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Lens Assembly for Einstein Camera


This item is a cylindrical lens assembly contained in a wooden shipping crate with black writing on the lid. The lid lifts off revealing the lens assembly.

The lens is supported inside the box by semi-circular sections of wooden padded with dark blue felt. Sections of this are fitted underneath and four pieces fit over the top and can be lifted out to remove the lens. The lens ends are supported underneath by crumpled newspaper and heavy black paper. The newspaper dates to April 3, 1929 and includes the front page of the Toronto Daily Star. There is earth and other organic detritus in the bottom of the crate.

The lens assembly consists of two 6″ lenses mounted at either end of a metal tube (barrel) with covers on either ends. Each lens is set in a brass ring and removable by unscrewing it from the barrel. There is nothing else inside the tube. There is a heavy connection section in the middle of the exterior of the tube, with large threads visible around the circumference.

Each end of the lens consists of a pair of lenses set closely together, making four lenses in total. Each pair (doublet) of lenses are spaced by small pieces of red and white paper–postage stamps–visible around the rim of the lens.

Accession Number: 2019.ast.241

Alternative Name:

Primary Materials:

Wood, Glass, Metal: Iron Alloy, Metal: Copper Alloy, Paper


Painted or burned on the wooden lid: “No. 16
Ship to University of Toronto

Engraved on the box edge and matching removable interior semi-circular sections: “I” “II” “III” “IV”

Engraved on the rim of one of the lenses: “FRONT”

Dimensions (cm):

Box: Length = 64, Width = 29, Height = 32


This is a quadruplet camera lens with an aperture of 6 inches and a focus length of 11 feet. It was constructed for an “Einstein Camera” used by University of Toronto professor C.A. Chant and Dominion Astrophysical Observatory astronomer R.K Young during an scientific expedition to the total solar eclipse in Australia September 21, 1922 . It was used to take large scale photos during the eclipse’s totality to compare against plates of the same patch of sky and measure the deflection of starlight around the sun to test the predictions of Albert Einstein’s General Theory of Relativity. Images were successfully made during the 1922 eclipse. A modified camera using the lens was used again by Chant and others from the Toronto Department of Astronomy for a similar purpose in 1932, at an eclipse expedition in Quebec; however, no images were secured in 1932 as it was cloudy.


Very Good: The shipping crate is intact, but very dirty on the ends, and scratched across its surface. There is a burn mark on one side of the box. There is a large notch in the side of the box.

The barrel of the lens and the lens covers are scratched, with the paint on the lens covers chipping. The lenses are in excellent condition, with no apparent damage to the glass, and the rims with only small scratches.

Associated Instruments:


Lenses: J.B. McDowell, John A. Brashear Co., Pittsburgh

Crate: Consolidated Optical Co., Toronto; or, University of Toronto

It is not clear if the metal tube component of the lens and/or the lens covers were made by Brashear or by Consolidated Optical Co.

Date of Manufacture: Spring 1922


This artifact was kept at the David Dunlap Observatory likely from its opening in 1935 until 2009. Upon the sale of the Observatory in that year, it was moved to the University of Toronto’s Department of Astronomy & Astrophysics at the St George Campus. In 2017 it was moved to a new storage location in the McLennan Physical Laboratories.

Additional Information and References:

This lens was ordered from the John A. Brashear Co. by Clarence A. Chant, Professor of Astronomy at the University of Toronto in the spring of 1922 expressly for the eclipse expedition to test Einstein’s General Theory of Relativity. This had been attempted at a previous eclipse in 1919 by Arthur Eddington, but whose results were not considered definitive and the 1922 eclipse, falling over Australia, represented the next best option for capturing images. An article by Chant and R.K. Young who also joined the trip from the Dominion Astrophysical Observatory in Victoria, B.C. describes the construction of the camera and lens:

“In the spring of 1921 Mr. Chant obtained permission from the President of the University of Toronto to order a photographic lens of aperture six inches and focal length eleven feet, which he hoped he would be able to use for testing the Einstein theory at the eclipse of September 1922. Knowing that Director Campbell of the Lick Observatory, intended to observe this eclipse… Mr. Chant kept in communication with him, but it was not until November that it was learned that the Australian Government would provide facilities for taking the parties from the United States and Canada to the desired point.

Meanwhile plans for the camera were drawn, but a grant for its construction was not available until January, 1922. The work was at once begun, and many difficulties were encountered, one being a strike in the engineering trades in England, which prevented the delivery of a suitable driving clock.

