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Lunar Eclipses as Viewed from Special Collections

September 27, 2015

Tonight’s lunar eclipse, which coincides with what is known as a harvest moon, prompts us to offer several examples of depictions of lunar eclipses from our holdings. (For a more direct view, we refer you to the Department of Astronomy at UW-Madison, which is holding an eclipse-viewing event tonight at Wingra Park: details at http://www.astro.wisc.edu/news-events/events/lunar-eclipse-party-9-27-15/, a Web page better viewed at the moment using a browser other than Chrome.)

Four diagrams of lunar eclipses — both pre-Copernican (Ptolemaic) and Copernican — depict the same heavenly phenomenon as grounded in different cosmological theories.

Leaf c[i] verso, depicting eclipses, in the Ratdolt edition of Sacrobosco's treatise On the sphere (1482). From the Department of Special Collections, Memorial Library, University of Wisconsin-Madison.
Leaf c[i] verso, depicting eclipses, in the Ratdolt edition of Sacrobosco’s treatise On the sphere (1482). From the Department of Special Collections, Memorial Library, University of Wisconsin-Madison.

The first comes from an incunable edition of the long-used, often re-edited medieval text of Sacrobosco (Joannes de Sacro Bosco [Sacrobosco], or John of Holywood, fl. 1230): Ioannis de Sacro Busto Sph[a]ericu[m] opusculu[m] ([Venice]: Impressum … arte & diligentia Erhardi Ratdolt Augustensis, 1482), Special Collections call number: Incunable CA 14939, from the W. Reeder Family Collection. Other images from this volume are available as part of a modest online exhibit “Sacrobosco and his commentators,” containing selected pages and illustrations from each of our editions of the works of Sacrobosco for use in class presentations in the Department of History of Science.

A geocentric view of eclipses, from "Annotationi sopra la sferette," MS 83 (1570), Department of Special Collections, Memorial Library, University of Wisconsin-Madison.
A geocentric view of eclipses, from “Annotationi sopra la sferette,” MS 83 (1570), Department of Special Collections, Memorial Library, University of Wisconsin-Madison.

The second pen-and-ink drawing is from a 16th-century manuscript with wonderful imagery: [Sacrobosco], “Annotationi sopra la sferette” (1570), Special Collections call number: MS 83. Selected images from this 92-leaf work are likewise included in our online exhibit. Here too the diagram depicted a resolutely geocentric universe.

Here, too, the earth occupied the center. From Mauro, Annotationi sopra la lettione della Spera del Sacro Bosco, doue si dichiarano tutti e principii mathematici & naturali, che in quella si possan’ desiderare [Florence, 1550], Department of Special Collections, Memorial Library, University of Wisconsin-Madison.
Here, too, the earth occupied the center. From Mauro, Annotationi sopra la lettione della Spera del Sacro Bosco [1550], Department of Special Collections, Memorial Library, University of Wisconsin-Madison.

In the third set of diagrams shown here, from Mauro’s Annotationi sopra la lettione della Spera del Sacro Bosco, doue si dichiarano tutti e principii mathematici & naturali, che in quella si possan’ desiderare [Florence, 1550], call number: LXCT SA1 A Cutter, the sun lacked the sunny disposition of the sun in our manuscript of 1570. Our online exhibit includes other illustrations from this work.

The fourth diagram, dating from the latter half of the 18th century, represented a popularization of Newtonian ideas, hence thoroughly Copernican in character. The works of James Ferguson (1710-1766), an “accomplished public lecturer and expounder of Newtonian ideas” as described in the Dictionary of scientific biography, found a receptive audience: witness the many editions of his Astronomy explained upon Sir Isaac Newton’s principles, which  first appeared in 1756 (we have editions of 1764, 1794, and 1803, demonstrating the longevity of Ferguson’s exposition). “The Moon when totally eclipsed is not invisible, if she be above the Horizon and the Sky be clear,” as Ferguson described matters, “but appears generally of a dusky colour like tarnished copper.” He also likened the color to that “of iron almost red hot” (p. 193 in the edition of 1764).

The far right of Fig. II shows the geometry of a lunar eclipse. From James Ferguson, Astronomy explained upon Sir Isaac Newton's principle, 3rd ed. (London, 1764).
The far right of Fig. II shows the geometry of a lunar eclipse. From James Ferguson, Astronomy explained upon Sir Isaac Newton’s principles, 3rd ed. (London, 1764).

In his Newtonian astronomy textbook, Ferguson also expounded at length on the harvest moon, noting that farmers in “places of considerable Latitude” appreciated the fact that such a full moon at harvest time gave them “an immediate supply of Moonlight after sun-set for their greater conveniency in reaping the fruits of the Earth” (pp. 135-136). He supplied a table contrasting “Years in which the Harvest-Moons are least beneficial” and “Years in which they are most beneficial”: the table covered more than a century (1751-1861), but stopped well short of 2015.

More of Ferguson’s work is highlighted in the Romantic Circles Gallery, a project that drew upon investigations by students in Prof. Theresa Kelley’s and Prof. Jill Casid’s seminars in 2009.

Several courses offered by the Department of History of Science on campus address the transition from geocentrism to heliocentrism in the period known as the Scientific Revolution: see UW MyCourseGuide for details.

— Robin Rider