Astronomical Programs
A variety of astronomical programs are used within the scripts.
These are based as much as possible using the IAU SOFA routines.
- addiso -adds times to iso date/times
- altaz -converts ra/dec to altitude azimuth
- apparent -computes apparent celestial position
- bulld -IERS earth rotation data files (Delta UT) daemon
- csort -sorts star lists for least travel
- dist -calculates angular distances
- era -prints out the earth rotation angle
- jd -prints out the current Julian date
- lst -prints out the local sidereal time
- moon -prints out the RA and Dec of the moon
- nobaby -converts sexagesimal to decimal
- precess -precesses RA and Dec to different equinoxes
- precrot -determines rotation of ICRS to observed
- sun -prints out the RA and Dec of the sun
- tobaby -converts decimal to sexagesimal
- ut -prints out the current Universal time
- visible -prints if object is with telescope limits
Coordinate Strings
These program make use of what I call
Coordinate strings which have the
following space delimited format:
similar to
ra=12:23:34.4 dec=23:23:34.5 equinox=2000.0 epoch=2017.122 name=ganesh
Earth Orientation and UT1
The programs make use of the current values of the polar position and the
deviation of the UT1 from UTC.
Many of the programs have a nodut option which ignores this small offset.
It does so by pulling off files from the
IERS Prediction Center
occasionally and storing them as:
/var/tmp/mark3.out - Bulletin A predictions
/var/tmp/finals.dat - finale pole data going backwards.
These files are created by the
bulld daemon which should be fired up by startnet.
The are made group writable so that they
may be overwritten as needed.
If the files are not available, zero values are used and a Warning message
is issued by many of the programs.
Many of these issues have nodut options to override this.
You can disable this correction for all programs by placing the setting the
NODUT variable into the environment.
Site and Weather
Some of the astronomical calculations need information about the observing site
and the weather.
This is supplied by two services by either the telescope server using
tel_status
or mets commands or by strings.
Minimal site and weather strings are of the following format:
lat=37.871111 long=-122.050566 elev=82.0
oat=14.5 humidity=0.2 bar=1003.4
Calling index