IAU (1976) System of Astronomical Constants

The International Astronomical Union at its 16th General Assembly in Grenoble in 1976, accepted Resolution No. 1{{Citation

| editor-last=Müller | editor-first=Edith A.

| editor2-last=Jappel | editor2-first=A.

| year=1977

| title=Proceedings of the Sixteenth General Assembly Grenoble 1976

| series=Transactions of the International Astronomical Union

| section=Resolution No. 1

| volume=16B

| page=31

| url=https://archive.org/details/proceedingsofsix0016inte/page/31/

| publisher=D. Reidel

| place=Dordrecht, Holland

| isbn=90-277-0836-3

}} regarding a "New System of Astronomical Constants"{{Citation

| editor-last=Müller | editor-first=Edith A.

| editor2-last=Jappel | editor2-first=A.

| year=1977

| title=Proceedings of the Sixteenth General Assembly Grenoble 1976

| series=Transactions of the International Astronomical Union

| section=Report of Joint Meeting of Commissions 4, 8, 31 on the New System of Astronomical Constants

| volume=16B

| pages=52–67

| url=https://archive.org/details/proceedingsofsix0016inte/page/52/

| publisher=D. Reidel

| place=Dordrecht, Holland

| isbn=90-277-0836-3

}}. Refer to subsection "Recommendations to IAU General Assembly, 1976" on pages 58-61 for specific values. recommended for reduction of astronomical observations, and for computation of ephemerides. It superseded the IAU's previous recommendations of 1964 (see IAU (1964) System of Astronomical Constants), became in effect in the Astronomical Almanac from 1984 onward, and remained in use until the introduction of the IAU (2009) System of Astronomical Constants. In 1994

{{Citation | editor-last=Appenzeller | editor-first=I | contribution=IAU (1994): Proceedings of the 22nd General Assembly, XXII B | series=Transactions of the IAU | year=1994 | publisher=Kluwer Academic | contribution-url=http://www.iau.org/static/resolutions/IAU1994_French.pdf | isbn=0-7923-3842-1 | title=Transactions of the International Astronomical Union: Proceeding of the Twenty-Second General Assembly, the Hague 1994 }}

the IAU recognized that the parameters became outdated, but retained the 1976 set for sake of continuity and also recommended to start maintaining a set of "current best estimates".IAU(1994) ibidem, Resolution No. C 6 This "sub group for numerical standards" had published a list, which included new constants (like those for relativistic time scales).

{{citation|author=Standish, E.M. |contribution=Report of the IAU WGAS Sub-group on Numerical Standards |url=http://iau-comm4.jpl.nasa.gov/iausgnsrpt.pdf |title=Highlights of Astronomy |editor=Appenzeller, I. |location=Dordrecht |publisher=Kluwer |year=1995 |url-status=dead |archive-url=https://web.archive.org/web/20120907165000/http://iau-comm4.jpl.nasa.gov/iausgnsrpt.pdf |archive-date=2012-09-07 }}

The system of constants was prepared

{{cite journal | last=Seidelmann | first=P. Kenneth | title=Numerical values of the constants of the Joint Report of the Working Groups of IAU Commission 4 | journal=Celestial Mechanics | volume=16 | pages=165–177 | date=1977 | issue=2 | doi=10.1007/BF01228598 | url=http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1977CeMec..16..165S&link_type=ARTICLE | bibcode=1977CeMec..16..165S| s2cid=123361221 }}

by Commission 4 on ephemerides led by P. Kenneth Seidelmann after whom asteroid 3217 Seidelmann is named.

At the time, a new standard epoch (J2000.0) was accepted; followed later

{{Citation | editor-last=Wayman | editor-first=P. | contribution=IAU (1979): Proceedings of the 17th General Assembly, XVII B | series=Transactions of the IAU | year=1980 | publisher=D.Reidel | place=Dordrecht | contribution-url=http://www.iau.org/static/resolutions/IAU1979_French.pdf | isbn=90-277-1159-3| title=Transactions of the International Astronomical Union, Volume XVIIB }}

{{Citation | editor-last=West | editor-first=R | contribution=IAU (1982): Proceedings of the 18th General Assembly, XVIII B | series=Transactions of the IAU | year=1982 | publisher=D.Reidel | place=Dordrecht | contribution-url=http://www.iau.org/static/resolutions/IAU1982_French.pdf | isbn=0-7923-3842-1 | title=Transactions of the International Astronomical Union: Proceeding of the Twenty-Second General Assembly, the Hague 1994 }}

by a new reference system with fundamental catalogue (FK5), and expressions for precession of the equinoxes,

and in 1979 by new expressions for the relation between Universal Time and sidereal time,IAU(1979) ibidem, recommendation by Commissions 4 (Ephemerides), 8 (Positional Astronomy), 19 (Rotation of the Earth), 31 (Time)

{{cite journal | last=Lederle | first=Trudpert | title=The IAU (1976) System of Astronomical Constants | journal=Mitteilungen des Astronomisches Gesellschaft | volume=48 | pages=59..65 | date=1980 | url=http://articles.adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1980MitAG..48...59L&link_type=ARTICLE | bibcode=1980MitAG..48...59L}}

IAU(1982) ibidem, Resolution No. C 5 and in 1979 and 1980 by a theory of nutation.IAU(1979) ibidem, recommendation by Commissions 4 (Ephemerides), 19 (Rotation of the Earth), 31 (Time)IAU(1982) ibidem, Resolution No. R 3 There were no reliable rotation elements for most planets, but a joint working group on Cartographic Coordinates and Rotational Elements was installed to compile recommended values.{{Citation

| editor-last=Müller | editor-first=Edith A.

| editor2-last=Jappel | editor2-first=A.

| year=1977

| title=Proceedings of the Sixteenth General Assembly Grenoble 1976

| series=Transactions of the International Astronomical Union

| section=Commision 4: Ephemerides, Report of Meeting 25 August 1976

| volume=16B

| pages=49–52

| url=https://archive.org/details/proceedingsofsix0016inte/page/49/

| publisher=D. Reidel

| place=Dordrecht, Holland

| isbn=90-277-0836-3

}}. See page 50, specifically.IAU(1979) ibidem, recommendation by Commissions 4 (Ephemerides) and 16 (Physical Study of Planets and Satellites)