while the cover is installed.
  3. Check that weather conditions permit opening.
    1. Daytime:
    2. If closed, may open at:
    3. Sustained wind speed < <40 MPH for 15min;
    4. Wind gusts for instrument changes< <30 MPH
    5. Dew point depression >= 6 Deg F
    6. Dust count < <10000
    7. NO threat of precipitation (remember that it takes nearly 20 minutes to close up).
  4. If open, close at:
  5. Sustained wind speed < >40 MPH for 15min;
  6. Wind gusts for instrument changes< <30 MPH
  7. Dew point depression <= 4 Deg F
  8. Dust count < >10000

  • Nighttime:
  • If closed, may open at:
  • Sustained wind speed < <435MPH for 15min;
  • Wind gusts for instrument changes< <30 MPH
  • Dew point depression >= 6 Deg F
  • Dust count < <2500
  • NO threat of precipitation (remember that it takes nearly 20 minutes to close up).
  • If open, close at:
  • Sustained wind speed < >35 MPH for 15min;
  • Wind gusts for instrument changes< <30 MPH
  • Dew point depression <= 4 Deg F
  • Dust count < >3000

  • Checks for condensation should be made regularly when the depression is less than 8 Deg F. Close if condensation is found on the rails, building skin , or top of the doghouse.
  • Do not push the dust limit and the dewpoint limit at the same time. If the counts ar over 3000, it would be best to have a depression of > 20 Deg F.
  • Make sure nothing obstructs building motion. Inside the building, make a check of the floor to the south of the dashed warning tape and clear everything out of that area, including the phone.
  • Close the enclosure hatch doors. (NOTE: The interlocks for the hatch doors may be bypassed, so the building will move with the hatch doors open.)
  • Check the building rails (inside and out) for possible obstructions.
  • Verify that the telescope is in the stow position. For the altitude axis, the windbaffle dashpot will be in contact with the windbaffle frame.  For the azimuth axis, the green azimuth stow indicator light will be lit.  As an extra measure, visually check that the telescope is centered in the overhead door opening.
  • Push in at least one stop button (which is in sight) to make sure that the telescope drives remain disabled.
  • Verify that the telescope axes brakes are applied. The telescope and wind baffle must be reasonably balanced as well.
  • Secure any lightweight objects likely to blow around once the enclosure doors are open.
  • Open the enclosure overhead doors.  Open the east door first if the winds are from the west, otherwise, open the west door first. The red flashing light in the NW corner of the building will turn off when the west door is fully open. 
  • As the west door is being opened, verify that the west overhead door is free of snow, ice, or other debris that might fall on the telescope when the enclosure is moved.
  • The west door must be fully open before moving the enclosure. Verify this by making sure that both sides of the overhead door are above the red marks on the west door frame.   Although the east door needn't be fully open to move the enclosure, it must be sufficiently open to provide the building operator with a clear view of the area over which the building will move.  It is highly recommended that the door be fully open during operation due to wind loading considerations.
  • Remove the building pins at the NW and SW corners. With both pins removed, the yellow flashing light in the NW corner of the building should be off.

    • ***NOTE***   The intent of the yellow flashing light is to provide an indication that both pins are properly installed when the building is stowed.   Therefore, the logic of the yellow flashing light causes it to flash only when both pins are in.   Removing either pin will cause the light to go out. Physically verify that both pins have been removed before attempting to move the building. Do not rely on the state of the light).

  • With the control set to slow, move the enclosure east until the west door is clear of the telescope.  At this point, the enclosure speed can be increased to the fast mode to move the enclosure the rest of the way to the Building Clear position.  Note that in fast mode the enclosure coasts one to two feet when stopping, so when approaching the end of travel, switch back to slow speed.  In slow speed, the enclosure will still coast 6 to 8 inches so let up on the control at least that far away from the stops to avoid running the enclosure into the stop.  At the east end of travel, the enclosure will contact the building clear switch. Avoid having the building impact the stops under power or at a high speed.

