In 1965 Charles arranged for the database of double star data, the Index Catalogue of Visual Double Stars (IDS), to be transferred from the Lick Observatory to the USNO. This database has become a truly comprehensive resource under his guidance, and is formally recognized as the international source of double star data by the International Astronomical Union (IAU). He updated the database on a continuing basis adding 290,400 observational records to the original 179,000 and increasing the original 64,000 systems by an additional 17,100 through careful literature searches and extensive communication with other double star observers throughout the world. During the past three years he extended the scope and utility of the database, now known as the Washington Double Star Catalog (WDS) by adding accurate photometric data, improved spectral types, and identification information. The project was completed in 1996, and the revised WDS is available on the world wide web. Most recently he oversaw the addition of 15,000 Hipparcos Catalog double stars into the WDS. Requests for information from the WDS database arrive daily from astronomers all over the world.
In collaboration with William Finsen and later Wulff Heintz, Charles produced two Catalogs of Orbits of Visual Binary Stars, the most recent published in 1983. At the time of his death he was preparing what would have been a new version.
In recent years an accurate knowledge of double and multiple star separations, position angles, and orbital motions has become increasingly important to astronomy. It is now realized that not only must double stars be identified and calibrated in order to produce the best astrometric catalogs of stellar positions, but also the varying centers of emission at different wavelength bands must be taken into account to meet modern high-precision astrometric needs. For Charles's contribution to this aspect of astrometry, he received the 1994 U.S. Naval Observatory Simon Newcomb Award for Scientific Research Achievement.
In 1991 he was elected as vice-president of Commission 26 of the IAU (Multiple & Double Stars) and became president of that commission at the IAU General Assembly in 1994. He was a member of IAU Commission 5, the American Astronomical Society, including the AAS Historical Astronomy Division, and the Royal Astronomical Society. He was also an active supporter of the amateur community, and published a series of articles in Sky and Telescope and produced the double star section of the "Observer's Handbook".
During his career Charles made over 40,000 measures of double and multiple stars using the USNO filar micrometer on telescopes in the northern and southern hemispheres. In 1990 he obtained a speckle interferometer in order to improve the accuracy of double star measurements. During the past seven years he oversaw improvements in both instrumentation and software implementation that resulted in making the USNO the world's second largest producer of double star observations using a speckle interferometer. Under Charles's direction more than 9,200 observations were made with the speckle interferometer on 1,100 systems down to separations of one-fifth of an arcsecond, the theoretical limit of the 26-inch refractor. Recently the speckle interferometer has been used to observe Hipparcos problem stars on the McDonald 2.1-m Otto Struve telescope. His special interest in nearby stars led to the discovery of 39 new, cool stellar companions. These companions which are faint and difficult to observe provide critical census information on the solar neighborhood. From 1954 to 1997 he published some 75 professional papers primarily on double star astronomy and gave numerous invited presentations at meetings. He was known for exacting standards and high quality best typified by his paper challenging all other double star observers; "Is This Orbit Really Necessary?"
We are reminded of a favorite quote of Charles' from Paul Couteau's book "Observing Visual Double Stars":
"Do not forget that an astronomer who observes perfect images visually is a wild beast who devours his prey. Do not disturb him under any pretext. Let nature take its course".
Charles will be sorely missed by his many friends and colleagues.
Geoffrey G. Douglass
Thomas E. Corbin
Brian D. Mason
U. S. Naval Observatory