Illustrating Astronomy: E.L. Trouvelot at HCO

Celestial photography often stands as the legacy of the Harvard College Observatory in its early years. But its directors still recognized the value of old-fashioned observations of a human eye in real time. To assist their work at the telescope, they tended to hire assistants trained in astronomy and skilled in mathematics. But Joseph Winlock, director in 1872, recognized the talents and abilities of someone who might utilize the telescope in a different way. Etienne Léopold Trouvelot, an artist and at-home scientist studying worms and moths, had circulated detailed sketches of insects that impressed the Boston science community. This, in addition to scientific observations of the sun that Trouvelot had submitted to various Boston newspapers, brought the name to Winlock of a man with the skill to reproduce the beauty of the most majestic sights in the sky in vibrant color.

Fig. 1: Etienne Leopold Trouvelot (Courtesy UC Santa Cruz, Special Collections)

Trouvelot had come to America from France in 1857, first taking up residence in Medford, MA. He listed his official profession as “lithographer” and he considered his pencil “to be his only resource to support his family” (BSNH Archives). Trouvelot was initially interested in silkworms, and the life-cycles of moths and butterflies. He made a living around Boston with commissioned insect sketches for the prominent scientists in the Boston Society for Natural History, such as Samuel Hubbard Scudder, but he also had scientific pursuits of his own. His work with the American Silkworm aimed to produce a strong and workable silk — ostensibly to relieve the cotton scarcity due to the disrupted trade lines during the Civil War. To engineer a stronger fiber, Trouvelot began to cross-breed the various silkworms, and imported many similar moth species for experimentation, including the Lymantria dispar dispar, the European Gypsy Moth, from France.

Noble intentions, but this was a terrible idea. The gypsy moth had a reputation of resilience, speed, and a voracious appetite, practically able to eat up trees and groves overnight. It was an unwelcome pest. The United States had a somewhat rigid customs procedure at the time, through which Trouvelot had to declare his specimens for inspection. According to the story, Trouvelot never intended to work with dispar eggs, but his supplier had accidentally included a sample, which went unnoticed until Trouvelot returned to Boston.

Fig 2: The American Silkworm, From The American Naturalist, Vol. 1, 1867; Sketched by Trouvelot.

What happened next would extend Trouvelot’s name into infamy, and remains his most resonant memory today. In 1869, the moth escaped his insectary and went on to terrorize the agriculture of North America for the next hundred years and on. Trouvelot immediately realized the horror of the situation when he couldn’t find the larvae — his neighbors later reported him frantically searching around the grass in his yard. He contacted his colleagues at the Boston Society for Natural History, but there was little that could be done, save for a massive extermination campaign (which was attempted on many fronts, see Spear (2006)). No doubt embarrassed, Trouvelot shifted the focus of his career to the world outside of his own, where his observations and theories might impact life a little more softly. He still kept his insectary as hobby, and even returned to publish on insect antennae in 1877.

Fig. 3: Plate 3: The Sun, compiled from several dates (detail, from Annals Vol. 8)

The shift to astronomical work was not a sudden about face. Trouvelot had a small 6-inch telescope that he used regularly, observing planets, nebulae, and even the sun from his backyard. But when Winlock offered him employment at Harvard in 1872, he gained access to the Observatory’s 15-inch refractor, with which he could see objects in far greater detail. The major project that Winlock assigned Trouvelot was to create a series of plates that “represent, as nearly as possible, the most interesting objects in the heavens” as seen through the powerful instruments of the Observatory. These plates were published in 1876, at the end of Trouvelot’s term at Harvard, in Volume VIII of the Annals of Harvard College Observatory. They include prints of Jupiter, Saturn, Mars, great nebulae and comets, as well as sunspots and solar flares, the corona in an eclipse, and detailed views of mountains and craters on the moon.

The final products were selected and perfected from over 1,000 different sketches Trouvelot made at the observatory (most of which are lost or scattered with his various collections around the United States and France). But these images were selected for their beauty, and the way that they combined the immediate wonder of seeing celestial objects with the detail and nuance of extended observation. If, as Trouvelot noted in his research, the clouds of Jupiter change after every glance, the best way to make an image of the planet would be a synthetic representation of its motion and movement. Trouvelot was fond of this sort of time-lapse technique, where he might include many different, but still accurate, observations together in one image (Fig. 3). He mentions in his Drawings Manual (1882) that this was in effort to “give an idea” of the experiences and grandeur of seeing astronomical events in totality.

