This a large, 5° objective prism for an astronomical spectrograph. The objective prism is in its storage mount, which is a crude wooden frame held with screws and nails. The mount is marked, "~5° PRISM." A hang tag, which is partly torn, reads, "Property / of / Rev. J. H. Metc[alf]."

There is a piece of cardstock placed between the glass prism and the wood frame. The cardstock has a circular aperture marked in pencil, which is cut away inside the pencil line. Two long screws protrude from the front and back of the frame. The edges of the prism are beveled.

In Collection(s)

Exhibit 2005--CHSI's Putnam Gallery

Signedhang tag: Property / of / Rev. J. H. Metc[alf]

Inscribedon mount: ~5° PRISM

FunctionThe objective prism would be mounted in a cell at the end of a large telescope in front of the objective lens. Starlight passing through the prism is dispersed into its spectral lines. These are usually photographed at the other end of the tube.

Historical AttributesThe Reverend Joel Hastings Metcalf was a Unitarian minister in Taunton, Massachusetts, who was a well-known and highly regarded amateur astronomer at the turn of the century. He was on friendly terms with astronomers at Harvard. He was especially known for discovering numerous asteroids, comets, and variable stars.

Joel Hastings Metcalf made this objective prism, and it was used at Harvard's Oak Ridge Observatory, located in Harvard, Massachusetts.

ProvenanceJoel Hastings Metcalf; Harvard College Observatory; George R. Agassiz Station, Harvard, MA; transfer to CHSI in 2005.