Tetrad (astronomy)

In astronomy, a tetrad is a set of four total lunar eclipses within two consecutive years.^[1]

Inex and saros for tetrads between AD 1000 and 2500, showing the tetradia

The frequency of tetrads varies by century with the frequency of total lunar eclipses. This repeating cycle is called a tetradia. See Eclipse cycle for more information.

List of tetrad events

1949–2000

Saros	Date Viewing	Type Chart		Saros	Date Viewing	Type Chart
1949–50
Descending node				Ascending node
121	1949 Apr 13	Total		126	1949 Oct 07	Total
131	1950 Apr 02	Total		136	1950 Sep 26	Total
1967–68
Descending node				Ascending node
121	1967 Apr 24	Total		126	1967 Oct 18	Total
131	1968 Apr 13	Total		136	1968 Oct 6	Total
1985–86
Descending node				Ascending node
121	1985 May 04	Total		126	1985 Oct 28	Total
131	1986 Apr 24	Total		136	1986 Oct 17	Total

2001–51

Saros	Date Viewing	Type Chart		Saros	Date Viewing	Type Chart
2003–04
Descending node				Ascending node
121	2003 May 16	total		126	2003 Nov 09	total
131	2004 May 04	total		136	2004 Oct 28	total
2014–15
Ascending node				Descending node
122	2014 Apr 15	Total		127	2014 Oct 08	Total
132	2015 Apr 04	Total		137	2015 Sep 28	Total
2032–33
Ascending node				Descending node
122	2032 Apr 25	Total		127	2032 Oct 18	Total
132	2033 Apr 14	Total		137	2033 Oct 08	Total
2043–44
Descending node				Ascending node
123	2043 Mar 25	Total		128	2043 Sep 19	Total
133	2044 Mar 13	Total		138	2044 Sep 07	Total
2050–51
Ascending node				Descending node
122	2050 May 06	Total		127	2050 Oct 30	Total
132	2051 Apr 26	Total		137	2051 Oct 19	Total

See also

• Total penumbral lunar eclipse § Summary frequency of total penumbral, total umbral and tetrad events 501–2500 for statistics by century
• Blood moon prophecy Apocalyptic preaching of John Hagee and Mark Biltz in part based on the observed phenomenon.