Fig 4: Plate 8: Solar Prominences (detail, from Annals Vol. 8)

Trouvelot’s second task at the observatory, and the work that earned him a daily wage, was to watch the sun for the spots, and the skies for aurorae. Daily, he would scan the sun and observe spots and prominences, recording notes in a logbook. He would sketch these objects using a contraption built by Winlock, which would project the image of the sun, without reflection, onto a large sheet of paper, from which Trouvelot could accurately map the location, movement, and growth of sunspots. In a similar process, Trouvelot regularly used projections from the telescope to provide outlines for his sketches. One plate from the Annals shows how Trouvelot sketched the Trifid Nebula, by projecting the image onto a reticulated piece of glass over which he would put his own sketch paper. This ensured the accurate shape that astronomers were after, as if they were looking through a telescope on the page (Fig 5-6).

Fig. 5: Plate X: Trifid Nebula Draft (From Annals Vol. 8)

Fig. 6: Plate 32: Trifid Nebula (from Annals Vol. 8)

While Trouvelot sketched, other astronomers at Harvard were busy taking photographs of the sun. Unfortunately neither many of the sketches nor the photographs of the sun remain with the observatory today (Fig. 7). But their functions aimed to be complementary. In 1872, when Trouvelot began at the HCO, photography was still a young art, and the images could not often resolve or translate the fine detail seen through the eyepiece of a powerful telescope. Nor could they relate color, unless modified after the development process. Trouvelot’s daily sketches could capture these details for scientific reference, and his final artistic products could synthesize these moments into a soft, colorful, and total representation of alien phenomena.

Fig. 7: Sketch of sunspots (from the Trouvelot Astronomical Notebook, Houghton Library)

So implicated in performing astronomical science, Trouvelot also read a wide array of scientific literature, and contributed his own observations to the dialogue. Like other astronomers of the day, he was keen to stay abreast of unprecedented observations, discoveries, and theoretical arguments emerging from observatories across the world. In his readings, he was especially interested in the occurrence and appearance of aurorae around the globe. His logbooks, some of which remain as part of Project PHaEDRA, contain indices of aurorae and references to their announcements world-wide during the early years of the 1870s. At night, Trouvelot had a plethora of sights to see, and he always kept an eye out for the northern lights (Fig. 8). On one February night, he recorded in his logbook that “a strong light, carmine red, with a little vermillion mixture” appeared high in the sky . He follows his observations with references to news of storms, magnetic instabilities and other strange phenomena across the globe. This was the Great Aurora of February 4, 1872, the result of one of the most intense magnetic storms in recent scientific memory (Silverman (2008)).

Fig 8: Aurora Borealis, Observed March 1, 1872, at 9:25 pm (from Trouvelot Astronomical Drawings)

The moon also captivated Trouvelot’s eye, and he spent many hours at night making detailed sketches of her craters and mountains (Fig. 9). Even before his time at HCO, he filled sketchbooks with pencil drawings of lunar features and topography, one of which is kept in the care of Houghton Library at Harvard. Trouvelot’s moon drawings influenced many in the arts and sciences: Chesley Bonestell, the famous artist who worked with NASA to promote the U.S.A. in the Space Race of the 1960’s, cited Trouvelot as an inspiration for his fantastic moonscapes; and the International Astronomical Union named a lunar crater after Trouvelot (one on Mars too) (Adamo (2016)).

Fig 9: Plate 4: Moon Craters (detail, from Annals Vol. 8)

As expected from a former entomologist in astronomy, Trouvelot never found one topic on which to specialize his research. His eye for aesthetics made something worth saying out of every object. The most common structural feature on which he comments is the color and cloudy gradients that swirl around in celestial objects. He was not the first person to observe color, but his special eye, in conjunction with his hand, could translate such an image out of the telescope with far more detail and vibrancy than any other contemporary method. But in his publications, often appearing without illustrations, he had to rely on a textual description of color, which he used to vividly recreate the object, interrogate it, and read new conclusions about the stars.

