Template program for extracting USNO-A entries in something like a square
around a specific RA/Dec and size.

   1) hms.f is relatively tolerant about accepting decimal, sexagesimal, etc.
      coordinates, but does not understand everything.

   2) eatit.f knows where the catalog is.  It assumes that it is all out
      on a single disk.  You may need to hack it to understand about
      small disks or CD-ROMs.

   3) cio.c does the explicit conversion to BIG_ENDIAN on the read (and write)
      since it was written on a DEC Alpha.  You may need to comment that
      portion of the code out if your native mode is BIG_ENDIAN.

   4) saveit.f doesn't do much more than scribble the USNO-A native
      integers.  You may wish to hack this routine to save things in
      a more useful format.

Please remember that the native USNO-A integers are in the following format.

      (decimal RA)*15*3600*100
      ((decimal DEC)+90)*3600*100    (==SPD==south polar distance)
      SQFFFBBBRRR
          S = sign is - if corresponding entry in GSC + if no entry
          Q = quality is 1 if mags are probably wrong, 0 if probably OK
          FFF = field of original detection.  POSS-I MLP numbers start at
                1 at the north pole and end at 937 in the -30 zone.  Southern
                fields start at 1 at the south pole and end at 408 in the
                -35 zone.  The following test should work:

                IF ((zone.le.600).and.(field.le.408)) THEN
                  south(field)
                ELSE
                  north(field)
                ENDIF

          BBB = 10 times the blue (O or J) mag
          RRR = 10 times the red (E or F) mag

USNO-A is divided into 24 zones of SPD each of width 7.5 degrees.  The
file names integers of SPD*10.
