Environmental Control

Blanco 4-m Daily Procedures - Environmental Control

  • The mirror cooling should NOT be turned off for instrument change except for safety reasons. That is, if the noise or temperature is such that you are likely to make a mistake. If ever you do turn it off, DON'T FORGET to turn it back on!
  • The temperature control system automatically controls mirror temperature according to the following logic:
    1. Tmirror < Tgoal - 2.5°: glycol valve closed (but ambient air is still blown onto the mirror)
    2. Tgoal + 1.7° < Tmirror < Tgoal -2.5°: glycol valve partially opened
    3. Tmirror > Tgoal + 1.7°: glycol valve fully opened
    4. If Tmirror < Tdew_point + 7°: the glycol valve will close (safe limit to prevent condensation)
  • The cooling of the C floor and M floor in the dome is always ON. It is currently regulated automatically
  • The large stirring fan on the M floor (inside the dome) should always be ON when the dome is closed and OFF when the dome is opened. This fan improves greatly the air circulation inside the dome. It can be turned off during instrument change or any other works around the telescope if the noise bothers you. But turn it back on when you are done!
  • Oil Cooling: The cooling of the oil circulating under the R.A. rear and front pads is activated automatically when the pumps are turned ON by Observer support at sunset. The oil glycol valve is controlled (range is 1-2.25 V) by an equation involving the low dome and oil glycol temperature sensors. It is important that the oil cooling be working: if it is not, you can diagnostic it in Blanco ECS and OIL COOLING SCHEMA (the "before pad" and "glycol" entries on the OIL line will quickly indicate around 30°).
  • The Chimney Fans are located inside the chimney at the level of the primary mirror and suck ambient air into the mirror cell so as to form a laminar downward flow in the chimney. This is to prevent Cass cage heat sources from creating convection in the light path in the chimney. At all Cassegrain foci (f/8), Observer Support is to turn ON the chimney fans before sunset. The switch is on the power supply on the old console room desk. The night assistant must turn it OFF at the end of the night.Not in use at the moment..TBD
  • Air conditioning - Always leave on. Do not use heat sources at level M, MZ and C. Always keep passageway doors closed, especially the glass oor in front of the lift at GR floor, the cryocooler compressor and pump rooms). In general, respect the signs in the building.