    • MOVING THE 2.5-METER TELESCOPE

    1. Verify that the enclosure is fully away from the telescope.  There is an interlock that prevents telescope motion unless the enclosure is in the Building Clear position.  However, if this interlock is bypassed, it is the responsibility of the operator to ensure that the enclosure is fully clear of the telescope.
    2. Verify that the telescope is not grossly out of balance.
      1. The telescope is balanced top/bottom by the counterweights. This is done with the altitude axis near the horizon.
      2. the telescope is also balance for and aft. This is done with the altitude axis near Zenith. Currently this is done by adding or subtracting weight on the back of the telescope PSS. This can only be done by certified persons.
      3. Verify that the counterweights are properly positioned for the current instrument configuration.  Counterweight positions for the various instrument configurations can be found in the Counterweight Position Table.
      4. Verify that either the spectrographs or the dummy spectrograph weights are installed.
      5. One may also use the following procedure to check the balance:
        1. Press in a stop button (which is in sight) to disable the telescope drives.
        2. Release the altitude brake and observing whether the telescope moves in altitude within the windbaffle.  If balanced, the telescope should not move or should move very slowly.  If the telescope begins to move rapidly, then the telescope is not properly balanced.  Quickly re-apply the altitude brake, rebalance the telescope, and repeat this step..
        3. Once this test is complete and balance verified, re-assert the altitude brake and release the stop button.
    3. Inspect the drive surfaces for contaminants such as dirt or moth guts. If any work has been done around the telescope, inspect the drives for metal shavings. Clean up any such debris and wipe down each drive following APO cleaning procedures. You must have a stop button pushed in (which is in sight) while cleaning the drives.
    4. Check the status of the interlock system by looking at the front of the receiver/splitter chassis in the Telescope Controls System relay rack.  Understand the nature of any tripped or bypassed interlocks before attempting to move the telescope.  Failure to do so may result in serious damage to the telescope.
    5. Make sure the lower enclosure is clear of any objects in the path of the rotating racks.
    6. Verify that the altitude locking pin is not inserted.
      7. The altitude pin is interlocked. One could do serious damage moving the telescope manually with the windbaffle, if the pin is left inserted.

    7. Release all stop buttons except the one on the north side of the windbaffle frame.  This button is nearest the MCP laptop.
    8. Turn on the telescope drive amplifiers in the lower enclosure.  Verify that the normal set of LEDs is lit on each of the amplifier front panels.
    9. Verify that the windbaffle axis control system is configured to run in servo mode. The alt/az cables should be connected to their respective connectors inside the windbaffle control panel.  The manual pendant should not be connected.  
    10. Power up the windbaffle servo system.
    11. Log into the MCP and start the Menu program (telnet to sdssmcp, then type Menu). Instructions for using the Menu program can be found at http://tdpc 01.fnal.gov/sdss/docs/tech_notes/MCP_menu_doc.html . Note that only one connection is allowed into the MCP at a time, so be sure it isn't already being run somewhere else before you start.
    12. Using the Menu program, release the telescope azimuth brake.
    13. Using the Menu program, operate the telescope-to-windbaffle alignment clamp to center the telescope within the windbaffle. Once the telescope has been centered, release the clamp.
    14. Release the final stop button.
    15. Reset the amplifiers to clear the internal inhibits.  The windbaffle should center up on the telescope at this point. 
    16. From the Menu program, select altitude controls (l), then press (h) to hold the telescope in the current position.
    17. Using the Menu program, release the telescope altitude brake.  If the telescope is properly balanced, the telescope should not move when the brake is released.
    18. The telescope can now be moved using the Menu program. The interlock system will prevent azimuth motion until the telescope altitude elevation is greater than 15 degrees. The15-degree stop will automatically engage when the telescope reaches approximately 18.5 degrees.

    CLOSING THE TELESCOPE ENCLOSURE

    1. Check that nothing will interfere with moving the telescope to the stow position.
    2. Move the telescope to stow position in azimuth first. Be sure that the doghouse won't run into anything as it swings around. Also be sure that the altitude is high enough not to hit anything as it moves in azimuth. The azimuth Stow Position Indicator light will turn on when the telescope is properly positioned.
    3. Verify that all enclosures on the front of the PSS are latched. For example, the latch control box lid will catch on the floor if it is not closed when the telescope comes to stow in altitude.
    4. With the telescope in the azimuth stow position, slowly bring the altitude down to 0.9 degrees.  Make sure there is nothing in front of the telescope when it comes down. The 15-degree stop will automatically disengage when the telescope reaches approximately 17.6 degrees.  With the telescope at 0.9 degrees, verify that the windbaffle frame is in light contact with the lower dash pot.
    5. Apply both the altitude and azimuth axis brakes.
    6. Turn off the drive amplifiers and the windbaffle servo system.
    7. Push in at least one stop button on the upper level near the telescope.  Stop buttons usually engaged when telescope is at stow include the one in the lower enclosure next to the breaker panel on the east wall, the one on the north windbaffle frame, and the one in the 2.5m control room.
    8. Make sure the way is clear for building motion (hatches closed, dewars and phone clear, etc.).
    9. Make sure the west door is fully open.  Both ends of the door must be above the red marks on the door frame.  Also, the red flashing light in the NW corner of the building will be off when the door is fully open.
    10. Move the building west toward the telescope. You may start out fast, but you must change to slow speed just before you move over the telescope. This will provide a much shorter coasting distance (6-8 inches) should you need to stop quickly. You may go back to fast after the west door clears the back of the telescope, but be aware of the coasting distance as you come up to the building stops.
    11. With the enclosure against the west stops, insert both building pins.
    12. Close the enclosure overhead doors.  If the wind is from the west, close the west door first.  If the wind is from the east, close the east door first. 
    13. Verify that at least one stop button is pushed in near the telescope.
    14. Update the status of the telescope on the whiteboard in the Ops building near the door to the 3.5m telescope arcade.


    Updated 03/29/99