For twilight proposals the Cadence Optimization White Paper Call has said there’s about 20-30 minutes per twilight available.
Doing some math for Cerro Pachón for current sunset/sunrise times: The time between nautical twilight is 11.58 hours. The time been 18 degree astronomical twilight is 10.6 hours. That leaves 0.98 hours between the 12 and 18 degree mark, divide that in two it’s about 20-30 minutes in the morning and evening twilight between 12 and 18 degree twilight. This matches the rough estimate in the document.
Should we assume that a twilight survey would start no earlier than 12 degree twilight and end at 18 degree twilight? In the current operations simulator when do observations start (does it vary by filter?)? Is there expected to be time taken by twilight flats or early observing in Y filter?
Does Project recommend that we focus on what can be done between 12 and 18 degree twilight and make a brief comment if we could use more twilight time later for the proposed twilight observing strategy if it is deemed safe?