Solar eclipse of August 7, 1869

In 1869, astronomer and explorer George Davidson made a scientific trip to the Chilkat Valley of Alaska. He told the Chilkat Indians that he was anxious to observe a total eclipse of the sun that was predicted to occur the following day, August 7. This prediction was considered to have saved Davidson's expedition from an attack.^[2]

A photographic expedition was organized by Philadelphia's Henry Morton under the authority of John H. C. Coffin, U.S.N., Superintendent of the American Ephemeris and Nautical Almanac. The expedition observed the eclipse in Iowa at three stations: Burlington, Mount Pleasant, and Ottumwa, under the respective supervisions of Alfred M. Mayer, Henry Morton, and Charles Francis Himes (1838–1918).^[3]

Observations were also made by meteorology pioneers Cleveland Abbe and General Albert Myer, in Dakota Territory and Virginia, respectively.^[4]

Shown below are two tables displaying details about this particular solar eclipse. The first table outlines times at which the moon's penumbra or umbra attains the specific parameter, and the second table describes various other parameters pertaining to this eclipse.^[5]

This eclipse is part of an eclipse season, a period, roughly every six months, when eclipses occur. Only two (or occasionally three) eclipse seasons occur each year, and each season lasts about 35 days and repeats just short of six months (173 days) later; thus two full eclipse seasons always occur each year. Either two or three eclipses happen each eclipse season. In the sequence below, each eclipse is separated by a fortnight.

• A partial lunar eclipse on January 28.
• An annular solar eclipse on February 11.
• A partial lunar eclipse on July 23.
• A total solar eclipse on August 7.

• Preceded by: Solar eclipse of October 19, 1865
• Followed by: Solar eclipse of May 26, 1873

• Preceded by: Solar eclipse of June 27, 1862
• Followed by: Solar eclipse of September 17, 1876

• Preceded by: Lunar eclipse of August 1, 1860
• Followed by: Lunar eclipse of August 13, 1878

• Preceded by: Solar eclipse of September 7, 1858
• Followed by: Solar eclipse of July 7, 1880

• Preceded by: Solar eclipse of July 28, 1851
• Followed by: Solar eclipse of August 19, 1887

• Preceded by: Solar eclipse of August 27, 1840
• Followed by: Solar eclipse of July 18, 1898

• Preceded by: Solar eclipse of October 7, 1782
• Followed by: Solar eclipse of June 8, 1956

This eclipse is a member of a semester series. An eclipse in a semester series of solar eclipses repeats approximately every 177 days and 4 hours (a semester) at alternating nodes of the Moon's orbit.^[6]

The partial solar eclipses on April 15, 1866 and October 8, 1866 occur in the previous lunar year eclipse set, and the solar eclipses on June 28, 1870 (partial) and December 22, 1870 (total) occur in the next lunar year eclipse set.

This eclipse is a part of Saros series 143, repeating every 18 years, 11 days, and containing 72 events. The series started with a partial solar eclipse on March 7, 1617. It contains total eclipses from June 24, 1797 through October 24, 1995; hybrid eclipses from November 3, 2013 through December 6, 2067; and annular eclipses from December 16, 2085 through September 16, 2536. The series ends at member 72 as a partial eclipse on April 23, 2897. Its eclipses are tabulated in three columns; every third eclipse in the same column is one exeligmos apart, so they all cast shadows over approximately the same parts of the Earth.

The longest duration of totality was produced by member 16 at 3 minutes, 50 seconds on August 19, 1887, and the longest duration of annularity will be produced by member 51 at 4 minutes, 54 seconds on September 6, 2518. All eclipses in this series occur at the Moon’s ascending node of orbit.^[7]

The metonic series repeats eclipses every 19 years (6939.69 days), lasting about 5 cycles. Eclipses occur in nearly the same calendar date. In addition, the octon subseries repeats 1/5 of that or every 3.8 years (1387.94 days). All eclipses in this table occur at the Moon's ascending node.

This eclipse is a part of a tritos cycle, repeating at alternating nodes every 135 synodic months (≈ 3986.63 days, or 11 years minus 1 month). Their appearance and longitude are irregular due to a lack of synchronization with the anomalistic month (period of perigee), but groupings of 3 tritos cycles (≈ 33 years minus 3 months) come close (≈ 434.044 anomalistic months), so eclipses are similar in these groupings.

The partial solar eclipse on October 24, 2098 (part of Saros 164) is also a part of this series but is not included in the table below.

This eclipse is a part of the long period inex cycle, repeating at alternating nodes, every 358 synodic months (≈ 10,571.95 days, or 29 years minus 20 days). Their appearance and longitude are irregular due to a lack of synchronization with the anomalistic month (period of perigee). However, groupings of 3 inex cycles (≈ 87 years minus 2 months) comes close (≈ 1,151.02 anomalistic months), so eclipses are similar in these groupings.

• NASA graphics
  • Googlemap
  • NASA Besselian elements
• Sketch of Solar Corona 1869 August 7
• The Solar Eclipse of 7 August 1869 P 70: Coast Survey Report 1869, 126–127, Cambridge, August 20, 1869
• Observatory, United States Naval (1870). Reports on observations of the total eclipse of the sun, August 7, 1869 (Google eBook).