Closing down Telescope and Dome

1. Before moving the telescope to the park position, switch off the Cassegrain (if in use) and Finder TV cameras, and switch off the Autoguider. It is important that this is done before slewing the telescope, in order to avoid accidental damage to the cameras by a possible bright object appearing in the camera field. The TV cameras are controlled from small racks near the top of right-most panel of the Control Desk, to the left of the Autoguider Control. Switch the cameras off by turning the gain controls anti-clockwise until they click, followed by pressing the small red OFF button. The autoguider is switched off by pressing the ONOFF button on the rack to the right.
2. Move the telescope to zenith by pressing ZP on the Control Desk (Bay 2, Rack 3). This also disables the dome tracking.
3. Close the PRIMARY and SECONDARY mirror covers IN THAT ORDER by operating the MIRROR COVER CLOSE on the Engineering Rack. This must be done before closing the dome shutters for safety reasons.
4. Switch to Engineering mode by pressing the ENGCOMP on the Telescope Control Desk.
5. Close the dome shutter(s) by pressing LOWERMICRO button on the Engineering Rack until the MAIN OVER TRAVEL light is out, followed by pressing the LOWERMAIN button until that light comes on again, and then finishing with pressing anew LOWERMICRO for about 10 seconds. This procedure has to be done for BOTH shutters, starting with the Lower Shutter (buttons on the right), but only if that shutter happens to be raised, which will not often be the case. The control buttons for the Upper Shutter are found on the left-hand side of the Rack.

   The main (upper) shutter should be at a zenith distance of 71.9 degrees when fully closed. This value is listed on the Information Display (section ) as `Upper Shutter ZD'. Take care: if only ``*''s are displayed, this normally means that the Dome is fully open. Thus, a visual inspection is the best way to ensure that the Dome is properly closed. Note, that the MAIN OVER TRAVEL indicator light for the Upper Shutter will be on when the dome is closed; this is a necessary condition, but not a sufficient one.

6. Switch off the dome fans and (if necessary, it is rarely done) replace fan covers.
7. Switch off the EXTRACTOR and INPUT ventilators, on the second and the ground floor, respectively, by pressing the red stop button on the control panel near the telescope base, which can be reached via the small Coude room opposite the CLIP Centre (beware oil on the floor!).
8. Close the Finder Cover.
9. When working at Cassegrain, the Primary Mirror Plug will have to be replaced; when in Prime Focus Mode, the telescope has to be parked in the Access Park position. In both cases, move the telescope to the park position (manually; the PARK ACCESS button does not work!) by following the procedure described in item 12 of the previous section :
   1. Move the telescope to the North Horizon Limit; use an Hour Angle of exactly 24.00 hours, so that the telescope needs to be moved in Declination only. If the Hour Angle is not exactly 24 hours, the telescope will hit the platform.
   2. Press the Declination QM (Quick Motion) button on the Engineering Rack until the green light comes on to signal that the mode is engaged. The corresponding light of the SM (Slow Motion) button must be off.
   3. Press the Declination + button, which actually moves the telescope, until the alarm sounds as sign that the telescope has run into a limit. Now press the Accept button on the Control Desk to switch the alarm off.
   4. Turn the key-operated LIMIT switch on the Engineering Rack to the O/R position (limit override).
   5. Repeat steps b) and c). This time there will be no alarm, but the telescope will halt in Park Access position when it runs into a second limit switch.

      In Prime Focus mode, leave the telescope in this position. In Cassegrain mode, replace the mirror plug, and move the telescope via the pole position back to zenith, as follows:

   6. Press the Declination - button to move the Telescope back to the the pole position at declination 90.
   7. Turn the LIMIT switch to the NULL position.
   8. Press the SM button on the Engineering Rack.
   9. Switch to computer mode by turning the key on the Control Desk.
   10. Press the ZP button on the Control Desk to move the telescope to the `zenith park' position.
10. Press the EMERGENCYSTOP button in order to disable any subsequent motion of the telescope. This is not essential, but good practice. One has to remember, however, to press the RESET button before starting up in the following afternoon.
11. Switch off the oil pump, by pressing the OIL PUMP switch on the Engineering Rack.
12. But DO NOT SWITCH OFF POWER to either Dome or Telescope.
13. Top up the Cryostats with Liquid Nitrogen.
14. Check that the access doors to the dome are closed.