He published on the rings of Saturn, noting the fine gradients of color between and inside the various ring structures, “slate-grey, luminous white, dark black, darker black, and black with a bluish-purple tinge.” From these subtle differences, he concludes that there must be matter, not void, in the dark ‘Cassini Gap’ (Fig. 10-11).

Fig 10: Plate 16: Saturn (detail, from Annals Vol 8)

Fig. 11: The rings of Saturn, showing the details and variations of color. Photographed by Cassini in 2017. (Image courtesy NASA/JPL)

Saturn itself (“of which I have little to say”), barely interested Trouvelot beyond the faint poof and swell of the “golden brown” clouds. And that was nothing compared to the sort of meteorological activity that Trouvelot observed on Jupiter. He writes about storms that form and transverse the planet in the course of a night, changing hues “from rosy pink, to orange, to gray and black smoke.” (Fig. 12-13, 22) Fascinated by the red spot and other cyclones, Trouvelot related Jupiter to the sun, a body so thick with stormy atmosphere, “with years of great calm and years of great disturbance.”

Fig. 12: Plate 1: Jupiter (detail, from Annals Vol. 8)

Fig. 13: The storms of Jupiter. Photographed by Juno in 2017 (Courtesy NASA).

The sun was Trouvelot’s object of greatest celestial interest, especially the spots that marked its surface (Fig. 14-15). While at Harvard, he observed faint spots not unlike an average sun-spot, but obscured as if by clouds. He termed these “veiled spots” and theorized their nature, similar to typical sunspots, but existing on a layer of solar matter below the surface gasses, which happened to be weak and transparent in the present solar cycle. Modern solar science has not has not recognized this phenomenon as a unique event, but rather as part of the sun’s violent magnetic activity and the sunspot cycle (Thomas and Weiss (2008)).

Fig. 14: Plate 14: Sunspots (detail, from Annals Vol. 8)

Fig. 15: Sunspot AR 12665. Photographed August, 2017 (Courtesy NASA/SDO)

In Trouvelot’s age (and still today), scientists used rapidly developing technologies to frequently make barely explicable observations, creating space for new ideas and new explanations of the cosmos. This was encouraged behavior, but within reason: information must be interpreted by as many eyes and voices as possible, debated, and clarified for conclusion before it can speak to universal truths. Eager for such an unprecedented discovery, Trouvelot occasionally succumbed to the excitement of something weird. Inspecting the edge of the solar disk, he saw a large prominence disappear: “the light which rendered it visible abandoned it in an instant.” He lacked the ability to explain this sudden phenomenon, but took his observation as proof of its physical happening. The science community met this unprecedented observation with some skepticism, most notably from E.W. Maunder, who pointed out the technical faults in Trouvelot’s set-up, blaming a potential faulty screw and maligned lens. Maunder allowed for the excitement of witnessing new phenomena, but urged Trouvelot to remember the basic principles of physics, that a body cannot be at once “in a state of rest, of gentle motion, and of rapid motion; the observation must be incorrect, or the interpretation of it.”

Fig. 16: Solar prominence sketches (from “Astronomical sketches taken at Harvard College Observatory”)

Trouvelot was hardly discouraged by such criticism. He enjoyed exploring the curiosities of the universe, and publishing his thoughts for discussion with peers. Besides, this was all secondary to his art. After completing his plates for the Harvard Observatory in 1875, Trouvelot moved to the United States Naval Observatory (USNO) in Washington, DC, which had just installed a new 26-inch refractor telescope. With this, he was able to capture much more detail in the clouds and tendrils of nebulae. While in DC, he also took up field jobs for the U.S. government, including as a cartographer from 1876-7 for the Kentucky Geological survey, and service on a USNO eclipse expedition to Creston, WY in 1878 (Fig. 17).

Fig 17: Total Eclipse of the Sun (from Trouvelot Astronomical Drawings, 1881)

By the end of the 1870s, after ten years of astronomical sketching, Trouvelot wanted to arrange a collection of high quality, large images for lithographic reproduction and distribution. In 1881, with publisher Charles Scribner’s Sons in New York, Trouvelot published 15 images, the highlights of his observational career. Unlike the Harvard plates, which were published in an academic tome for scientists, these lithographs would be poster-sized, to be hung on walls and appreciated as art beyond erudition. Of course, to extend his scientific spirit and best explain the decisions and structures behind his artwork, Trouvelot also published a text, The Trouvelot Astronomical Drawings Manual, that offered simple and approachable explanations of his subjects. The set sold for $125, a pricey sum that only institutions or wealthy collectors could put out. But as large scale, scientifically accurate and justified, and color pictures, these images offered all audiences a new way to engage with and appreciate the cosmos (Fig. 18).

Fig 18: Employees of HCO stage a performance of “The Observatory Pinafore” in front of Trouvelot’s lithograph of Saturn. (Source: Charles Reynes/Tom Fine)

Following this, Trouvelot returned to France. He had been offered the opportunity to work at the Paris Observatory in Meudon, under the prominent astronomer Jules Janssen, who specialized in solar science and sought Trouvelot for his skill at sketching fleeting solar prominences. Janssen desired a daily catalogue, similar to what Trouvelot produced at HCO and through his own hobbying, but something more total and comprehensive: a daily sketchbook of every solar event. Trouvelot did not like this work — he found it lacked “personality” — and so increasingly began experiment with photography. Away from the telescope, he began to test the speed of a camera shutter, in order to most clearly capture a spark of lighting (Fig. 19). His products impressed his peers, but drew the criticism of his supervisor. Overstressed at work, Trouvelot fell ill and died in 1895 (Canales (2009)). According to his son, he was also working on a monograph about Mars before he died (Fig. 20).

Fig. 19: Spark photographs, 1891 (Courtesy Bibliothèque de l’Observatoire de Paris)

Fig. 20: Mars (detail, from Trouvelot Astronomical Drawings, 1881)

Trouvelot’s astronomical artwork offered his contemporaries a new way to engage cosmic imagery with both aesthetic and scientific dimensions. Representing the intricate structures, dynamics, and colors of phenomena gathered from multiple seasons of observation, Trouvelot’s illustrations surpassed the potential of photography at the time to translate the quiet grandeur of space out of the telescope. Come into Wolbach Library to see Trouvelot’s original sketchbooks and plates from the Annals Vol. VIII! And while you’re at the CfA, you might also visit our original of Trouvelot’s lithograph “Group of Sunspots and Veiled Spots,” displayed on the wall on the third floor of the P-building (Fig. 21).

Fig. 21: Group of Sun Spots and Veiled Spots (from Trouvelot Astronomical Drawings, 1881)

To see more of Trouvelot’s artwork, visit these resources:

Harvard College Observatory Annals Vol. 8 (contains color scans of Trouvelot’s plates)

New York Public Library Digital Collections (contains hi-res scans of Trouvelot’s 1881 lithographs)

Heavens Above: Art and Actuality (digital exhibition on Trouvelot from the NYPL, 2001)

Fig. 22: The Planet Jupiter (from Trouvelot Astronomical Drawings, 1881)

Selected Bibliography of Trouvelot’s Writings (in English)

