In addition, the user may choose to be prompted for the required filter position, and the user may also choose to be be prompted for the required telescope focus setting. (How to do this will be explained when we discuss the obspars parameter file in Section 3.3.) If so, the filter wheel will be moved to the requested position and/or the telescope set to the requested focus setting before continuing.
An example of taking a 300 second ``object" exposure is shown in Figure 1. Note that in each query the user is also presented with a default value that s/he could invoke simply by hitting [CR]; these default values are just the previous entries. Once the title is entered, the user is informed what the name of the image will be; this name consists of a root (``n1" in this example), plus a number which is automatically incremented on each exposure until reset by the user.
If all goes well, the user will be given a one-line ``status" report, then told that the chip is ``preparing", followed by ``exposing". If the exposure is long enough, the astronomer is also shown both the time left to expose and the amount already exposed; these update at sec intervals, as do the temperature of the CCD (Tcam) and the temperature of the dewar (Tdew). (The dewar temperature will begin to increase if the liquid nitrogen is used up; keep an eye on this number and call for help if it goes up by two degrees.) Finally, the user will be informed when the chip is reading out. Read-out time for our chips varies, but can be several minutes for the largest, so be patient. Finally the user is told that the image has been written to disk.
NOTE: All observing commands must be issued from the ``DATA ACQUISITION window" and NOT from the ``DATA REDUCTION" window. We will describe these windows in Section A.2.
The actual steps that occur during an ``observe" sequence are listed in Sec. N