Recommended Procedures for the Wind Blinds

The observers are expected to pay attention to the wind speed, since wind can shake the telescope, especially with the dome pointed into the wind. On Tololo the wind is typically out of the North. Alistair demands:
  • When wind speeds are >5-8 mph (8-13 kmh), ask the TelOp to raise the wind blind (closes the lower part of the dome slit).
  • When wind speeds are >15 mph (24 kmh), ask the TelOp to close the louver windows around the dome floor.
    At low wind speeds, it's best to keep everything open to maximize ventilation of the dome.

Any change in the configuration of the wind screens should be put in the DECam Logbook.
Please use words "wind screen" in the text and tag the entry as "Summary".

Note on potential vignetting due to the windscreen

As the "windscreen" is just the cover of the lower half of the dome slit, there is the possibility that "vignetting"--blocking of the telescope beam by the windscreen--can occur when pointing at fields at high airmass=low altitude=high zenith distance=close to the horizon. During normal survey operations, obstac typically sticks to fields at airmass < 1.4, where there is no risk of occlusion by the windscreen. Below is a screenshot of the prime focus camera (looking outwards) taken when the windscreen was raised and we were pointing at a standard star field at airmass 1.55 = 40 degrees off the horizon.

The two vertical lines are the two sides of the dome slits, and the lower horizontal line is the top of the windscreen. If you're going to point much lower on the horizon than this (e.g. during high-airmass standards), you might want to ask TelOps to lower the windscreen for you, or at least keep a close eye on the prime focus webcam.