Programs are typically run in queue. It is important to to be aware of overheads when receiving your allocated time. The time allocated to each program is clock time and includes acquisition, calibrations, and other detector and telescope overheads.
Obtaining astronomical observations at any telescope will typically face four different sources of overhead: from the telescope, instrument, detector and any operation that requires human interaction. The Table below summarizes these overheads.
|Source of Overhead||Action Type||Typical Time [sec]||Maximum Time [sec]|
|Instrument||Camera, Pupil Alignment||60||300|
|Human Element||Field/Source Identification||5||300|
|Source of Overhead||Action Type||LMIRCam [sec]||NOMIC [sec]|
|Detector||Fast Mode Full frame|
|Medium Mode Full frame|
|Slow Mode Full frame|
Note that Fast mode has subwindowing. Minimum time scales linearly with vertical pixel length.
The above times are estimates and may be refined. Detector times TBD
Twilight is used for initial AO setup and checkout and for the initial instrument alignment. As a result, start of night set up overheads are therefore not passed on to the users. Calibration frames, such as Darks, are taken during telescope transition states while waiting for the AO to reacquire as another means of increasing observing efficiency. For ALES observations, it is necessary to take the wavelength calibrations before moving any optics to ensure consistent results. It may be necessary to take these during the night depending on the programs. These wavelength calibrations take approximately 20 minutes.