If the observatory is already open it returns immediately without doing anything. It then tries the slit, if it is NOT possible to open the script turns off the telescope power, so that the telescope will not track up against a limit and returns a non-zero exit code.
If the sun is higher than ten degree above the horizon, openup will print an error message and exit with an non-zero exit code.
It also executes the zero, focus.csh, or tx dzero procedures if the flags are not set to 1. When each task is completed, it sets the flag to 1. Note: for proper operation the XVista symbol table should be erased daily (this is done by daily.csh). Some e.g. acquire may reset these symbols to zero.
The procedure also checks the number of times the slit has been opened It will not open the slit if this count exceeds ten.