Twilight Sky Flats

Automatic Twilight Exposures

• The telescope should be tracking with the dome set to follow it (full-up observing mode).
• Start about 10-15 minutes before the sun touches the horizon.
• Type this in your MOP window:

  mt> autoTwilight -informGUI

  This starts a taking u band twilight exposures and continues until a good set is obtained. See "autoTwilight -help" for more information.

Manual Twilight Exposures

• Twilight flats in u-band can first be obtained in a one second exposure when the sun just touches the horizon.
• Verify that the telescope is tracking and the dome is engaged.
• Type this to point the telescope at the optimal twilight flat location:

  mt> pointToTwilight

• Click the "twilight flat" button (far left in the middle of the window). Check the desired filter, type an exposure time, and hit return.

Cloudy?

Cloudy weather sky flats are suspect and always less desirable than blue-sky flats. If the conditions suggest that these are the only kind you'll get, please make a note in the log.

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