Nutation In Ecliptical Longitude (ΔΨ) and Right Ascension (ΔRA)
Date:     ±Y  m  d Time:   H M S       UT ±ΔT:      H M S
Calendar Mode: Julian   Gregorian 

Algorithm To Compute The Nutation In Longitude (dPsi)

The following algorithm computes the nutation in ecliptical longitude, in degrees, for a given JD argument.   It is is based on the 1980 IAU Theory of Nutation and Reduction.

This value is the correction to apply to the MEAN value of the ecliptical longitude to obtain the TRUE longitude, with a theoretical precision of ±0.001 arc sec.

Any trigonometric functions (sin, cos, tan, et al.) used in the pseudo-code, assume radian arguments unless otherwise indicated.   In this case, the final result is being converted into degrees for convenience.

Ref:
Astronomical Algorithms - 2nd Edition (1998)
Jean Meeus
Pub. Willmann-Bell, Inc.
ISBN 0-943396-61-1

Ref:
Explanatory Supplement to the Astronomical Almanac (1992)
p111 to p114
ISBN 0-935702-68-7

WikiRef:
http://en.wikipedia.org/wiki/Nutation


Elements
JDGeneral JD number for given date, time and ΔT
TTime factor in Julian centuries reckoned from J2000.0, corresponding to JD
 DegToRad This is a conversion factor used to convert degrees into equivalent radians.  We multiply degrees by this factor to obtain the equivalent angle expressed in radians.  Not every programming language has functions to convert between radians and degrees.
wNutation series accumulator (arc seconds x 10000).
w1Mean elongation of the moon from the sun.
w2Mean solar anomaly.
w3Mean lunar anomaly.
w4Lunar argument of latitude.
w5Longitude of ascending node of lunar orbit on the ecliptic as measured from the mean equinox of date.
dPsiDegNutation in ecliptical longitude expressed in degrees.
 Algorithm to compute nutation in ecliptical longitude (dPsiDeg) for a given JD argument.



 PHP function to compute nutation in ecliptical longitude (dPsi) for a given JD argument.




 CPP function to compute nutation in ecliptical longitude (dPsi) for a given JD argument.



 VB.NET function to compute nutation in ecliptical longitude (dPsi) for a given
JD argument
.



© Jay Tanner - PHP Science Labs - 2017 - v1.6