1. 5-inch doublet, forming, with lens 213d (now missing), the elements of a quadruplet, used with the 1922 Lick Einstein camera.

2. Detail showing postage-stamp spacers.

Accession card.
Item Name  5-inch McDowell doublet lenses (only C present)
Catalog No.  SO000213
Category  Lenses and Mirrors : Lenses : Regular (C1a)
Description  An air-spaced doublet lens, designed by Professor Hastings of Yale University, and made by Jimmy McDowell of Brashear Co. for Lick Observatory in 1922. The lens is mounted in a brass cell of approx. 6-inch diameter x 2 inches high; the elements show the Brashear's characteristic postage-stamp spacers.

Two identical pairs were made (212A & B, and 213 C & D) of which D has been missing since 1938. A, B, and C are present in the collection. Each pair forms a four-element lens of 15-foot focal length when mounted in the brass barrels SO000212 and SO000213. The present lens is the front doublet of barrel 213.

The 15-foot camera, along with the 5-foot camera (see SO001005 and SO001006), was designed to test General Relativity by producing wide-field images centered on the eclipsed sun, from which the apparent positions of the stars could be measured to look for Relativity's predicted deflection. (Also used at1932 Fryeburg, Maine eclipse to photograph the corona).

EcBk, Wallal, 1922
EcBk, Fryeburg, 1932

References  Campbell, W. W. 1922. The Total Eclipse of September 21, 1922. Journal of the Royal Astronomical Society of Canada 16:186-190.

Campbell, W. W. 1923. The Total Eclipse of the Sun, September 21, 1922. Publications of the Astronomical Society of the Pacific 35 (203):11-44.

Campbell, W. W. and R. Trumpler. 1923. Observations on the Deflection of Light in Passing Through the Sun's Gravitational Field, Made During the Total Solar Eclipse of September 21, 1923. Publications of the Astronomical Society of the Pacific 35:158-163.

Moore, J. H. 1932. Crocker Eclipse Expedition to Fryeburg, Maine: The Lick Observatory. Publications of the Astronomical Society of the Pacific 44 (261):341-352.