.TH ASTRO 1
.SH NAME
astro \- print astronomical information
.SH SYNOPSIS
.B astro
[
.B -dlpsatokm
]
[
.B -c
n
]
[
.B -C
d
]
[
.B -e
.I obj1
.I obj2
]
.SH DESCRIPTION
.I Astro
reports upcoming celestial events, by default for 24 hours starting now.
The options are:
.TP
.B d
Read the starting date.
A prompt gives the input
format.
.TP
.B l
Read the north latitude, west longitude, and elevation of the observation point.
A prompt gives the input format.
If
.B l
is missing, the initial position is read from the file
.BR /lib/sky/here .
.TP
.B c
Report for
.I n
(default 1) successive days.
.TP
.B C
Used with
.BR -c ,
set the interval to
.B d
days (or fractions of days).
.TP
.B e
Report distance between the centers of
objects, in arc seconds, during eclipses or occultations involving
.I obj1
and
.IR obj2 .
.TP
.B 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, seconds),
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 latitude, longitude, and elevation.
.TP
.B s
Print output in English words suitable for speech synthesizers.
.TP
.B 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.)
.TP
.B 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.
.TP
.B o
Search for stellar occultations.
.TP
.B k
Print times in local time (`kitchen clock')
as described in the
.B timezone
environment variable.
.TP
.B 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).
.SH FILES
.TF /lib/sky/estartab
.TP
.B /lib/sky/estartab
ecliptic star data
.TP
.B /lib/sky/here
default latitude (N), longitude (W), and elevation (meters)
.SH SOURCE
.B \*9/src/cmd/astro
.SH SEE ALSO
.IR scat (1)
.SH BUGS
The
.B k
option reverts to GMT outside of 1970-2036.