***** File EPHINFO.TXT                                                        
                                                                              
     This brief information file is located in the EPHEM directory, which     
contains ephemeris information for comet P/Halley.  The ephemeris was         
generated by Donald K. Yeomans as described in the file EPHEM.TXT.  The actual
data are provided in the table file EPHEM.TAB, which contains fully-perturbed,
daily ephemerides for the interval 1981 November 26 -- 1989 June 23.  An      
interpolation program in the SOFTWARE directory of this disc allows accurate  
ephemeris data to be generated within a UT day using EPHEM.TAB as input.  The 
source code is called OBSNTERP.FOR, and MS-DOS- and VAX/VMS-based executables 
are PCNTERP.EXE and VAXNTERP.EXE, respectively.  A description of this        
software and how to use it can be found in the file OBSNTERP.TXT, located in  
both the DOCUMENT and SOFTWARE directories of this disc.                      
                                                                              
     Ephemerides have also been deposited in the data subdirectories of this  
disc, in files called EPHMINFO.TXT.  The time range of each of these files    
matches that of the particular subdirectory in which it is placed.  It was    
hoped that the EPHMINFO.TXT files would be useful to archive users who, while 
browsing through the data subdirectories, did not wish to open the large table
EPHEM.TAB to obtain ephemeris information for a very short time range.  The   
format of the tabular display (in EPHMINFO.TXT) is slightly different from    
that of EPHEM.TAB, in that in addition to right ascension and declination, the
hourly rates of change of those parameters are provided.