The lens of the camera was of the symmetrical four-element type and was made by McDowell of Pittsburgh. Its aperture was 6 inches and focal length 11 feet. The “tube” of the camera was of open iron work, the cross-section being 13 inches square and the length being, of course, 11 feet. The corner strips were of angle-iron 1/4-inch thick, and the sides of the tube were made rigid and strong by iron braces 1/4-inch thick and 1 1/12 inch wide, which were riveted to the angle-iron. It was covered first with heavy farmer’s satin and then with rubber sheeting. One end of the tube was covered by an iron plate bearing the collar into which the lens screwed. This collar could be adjusted in order to collimate the lens. The camera back was made from aluminium. It was carried on the ends of four steel rods which moved in holes in metal blocks, brazed within the tube to the angle-iron corners, for the purpose of focussing the image on the plate. The back could be clamped in any position and a steel scale allowed one to record the position of the back. The plate holders were of aluminium and were made with great care, so that in each case the film of the photographic plate should be at the same distance from the lens.

On two opposite sides of the camera tube, and about mid-way in its length, iron plates 1/4-inch thick and 13 inches square were riveted, and at the middle of each of these there was bolted a half of a flange coupling, bored out to take the steel declination axis 1 3/16 inches in diameter.

The tube was designed and the working drawings for it were made by C.R. Young, B.A.Sc., C.E., Professor of Applied Mechanics in the University of Toronto. The camera, including the plate-holders, was made in Toronto by the Consolidated Optical Co.” (pgs 275-276)

Chant and Young’s article goes onto describe in detail the process of capturing images in preparation for and during the eclipse, and the processing and analysis of the photographs captured, and the results. These results were positive but broadly inconclusive: “Considering the small number of stars the agreement with the amount predicted by Einstein is surprisingly good. They are not of sufficiency accuracy to say what law it follows, but they are, however, in harmony with the amount predicted.” (pg 284)

By 1922, the creator of the lens, J.B. “Jimmy” McDowell, (1860-1924), employed by the John A. Brashear Co. in Pittsburgh, had made high quality lenses for numerous instruments and observatories across North America. He was considered by J.S. Plaskett, then-director of the Dominion Astrophysical Observatory in Victoria B.C. but himself a mechanic of considerable experience, to be the “real optician” of the Brashear company, and described his admiration for his exacting work and skill.

“…[E]ven Dr. Brashear was not more scrupulous or particular about quality than Mr. McDowell.. He was always ready to try any experiments promising improvement in optical performance and always loath to make any charge for such experimental work.” (pg 187)

The small red and white paper spaces between each pair of lenses, postage stamps (visible here), were a signature characteristic of Brashear Co. lenses.

More discussion of the eclipse expedition by W.W. Campbell, the director of the Lick Observatory, can be found in “The Total Eclipse of the Sun, September 21, 1922“. Campbell describes how previous attempts to test Einstein’s theory had been thwarted by the onset of World War One, discusses the instrumentation, describes the difficulties of travel to and across Australia with equipment, and comments about other complications and successes in the capturing, developing and analysis of the plates. The Lick expedition also involved a pair of cameras very similar to the Toronto one, also made by McDowell, although with five rather than six inch lenses. The complete lens assembly of one and one of the doublet lenses and barrel of the other survive at the Lick Observatory. Identical postage stamp spacers identifying the work as Brashear are visible in the Lick photographs of the second camera lens.

The lens seems to appear in an image among those taken by the Lick Observatory team, available in the Digital Collections of the UC Santa Cruz University Library (collection call number UA 36). The image depicts two astronomers with an instrument identified as a “heliograph” (i.e. a camera for the photography of the sun). The lens and cover depicted matches the U of T lens, and not the Lick lens, which has a brass tube. The clothing of the individuals depicted exactly matches the clothes of R.K. Young (left) and C.A. Chant (right) seen in another photo also in the collection, as does the mottled white-and-dark surface of the telescopic sight attached on the left hand side of the camera.


Campbell, W.W. “The Total Eclipse of the Sun, September 21, 1922Publications of the Astronomical Society of the Pacific, Vol. 35, No. 203 (1923): 11-44

Chant, C.A., Young, R.K. “Evidence of the Bending of the Rays of Light on Passing the Sun, Obtained by the Canadian Expedition to Observe the Australian EclipsePublications of the Dominion Astrophysical Observatory, Victoria, Vol.. II, No. 15 (1923): 275-285.

Plaskett, J.S., “James B. McDowell: An appreciationJournal of the Royal Astronomical Society of Canada Vol. 18 (1924): 185-193

Historical Notes: