ASTRO(7)                                                 ASTRO(7)

     NAME
          astro - print astronomical information

     SYNOPSIS
          astro [ -dlpsatokm ] [ -c n ] [ -C d ] [ -e obj1 obj2 ]

     DESCRIPTION
          Astro reports upcoming celestial events, by default for 24
          hours starting now.  The options are:

          d    Read the starting date.  A prompt gives the input for-
               mat.

          l    Read the north latitude, west longitude, and elevation
               of the observation point.  A prompt gives the input
               format.  If l is missing, the initial position is read
               from the file /lib/sky/here.

          c    Report for n (default 1) successive days.

          C    Used with -c, set the interval to d days (or fractions
               of days).

          e    Report distance between the centers of objects, in arc
               seconds, during eclipses or occultations involving obj1
               and obj2.

          p    Print the positions of objects at the given time rather
               than searching for interesting conjunctions.  For each,
               the name is followed by the right ascension (hours,
               minutes, seconds), declination (degrees, minutes, sec-
               onds), azimuth (degrees), elevation (degrees), and
               semidiameter (arc seconds).  For the sun and moon, the
               magnitude is also printed.  The first line of output
               presents the date and time, sidereal time, and the lat-
               itude, longitude, and elevation.

          s    Print output in English words suitable for speech syn-
               thesizers.

          a    Include a list of artificial earth satellites for
               interesting events.  (There are no orbital elements for
               the satellites, so this option is not usable.)

          t    Read ΔT from standard input.  ΔT is the difference
               between ephemeris and universal time (seconds) due to
               the slowing of the earth's rotation.  ΔT is normally
               calculated from an empirical formula.  This option is
               needed only for very accurate timing of occultations,
               eclipses, etc.

     Page 1                       Plan 9            (printed 10/24/25)

     ASTRO(7)                                                 ASTRO(7)

          o    Search for stellar occultations.

          k    Print times in local time (`kitchen clock') as
               described in the timezone environment variable.

          m    Includes a single comet in the list of objects.  This
               is modified (in the source) to refer to an approaching
               comet but in steady state usually refers to the last
               interesting comet (currently Hale-Bopp, C/1995 O1).

     FILES
          /lib/sky/estartab  ecliptic star data
          /lib/sky/here      default latitude (N), longitude (W), and
                             elevation (meters)

     SOURCE
          /sys/src/cmd/astro

     SEE ALSO
          scat(7)

     BUGS
          The k option reverts to GMT outside of 1970-2036.

     Page 2                       Plan 9            (printed 10/24/25)