Instrumental changes in astronomy - collection of antique instruments to be cataloged by Adler Planetarium in 1993 - Cover Story

Science News, Dec 19, 1992 by Janet Raloff

Happy to learn of a major, respected local resource, the Websters contacted the planetarium director shortly after they returned home. The good news: He still had all the British Museum's correspondence. The bad news: the Adler lacked the staff to respond to such inquiries. So Rod and Marjorie Webster volunteered.

That was in 1962. And though they were named curators emeriti last year, they continue to commute to Chicago to work with the collection about four days a week.

Rod still has the Martin pocket sundial that kindled their initial interest in the history of astronomy and timekeeping. Over the years, he and Marjorie acquired quite a few other instruments - many of which they have since donated to the Adler - while helping the planetarium strengthen its own collection.

They've also enhanced the Adler's reputation, says William Andrewes, David P. Wheatland curator of the collection of historical scientific instruments at Harvard University. The Adler possesses "an important resource to the history of science and technology in astronomy and navigation," he says. "And Roderick and Marjorie Webster have done a great deal in the last 30 years to build it into one of the premier collections of its kind."

Indeed, adds Owen J. Gingerich, also at Harvard, "anybody who is seriously interested in [antique] instruments knows about Adler. And this is largely because of the efforts of Rod and Madge, who have been indefatigable about visiting other museums and collections and playing a very active role in the [scientific societies]" - avenues through which professionals become aware of important instruments.

And the Adler collection has quite a few, according to Robert Anderson, director of the British Museum. President of the Scientific Instrument Commission of the International Union for the History and Philosophy of Science, he described the Adler's holdings as "the best collection of early astronomical instruments in the whole of the United States and probably the whole continent." Adds Noel M. Swerdlow at the University of Chicago, "Anybody who's working in the study of [early instruments] would want to be using material from this collection."

How? Gingerich has used Adler instruments in documenting forgeries of 17th century astrolabes made by 'Abd al-A'imma. With plates for one or more specific latitudes, these sophisticated planar devices could solve problems involving such things as time, star positions, and length of the day merely by rotating an attached, openwork star map. Many museums had collected ornate brass astrolabes bearing 'Abd al-A'imma's signature and dates that matched the Persian's active period. Gingerich says the astrolabes' delicate calligraphy, "first-class metalworking:' and airy, vine-like filigree seemed to "appeal to curators of art museums." But quite a few museums that didn't understand the science of astrolabes found themselves with nonworking fakes.

By comparing these "degenerates" to true 'Abd al-A'imma astrolabes such as the Adler's, Gingerich was able to identify stylistic differences and errors that characterize the lovely forgeries, probably made early in this century,