Southern Hemisphere

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In 1899 at the Royal Observatory at the Cape of Good Hope, R.T.A. Innes published A Reference Catalogue of

Figure 24.1. Julie Nicholas, formerly Librarian at the Institute of Astronomy, with copies of Struves' first catalogue, the IDS (open on the desk), and the WDS (on CD-ROM). The latter could also contain every measure ever made. (R.Sword (IOA))

Southern Double Stars, but chose rather narrow limits to decide which pairs went in. In 1903 Innes became Government Astronomer at the Union Observatory Johannesburg and in 1925, ably assisted by W.H. van den Bos and W.S. Finsen, started on a new survey for double stars in the southern skies using the newly installed 26.5-inch (67-cm) Grubb refractor. Innes compiled the Southern Double Star Catalogue in 1927 as a means of identifying new double stars during the subsequent searches. This covered the zones -90° to -19° and contained 7041 systems.

In 1910 R.P. Lamont a wealthy industrialist and friend of the double star observer W.J. Hussey (who was latterly Director of the Observatory of the University of Michigan) had authorised plans for a large telescope for double star observation. Hussey planned to install it at Bloemfontein in South Africa to continue his own searches for new double stars. Tragically Hussey died in 1926 en route to South Africa but the project was taken over by R.A. Rossiter who stayed until 1952. Rossiter then compiled the Catalogue of Southern Double Stars, essentially a list of the pairs discovered by Rossiter and his assistants Donner and Jessup (Figure 24.2) - more than 7600 in the 24 years ending 1952.

Figure 24.1. Julie Nicholas, formerly Librarian at the Institute of Astronomy, with copies of Struves' first catalogue, the IDS (open on the desk), and the WDS (on CD-ROM). The latter could also contain every measure ever made. (R.Sword (IOA))

Figure 24.2. These 5 observers were responsible for more than 10,000 double star discoveries. Pictured outside the Lamont-Hussey Observatory in September 1928 are (left to right) H.F.Donner, W.S.Finsen, R.A.Rossiter, W.H.van den Bos and M.K.Jessup.

All-Sky Catalogues

The first all-sky catalogue of double stars did not appear until 1961. It is printed in two volumes as Volume 21 of the Publications of Lick Observatory and its formal title is Index Catalogue of Visual Double Stars 1961.0. It is still the only printed version of an all encompassing catalogue and is now likely to remain so given that it runs to 1400 pages of closely printed script. Edited by Hamilton Jeffers, Willem van den Bos and Frances Greeby, the Index Catalogue of Double Stars or IDS was issued to include the large number of discoveries that had been made at the Republic and Lamont-Hussey Observatories in South Africa (Figure 24.3).

With the development of the Hipparcos project in the 1970s it was apparent that with the very approximate positions (0.1 minutes of time in RA and 1-2' in Declination) and insufficient cross references between the IDS and other catalogues - largely the Durchmusterungs - it would be a disadvantage when programming the satellite to observe double and multiple systems. This led Jean Dommanget, a member of the INCS (Input Catalogue) consortium and a well-known double star researcher at the Royal Observatory in Brussels to propose a new catalogue - the CCDM (Catalogue of the Components of Double and Multiple Stars) which would feature considerably better

W.H. van den Bos looks on proudly as the President of the South African Council for Scientific and Industrial Research, Dr. S. Meiring Naude, peruses a copy of the IDS (1968) (copyright CSIR).

W.H. van den Bos looks on proudly as the President of the South African Council for Scientific and Industrial Research, Dr. S. Meiring Naude, peruses a copy of the IDS (1968) (copyright CSIR).

positions and photometry for the stars in the Hipparcos input catalogue (about 120,000) which were known to be double or multiple. More importantly it was necessary to list all the components of each system so that the new discoveries made by Hipparcos could be evaluated more easily. The purpose of the CCDM is to be complementary to the WDS. It does not aim to be all-inclusive but it does contain more detailed information on a smaller number of systems. In collaboration with Omer Nys, Jean Dommanget produced the first version of CCDM in 1994 and a second version appeared in 2002 which contains 49,325 systems.

The current version of CCDM can be found via the CDS at Strasbourg at http://cdsweb.u-strasbg.fr/cgi-bin/Cat?I/269A and a file of all the systems observed by the Hipparcos satellite which is essentially a subset of the CCDM can be found at http://cdsweb.u-strasbg.fr/cgi-bin/Cat?I/260

The central data repository for visual double star data continues to be kept at the United States Naval Observatory. In the early 1960s the late Charles Worley received the Index Catalogue (in card form) from Lick Observatory which had appeared in two parts as described above. Copies of this catalogue were rarely seen except in the reference libraries of observatories so data on visual double stars was not easy to obtain at this time.

Worley (Figure 24.4), ably assisted by Geoffrey G. Douglass and others, spent the rest of his working career bringing the Lick Catalogue up-to-date. This

Figure 24.4. Charles Worley, pictured at Santiago de Compostela, in July 1996. (Angela Argyle)

meant, amongst other tasks, converting the punch cards into computer files, inputting new measures and discoveries on a regular basis and weeding out errors. The result of this was the first electronic version of the Washington Double Star Catalogue, WDS 1996.0 - so called because it represented the state of the data archive at the beginning of 1996. It had grown to some 78,000 entries so producing a printed copy was out of the question. After Worley's death the archive was taken over by Dr. Brian D. Mason who had done his research in the discipline of speckle interferometry at Georgia State University. Dr. Mason and his team have recently produced the WDS 2001.0 and are issuing incremental updates at regular intervals. The current catalogue contains the new pairs discovered by the Hipparcos satellite and so offers double star observers a whole new set of pairs to measure. Most of these pairs have remained unobserved from the ground but it must be noted that many are very difficult and require both large apertures and good seeing.

The USNO have recently produced a CD-ROM which contains, amongst other useful files, the WDS 2001.0 catalogue. This is the version of the WDS frozen as of

Figure 24.4. Charles Worley, pictured at Santiago de Compostela, in July 1996. (Angela Argyle)

late Sept 2001 and contains a single-line entry for each of 84,486 systems. The updated version of the WDS catalogue can be downloaded from the USNO site at http://ad.usno.navy.mil/ad/wds/wds.html and is currently 11.5 MByte in size (98,084 systems). It is also available in portions of 6 hour intervals in RA. Another file contains useful notes on systems of interest. In addition there are two useful cross-reference files, for Hipparcos v HDS numbers (Hipparcos Double Stars) and WDS v ADS. Although the latter reference number is not adopted in the current WDS, it is still used by orbit-computers. The data is given in a rather compact form and so on first acquaintance it needs the use of the accompanying key to decipher what the data columns mean. The main advantage of the online WDS is that it is not only obtainable by anyone (try finding a copy of the IDS!) but it is a dynamic database and is updated regularly!

For those not on the Internet then the enclosed CD-ROM contains a recent edition of the on-line WDS catalogue together with the Sixth Orbit Catalogue and the Fourth Interferometric Catalogue.

Whilst the WDS catalogue is large, it is dwarfed by the Observations Catalogue which is also maintained by USNO but which is not generally accessible. At the time of writing (September 2002) this consisted of 585,261 mean observations of 98,084 pairs. Requests for data can be made using the request form on the website. This is particularly useful for orbit determinations for instance.

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