
ACTION:
 Nutation (IAU 1980 theory): longitude & obliquity components, and mean
obliquity.

CALL:
CALL sla_NUTC80 (DATE, DPSI, DEPS, EPS0)
GIVEN:
DATE  D  TDB (formerly ET) as Modified Julian Date
(JD$$2400000.5) 

RETURNED:
DPSI,DEPS  D  nutation in longitude and obliquity (radians) 

EPS0  D  mean obliquity (radians) 


NOTES:


(1)
 The IAU 1980 theory used in the present function has errors as large as 350 mas
over the interval 19002100, mainly because of the error in the IAU 1976 precession.
For more accurate results, either the corrections published in IERS Bulletin B must
be applied, or the sla_NUTC function can be used. The latter is based upon the more
recent SF2001 nutation theory and is of better than 1 mas accuracy.

(2)
 The distinction between the required TDB and TT is always negligible. Moreover,
for all but the most critical applications UTC is adequate.

REFERENCES:


(1)
 Final report of the IAU Working Group on Nutation, chairman P.K.Seidelmann,
1980.

(2)
 Kaplan, G.H., 1981. USNO circular no. 163, pA36.