Alan McClure

Comet Photographs by Alan McClure

A well known amateur astronomer and comet photographer, Alan McClure was a member of Stony Ridge Observatory for a short time, serving on the SRO Executive Committee as an Expediter during the planning and construction phases between 1957 and 1959.

Alan's comet photography has been widely published in scientific papers and texts, and on magazine covers (Sky & Telescope). A number of his photographs were also published in the classic Burnham's Celestial Handbook.

<- This photo of Comet Arend-Roland was taken by Alan McClure on April 24, 1957 and presented to the members of SRO at a meeting the next night. This image clearly shows the rare anti-tail, or sun-pointing tail feature of this comet. Anti-tails have been produced by only a few comets in history, some being C/Arend-Roland (1957), C/Hale-Bopp (1995), C/Kohoutek (1973). The anti-tail is not actually pointing toward the Sun, but is a projection effect of dust in the comet's orbital path. The dust in the path behind the comet becomes visible when the comet's orbit lies in the same plane as the Earth's.

Comet Mrkos (above) was photographed by Alan McClure on August 13, 1957 (apparently a great year for comets). This picture clearly shows two types of cometary tails, the straight ion tail, and the curved dust tail. Both tails point away from the Sun. The straight ion tail is formed from charged particles that are highly accelerated by the Sun's solar wind. The curved trail is caused by dust-sized particles being blown off the surface of the comet by the radiation pressure of sunlight. Comet Mrkos's orbit did not lie in the plan of Earth's orbit, so an anti-tail, as seen from C/Arend-Roland was not present.

This photo of Alan McClure's astro-photography setup is courtesy of SRO member John E. Rogers who obtained it from an auction of Alan's estate. Note the George Carroll mount used by Alan.