Solar eclipse of July 28, 1851

A solar eclipse occurs when the Moon passes between the Earth and the Sun, casting a shadow on Earth that temporarily obscures part or all of the Sun's disc. Eclipses can occur only when all three bodies are properly aligned. Partial eclipses, in which only a portion of the Sun's surface is obscured, are relatively common due to the width of the Moon's outer shadow, or penumbra, which may be several hundred miles wide. Total eclipses occur when the Moon's inner shadow, or umbra, reaches the surface of the Earth, completely obscuring the Sun over a much narrower portion of the ground. If the Moon is too far away at the time of an eclipse, its umbra may not reach the Earth's surface, and only a partial eclipse will be visible.

Before the advent of modern science, solar eclipses were often viewed with superstitious dread. However, eclipses are also of interest to science due to the various phenomena that can be observed when they occur. The Sun's outer atmosphere, or corona, is normally invisible due to the brightness of the solar disc, but becomes visible from Earth during a total eclipse. Until the twentieth century, solar eclipses provided the only opportunity for scientists to observe and study the Sun's corona. With the development of photography during the first half of the nineteenth century, it became theoretically possible to record a still image of the Sun during a total eclipse. A variety of processes were used for early photographs, of which the most successful was the daguerreotype.

Photographing a rare event such as a total eclipse posed unique challenges for early photography, including the extreme contrast between the corona and the dark shadow of the Moon, as well as the unusual angle to which photographic equipment had to be oriented. Prior to the eclipse of July 28, 1851, no properly exposed photograph of the solar corona had yet been produced. For this occasion, the Royal Prussian Observatory at Königsberg (now Kaliningrad, Russia) commissioned one of the city's most skilled daguerreotypists, Johann Julius Friedrich Berkowski, to record a still image of the event.^[2] The observers attached a small six-centimeter refracting telescope to a 15.8 centimeter Fraunhofer heliometer, and Berkowski made an eighty-four second exposure shortly after the beginning of totality.^[3]

Among the other observers were British astronomers Robert Grant and William Swan, and Austrian astronomer Karl Ludwig von Littrow. They deduced that prominences were part of the Sun, because the Moon was seen to cover and uncover them as it moved in front of the Sun.^{[4][better source needed]}

•  
  From Gdańsk
•  
  Partial from Shelbyville, Kentucky

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 17.
• An annular solar eclipse on February 1.
• A partial lunar eclipse on July 13.
• A total solar eclipse on July 28.

• Preceded by: Solar eclipse of October 9, 1847
• Followed by: Solar eclipse of May 16, 1855

• Preceded by: Solar eclipse of June 16, 1844
• Followed by: Solar eclipse of September 7, 1858

• Preceded by: Lunar eclipse of July 22, 1842
• Followed by: Lunar eclipse of August 1, 1860

• Preceded by: Solar eclipse of August 27, 1840
• Followed by: Solar eclipse of June 27, 1862

• Preceded by: Solar eclipse of July 17, 1833
• Followed by: Solar eclipse of August 7, 1869

• Preceded by: Solar eclipse of August 16, 1822
• Followed by: Solar eclipse of July 7, 1880

• Preceded by: Solar eclipse of September 25, 1764
• Followed by: Solar eclipse of May 29, 1938

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 3, 1848 and September 27, 1848 occur in the previous lunar year eclipse set, and the solar eclipses on June 17, 1852 (partial) and December 11, 1852 (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 descending 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.

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 chart graphics
  • Googlemap
  • NASA Besselian elements
• Axel D. Wittmann (2005). Development of Solar Research: Proceedings of the Colloquium, Freiburg (Breisgau), September 15, 2003. Deutsch. p. 128. ISBN 978-3-8171-1755-0.^{[permanent dead link]}
• FIRST SUN PHOTO
• On the Berkowski Daguerreotype (Konigsberg, 1851 July 28): The First Correctly Exposed Eclipse Photograph of the Solar Corona
• From eclipse drawings to the coronagraph and spectroscopy
• History of Astrophotography Timeline
• Sketch of Solar Corona 1851 July 28
• Solar eclipse of July 28, 1851 in Russia Archived May 21, 2009, at the Wayback Machine