Q:  Estimate the size of the difference in LST between the  
      observer in Rochester and the observer in Los Angeles.
      What are the natural units?


            Roughly three hours, because Rochester and Los Angeles
            are separated by three time zones.

            For more precision, we can use the longitudes of Rochester
            (77 degrees West) and Los Angeles (118 degrees West) to 
            compute a difference of 

                    (118 - 77)  degrees        41
                   ---------------------  =   -----  hours  =  2.7 hours
                    15 degrees per hour        15


  Q:  What is the sign of quantity 

          (LST_in_Rochester - LST_in_Los_Angeles)


                  When a star is overhead in Rochester, that
                  star hasn't yet reached the meridian in LA;
                  thus, the LST in LA must be smaller.

                     (LST_in_Rochester - LST_in_LA) > 0