University of Pittsburgh | Contact Us  


  Site Map

Press Release: The Parallax Project

Star Search On-line

Pitt's Digital Research Library offers easy access to Allegheny Observatory's historic information
By Edward Galloway

The University of Pittsburgh Library System's Digital Research Library now provides on-line access to historic star data and calculations compiled and published by Pitt's Allegheny Observatory.

More than five decades of the observatory's research-which represents one of the largest systematic, ground-based studies of star distances ever conducted-is now available at the Parallax Project Web site (

Public access to the information previously was limited to a number of deteriorating copies of the Publications of the Allegheny Observatory of the University of Pittsburgh, a 10-volume set published between 1910 and 1969, which primarily documents the observations of the Photographic Parallax Program. Frank Schlesinger, director of the observatory from 1905-1920, established the program to measure a star's distance from the sun (i.e., a parallax) using the photographic record of blue and ultraviolet light emitted by the brightest stars visible from Pittsburgh.

Publications also contains reports on the methodologies of astronomical observation, articles about innovative models of calculating star positions, and descriptions of observational instrumentation.

Schlesinger's program helped put Pittsburgh on the map as a center for high-precision astronometry research and warranted the construction of the 30-inch Thaw Refractor telescope. Built in 1912 almost entirely in Pittsburgh by John A. Brashear, the telescope remains the third-largest refractor in the United States. Parallax information gathered from the Thaw refractor continues to be a fundamental basis for modern-day searches for extra-solar planets.

"It is through the statistical investigation of this data, in comparison to those of other observatories, that our understanding of the intrinsic characteristics of the stars was obtained," said George Gatewood, current director of the observatory. "The data is important in the study of the compilation catalogues to which it contributed, to the weighted mean parallax of modern studies of these stars, and to the understanding of the strengths and limitations of the program, which contributed so profoundly to the determination of the scale of the universe."
The digitization of the data has extended the life of the information and made it more widely available to the research community, including professional and amateur astronomers, high school and college students, and historians of science. The pages of the Publications have been converted into scanned images for viewing so that the on-line material replicates the layout and format of the original volumes.

Users of the digital Publications can also search the content of these volumes for such star identifiers as Allegheny Observatory running number, star name, right ascension, declination, and parallax value. The project also produced two sets of preservation reprints of the Publications to replace the highly acidic and brittle originals.


Back to the Digital Research Library Home Page