Computer Databases

Before discussing computer star charts it worth looking at the raw data itself. Most computer star charting programs use the raw data from the Washington Double Star Catalogue, or WDS for short. This database which is updated daily with new measures and recently discovered double stars is maintained by the United States naval Observatory and is available through the Internet at http://ad.usno.

navy.mil/wds/wds.html. This site includes the database itself which can be downloaded, although at the time of writing (October 2002) it was 11.5 Mb, along with information on the structure of the catalogue and a method of querying it. In order to help get information into a form useful for amateurs to study several people have written access programs to this data. Most of these databases are based on the 1996 release of the catalogue which was the last sent out on CD-ROM. Probably the best is a program put out by the hardworking group at the Saguaro Astronomy group in Arizona. They have generated a double star program similar to their better known SAC database for deep-sky objects called SAC DB 2.1 which was an attempt to provide a working list of double stars for owners of modest telescopes.

The database was based on a version of the WDS from 1991 and took double stars with primaries whose magnitudes were greater than magnitude 9 and secondaries whose magnitudes were greater than 13. They then wrote a small database program which allows the user to query the database based on constellation, magnitude or just by star designation and get information on that star. A typical screen from that program is shown in Figure 23.1. The program is available for free from their website at www.saguaroastro.org. It is still a DOS type utility. As double stars became of more interest several other utilities became available which allowed the user to either input data or take data from

Figure 23.1. An example from the Saguaro database

Figure 23.1. An example from the Saguaro database

Figure 23.2. An example of the software by Brian Workman.

the orbital catalogues and generate positions or orbits based on current data.

The example shown in Figure 23.2 is the data taken from a useful Excel spreadsheet by Brian Workman available via http://www.psiaz.com/polakis/index.html. Another useful site is Richard Dibon-Smith's orbital pages at http://www.dibonsmith.com/orbits.htm. For raw data on double stars the data from the Hipparcos mission has been made available on a CD called Celestia 2000 which is available from Sky Publishing in North America or from ESA for the rest of the world. This CD allows you to search on the Hipparcos catalogue for double star data and provide a rudimentary plot of this data. The plotting functionality is not as great as the mainstream programs but the data is some of the more accurate positional data for the brighter stars that Hipparcos measured.

Figure 23.2. An example of the software by Brian Workman.

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