"We have loved the stars too fondly to be fearful of the night."

John Brashear

About the Parallax Project

In March 2001 the Digital Research Library (DRL) at the University Library System commenced the Parallax Project by gathering and preparing the Publications of the Allegheny Observatory of the University of Pittsburgh for digitization and display on the Web. The DRL scanned the 10 volumes, created two sets of facsimile reprints to replace the originals, and entered selective star data into a database to enable searching by a variety of access points.

The digital version of the Publications can be searched or browsed. The pages of the Publications have been converted into scanned images for viewing so that the online material will replicate the original layout and format of the published material.

With recommendations by the Allegheny Observatory, the Digital Research Library extracted specific star information from the volumes to facilitate search and retrieval. During the first stage of this process, staff recorded the following information for each star (if known):

• Allegheny Observatory number
• Star name
• Right ascension
• Declination
• B.D. number
• Parallax value
• Parallax error
• Henry Draper number

During the second stage of the data-gathering process, staff recorded the "instance" of each star (i.e., on what page(s) of a volume(s) the star was cited) and assigned a specific study type to the star: Light curve, Orbit, Radial velocity, Relative parallax, Spectroscopic binary, or Other. The subsequent recording of this information in electronic format gives users powerful search capability within the Publications, and supplies important contextual information about the stars.

The digitization of the Publications and the subsequent production of facsimile reprints will ensure that this historic and valuable material will continue to be made available to the research community. The Publications held by the University of Pittsburgh are in very bad physical condition: the paper is acidic, brittle and yellowing; many volumes show signs of foxing (i.e., brown stains, specks, spots, or blotches found on paper that is aging); and the spines are detached from several volumes. In this deteriorated condition continuing to use the Publications will actually harm them. The digital and facsimile versions of the Publications by the DRL will allow the 59 years of information gathered by University of Pittsburgh researchers at the Allegheny Observatory to continue to contribute to worldwide understanding of the universe.

The Parallax Project extends the life of the Publications and more broadly disseminates the information to researchers around the world as it continues to be of significant interest to scientists, professional and amateur astronomers, faculty and college students, and historians of science.

Research Value

Professional astronomers who are searching for planets circling other stars will find the parallax data most useful. Their methods of detection all center around comparing precise positions of stars at various time intervals to see whether they show evidence of gravitational interaction with large bodies that are very close to them.  The method has been refined to the point where careful observation can distinguish between brown dwarf stars, white dwarf stars, and planets of various sizes.  The orbits of these objects can be calculated.  The more extensive the historical record of the position of the star in consideration, the more precise the calculation of the star's orbital parameter, or "wobble," can be.  The enhanced precision allows for improved resolution of orbits, and improved determination of the nature of the circling object.  As an example of the current utility of these records, one can go to the website of Kitt Peak National Observatory in Tucson, Arizona.  This site contains a bibliography of 44,000 references from 25 key journals and other sources listing information about radial velocities of stars.  The Publications are on the short list of titles considered to contain crucial and reliable data.

Historians of science, photography, and technology will also be interested in the Publications.  For example, an article from the Publications is listed on a bibliography of crucial papers in the history of photography, astrometry, and photometry. One of the key sources is an article written by Frank Schlesinger, a former director of the Allegheny Observatory, on "A Description of the first Gaertner Measuring Engine."  A more extensive use of material from the Allegheny Observatory is by Michael Hoskin of Churchill College, Cambridge in the United Kingdom.  His article, "The Value of Archives in Writing the History of Astronomy" makes use of material from the Allegheny Observatory.  He discusses the importance of both the printed record and of the primary material that is crucial to historians--letters, diaries, and observational notebooks.

The large community of local and national amateur astronomers will also find a value in the Parallax Project website.  The Amateur Astronomy Association of Pittsburgh (AAAP) website illustrates the seriousness and depth with which amateur astronomers take their vocation and the high level of scientific rigor which some of them may use in pursuing their hobby or vocation.  A similar website exists for the American Association of Amateur Astronomers (AAAA).  The AAAA website includes information for children: Hands On Universe, Astronomy For Kids (described as astronomy for and by kids), Star Child, Imagine the Universe, and Windows on the Universe.  The older students and the adult amateurs would potentially find use for the parallax star data in doing projects to illustrate how planets circling other stars are found.