Observing overheads

Folding telescope offsets in dithering scripts in to the readout of an exposure has been added. Typically 5-6 sec are now saved per exposure/dither by moving the telescope while reading out after the shutter has closed. This is very useful for short exposures such as twilight sky flats, and bright standards. For 3-10 sec exposures this means that the execution time of a dither is 20-25% shorter. For the ``frame'' command no tests were made yet. In this readout mode, the shutter closes after the last readout, but the file storage time can be considerable (6-7s) and this will be folded into the time needed to offset the telescope.

It was noted that in some cases the displaying of data being readout caused an effective increase in the overheads. For these cases the commands notcam.autoshow_on and _off were made to be able to switch the automatic data displaying during readout on or off. The corresponding commands were also implemented for ALFOSC and StanCam.

A systematic measurement of overheads was made in order to disentangle the different sources of the overheads. The results are described in the NOTCam User's Guide under the section ``What are the overheads?'', see:

http://www.not.iac.es/instruments/notcam/guide/observe.html#overheads

The ultimate solution to the rather particular NOTCam overheads is the arrival of the new controller. The sooner we get the new controller, the sooner NOTCam can show its full capabilities.