At the very beginning of your observing run, you should clean off all of the previous observer's images and files, and reinitialize all of ICE and IRAF to the default values. You or the instrument assistant can accomplish this by the following:
The reason for the above procedure is that you cannot have IRAF running during an obsinit or parameters will not be correctly reset. Make sure that you have logged out of each IRAF window before running obsinit.
The obsinit command will also allow you to specify which CCD you are using, and will automatically set the correct telescope identification; both of these are crucial for correct operation. An example of using obsinit is given in Figure 9. Note that the user has the option of selecting whether CNTL-z or CNTL-d will be the default for an end-of-file command; the former is the standard at NOAO, but the latter is the standard at many other places. Finally, note that it is possible to run obsinit WITHOUT deleting any files or images! If you simply wish to set all of the ICE parameters back to their default values, you may run this in the middle of your observing run without losing any files.