Trouvelot, Étienne Léopold. 1867a. “The American Silk Worm.” The American Naturalist 1 (1):30–38.
———. 1867b. “The American Silk Worm (Concluded).” The American Naturalist 1 (3):145–49.
———. 1867c. “The American Silk Worm (Continued).” The American Naturalist 1 (2):85–94.
———. 1873. “Meteorology of the Future.” Nature 7 (172):283–283.
———. 1875a. “On Some Physical Observations of the Planet Saturn.” Proceedings of the American Academy of Arts and Sciences 11:174–84.
———. 1875b. “On the Veiled Solar Spots.” Proceedings of the American Academy of Arts and Sciences 11:62–69.
———. 1876. “Map of North America: To Illustrate Facts of Geographical Distribution.” [S.l.]: Kentucky Geological Survey.
———. 1877a. “On Saturn’s Rings.” Proceedings of the American Academy of Arts and Sciences 13:191–93.
———. 1877b. “Sudden Extinction of the Light of a Solar Protuberance.” Proceedings of the American Academy of Arts and Sciences 13:187–90.
———. 1877c. “The Moon’s Zodiacal Light.” Proceedings of the American Academy of Arts and Sciences 13:183–84.
———. 1877d. “The Use of the Antennae in Insects.” The American Naturalist 11 (4):193–96.
———. 1877e. “Undulations Observed in the Tail of Coggia’s Comet, 1874.” Proceedings of the American Academy of Arts and Sciences 13:185–86.
———. 1878. “Observations of the Transit of Mercury, May 5-6, 1878;” American Journal of Science and Arts (1820-1879); New Haven 16 (92):124.
———. 1879a. “Observations of Deimos.” Astronomische Nachrichten 94 (2):29–30.
———. 1879b. “Observations of Absorbing Vapours upon the Sun.” Monthly Notices of the Royal Astronomical Society 39 (6):374–79.
———. 1880. “Observations on Jupiter.” Proceedings of the American Academy of Arts and Sciences 16 (May):299–321.
———. 1881a. “Eclipse of the Sun.” Science 2 (30):36–36.
———. 1881b. “Ephemeris of Swift’s Comet.” Science 2 (28):9.
———. 1882. The Trouvelot Astronomical Drawings Manual,. New York: CScribner’s sons.
———. 1884. “The Veiled Solar Spots.” The Observatory 7 (August):228–31.
———. 1886. “On the Protuberances Visible on the Spectrum with a Narrow Slit.” Monthly Notices of the Royal Astronomical Society 46 (6):331–34.
———. 1892. “Fall of a Solar Prominence into the Opening of a Spot.” The Popular Science News and Boston Journal of Chemistry (1883-1895); New York 26 (3):42–43.
Trouvelot, Étienne Léopold, and M. Jameson. 1884. “The Pons-Brooks Comet.” Scientific American (1845-1908); New York, March 22, 1884.
Trouvelot, Étienne Léopold, and Kentucky Geological Survey. 1877. “Preliminary Map: Compiled from Various Surveys.” Boston: AMeisel, lith.

Fig. 23: The Great Nebula in Orion (From the Trouvelot Astronomical Drawings, 1881)

Bibliography on Trouvelot and Sources Cited

Adamo, Angelo. 2016. “Where telescopes cannot (yet) see: the moon as seen by Scriven Bolton, Etienne Trouvelot, Lucien Rudaux, Chesley Bonestell.” April.

Backhus, DeWayne A., and Elizabeth K. Fitch. 2006. “Nineteenth Century E. L. Trouvelot Astronomical Prints at Emporia State University.” Transactions of the Kansas Academy of Science (1903-) 109 (1/2):11–20.

Bendheim, Fred. 2001. “The Art and Science of Etienne Trouvelot.” The Lancet 357 (9272):1983–84.

Canales, Jimena. 2009. A Tenth of a Second: A History. Chicago: University of Chicago Press.

Clark, Stuart. 2007. “Astronomical Fire: Richard Carrington and the Solar Flare of 1859.” Endeavour 31 (3):104–9.

Corbin, B. G. 2007. “Etienne Leopold Trouvelot (1827–1895), the Artist and Astronomer.” In Library and Information Services in Astronomy V, 377:352.

Maunder., E. W. 1886. “Note on M. Trouvelot’s Paper.” Monthly Notices of the Royal Astronomical Society 46 (6):334–35.

NASA Goddard. n.d. Two Weeks in the Life of a Sunspot. Accessed October 12, 2017.

Popova, Maria. 2016. “Étienne Léopold Trouvelot’s Stunning 19th-Century Astronomical Drawings of Celestial Objects and Phenomena.” July 7, 2016.

Rosenfeld, Randall, and William Sheehan. 2011. “How an Artist Brought the Heavens to Earth.” Astronomy; Milwaukee, January 2011.

Silverman, S.M. 2008. “Low-Latitude Auroras: The Great Aurora of 4 February 1872.” Journal of Atmospheric and Solar-Terrestrial Physics 70 (10):1301–8.

Spear, Robert J. 2005. The Great Gypsy Moth War: The History of the First Campaign in Massachusetts to Eradicate the Gypsy Moth, 1890-1901. Amherst: University of Massachusetts Press.

Thomas, John H., and Nigel O. Weiss. 2008. Sunspots and Starspots. Cambridge Astrophysics. Cambridge: Cambridge University Press.

Vázquez, M., and J.M. Vaquero. 2009. The Sun Recorded Through History. Vol. 361. Astrophysics and Space Science Library. New York, NY: Springer New York.

Alex McGrath

Archives Assistant at Wolbach Library
Alex is the Archival Assistant at Wolbach.