A total solar eclipse occurred at the Moon's ascending node of orbit on Monday, July 28, 1851, with a magnitude of 1.0577. A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby totally or partly obscuring the image of the Sun for a viewer on Earth. A total solar eclipse occurs when the Moon's apparent diameter is larger than the Sun's, blocking all direct sunlight, turning day into darkness. Totality occurs in a narrow path across Earth's surface, with the partial solar eclipse visible over a surrounding region thousands of kilometres wide. Occurring about 1.5 days before perigee (on July 30, 1851, at 2:30 UTC), the Moon's apparent diameter was larger. The path of totality was visible from parts of modern-day Canada, Greenland, Iceland, Norway, Sweden, Denmark, Poland, Russia, southwestern Lithuania, Belarus, Ukraine, Moldova, Georgia, Armenia, and Azerbaijan. A partial solar eclipse was also visible for parts of North America, Europe, North Africa, Russia, the Middle East, and Central Asia. This was the earliest scientifically useful photograph of a total solar eclipse, made by Julius Berkowski at the Royal Observatory in Königsberg, Prussia. It was the first occasion that an accurate photographic image of a solar eclipse was recorded.

Background

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.

Monday, July 28, 1851

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. 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. 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.

Eclipse details

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.

Eclipse season

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.

Related eclipses

Eclipses in 1851

Metonic

Tzolkinex

Half-Saros

Tritos

Solar Saros 143

Inex

Triad

Solar eclipses of 1848–1852

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.

Saros 143

Metonic series

All eclipses in this table occur at the Moon's descending node.

Tritos series

Inex series