julian.texi

\input texinfo
@c julian.mac Copyright 2016 Nicholas C. Strauss (strauss@positive-internet.com)
@c
@c   This program is free software: you can redistribute it and/or modify
@c   it under the terms of the GNU General Public License as published by
@c   the Free Software Foundation, either version 3 of the License, or
@c   (at your option) any later version.
@c
@c   This program is distributed in the hope that it will be useful,
@c   but WITHOUT ANY WARRANTY; without even the implied warranty of
@c   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
@c   GNU General Public License for more details.
@c
@c   You should have received a copy of the GNU General Public License
@c   along with this program.  If not, see <http://www.gnu.org/licenses/>
@c
@c   Low precision ephemeris for the Sun.
@c   Source: Explanatory Supplement to the Astronomical Almanac
@c   P. Kenneth Seidelmann, United States Naval Observatory.
@c   Nautical Almanac Office, Great Britain. Nautical Almanac Office
@c

@setfilename julian.info
@settitle julian

@ifinfo 
@macro var {expr}
<\expr\>
@end macro
@end ifinfo

@node Top, Introduction to julian, (dir), (dir)
@top
@menu
* Introduction to julian::
* Definitions for julian::
* Function and variable index::
@end menu
@chapter julian

@node Introduction to julian, Definitions for julian, Top, Top
@section Introduction to julian

@code{julian} returns the number of elapsed days since January 1, 4713 BC. Note that
the conventional calendar changed in October 1582 due to the adoption of the Gregorian calendar. 
The algorithm is based on Peter Duffett-Smith ``Astronomy with your personal computer'', 
2nd edition. In this algorithm, there is no year 0 B.C. The Macsyma tests is from Jean Meeus 
``Astronomical Algorithms'', which uses a year 0 B.C. convention. Users should be careful
when using years <=0.

@node Definitions for julian, Function and variable index, Introduction to julian, Top
@section Definitions for julian

@deffn {Function} julian(@var{day}, @var{month}, @var{year})
Returns the Julian day number.
@end deffn
@deffn {Function} modified_julian(@var{day}, @var{month}, @var{year})
Returns a modified Julian day number that is offset by 2.4 million days.
@end deffn
@deffn {Function} julian1900(@var{day}, @var{month}, @var{year})
Returns the number of Julian days since 1900 A.D.
@end deffn
@deffn {Function} julian1904(@var{day}, @var{month}, @var{year})
Returns the number of Julian days since 1904 A.D.
@end deffn
@deffn {Function} iso8601(@var{day}, @var{month}, @var{year})
The iso8601 standard and the proleptic Gregorian calendar,
extends the Gregorian calendar backward from 1582. Julian days start at noon in Greenwich on November 24, 4714 B.C.
@end deffn
@deffn {Function} calendar(@var{julianDay})
Returns the [day, month, year] given a Julian day number.
@end deffn
@deffn {Function} calendar8601(@var{julianDay})
Returns the [day, month, year] given a iso8601 day number.
@end deffn
@deffn {Function} emacs_absolute_day(@var{day}, @var{month}, @var{year})
Returns an emacs day number given day, month, year.
@end deffn
@deffn {Function} centuries_j2000(@var{jd})
Returns the number of centuries since 1 January 2000.
@end deffn
@deffn {Function} sind(@var{x})
Returns sin of the argument given in degrees.
@end deffn
@deffn {Function} cosd(@var{x})
Returns cos of the argument given in degrees.
@end deffn

@defvr{Variable} day
The day of the month.
@end defvr 
@defvr{Variable} dec
Declination in degrees.
@end defvr 
@defvr{Variable} E
Equation of time in minutes.
@end defvr 
@defvr{Variable} jd
Julian day number.
@end defvr 
@defvr{Variable} julianDay
Julian day number.
@end defvr 
@defvr{Variable} month
month of year.
@end defvr 
@defvr{Variable} T
(Fractional) number of centuries since 1 January 2000.
@end defvr 
@defvr{Variable} UT
Universal time in hours.
@end defvr 
@defvr{Variable} year
Year number.
@end defvr 

@node Function and variable index, , Definitions for julian, Top
@appendix Function and variable index
@printindex fn
@printindex vr

@bye