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During the five or so years since the advent of the World Wide Web (WWW) the number of servers offering information for astronomers has grown as explosively as that of other servers (cf. [Adorf (1995)]). Perhaps even more than other media, the Internet is flooding us with an excessive amount of information and it has become a challenge to distinguish signal from noise. This report is yet another attempt to do this.

A web address is usually referred to as ``Universal Resource Locator'' (URL), and starts with the characters ``http://''. For better readability I omit these characters here, since one of the most common web browsers (netscape) assumes these by default anyway, unless other strings like ``ftp://'' are specified. All URL links in this overview are given in bold font. It should be emphasized that, owing to the nature of the WWW, some of these URLs may change without notice. The ``File Transfer Protocol'' (FTP) will appear as ftp in this text to coincide with the corresponding Unix command.

A useful introduction to the basics of Internet, explaining electronic mail, telnet, ftp, bulletin boards, ``Netiquette'', Archie, Gopher, Veronica, WAIS can be found e.g. in [Grothkopf (1995)] or [Thomas (1997)]. I shall not repeat these basics here, but rather concentrate on practical tools to obtain astronomical information from the Internet. Many search engines have been developed for browsing WWW servers by keywords, e.g. AltaVista, Lycos, Savvy, Yahoo, WebGlimpse (,,,, donkey.CS.Arizona.EDU/webglimpse, resp.).

Figure 1

Figure 1. A typical example of an astronomer in the Internet age. (Drawing courtesy Georges Paturel)

A comprehensive list of URLs for ``resource discovery'' can be found in [Adorf (1995)], at, or see for some useful tips to define your search adequately. For astronomical topics the flood of URLs returned is smaller at AstroWeb ( or its mirrors (,,,
AstroWeb is a consortium of several astronomers who have been collecting astronomy-relevant links since 1995. However, AstroWeb does not actively skim the web for relevant sites regularly, although it has been done occasionally. It relies mainly on forms sent in by the authors or webmasters of those sites, and currently collects about 2500 links.

Recent reviews related to Internet resources in astronomy were given by Andernach, Hanisch & Murtagh (1994), [Egret & Heck (1995), Murtagh et al. (1995)], Egret & Albrecht (1995), [Ochsenbein & Hearn (1997)], [Heck (1997)], and [Grothkopf et al. (1998)]. Equally useful are the proceedings of the meetings on Astronomical Data Analysis Software and Systems, I-VII, held annually since 1991 and published as ASP Conference Series vols. 25, 52, 61, 77, 101, 125, and 145. For information and electronic proceedings on meetings III-VII, look at:

I do not discuss services explicitly dedicated to amateurs, although there is no well-defined boundary between professional and amateur astronomy, and the latter can be of vital use to professionals, e.g. in the field of variable stars, comets or special solar system events. Indeed, stellar photometry - a field traditionally dominated by amateur observers - boasts a database of variable star observations ( that is the envy of many professionals and a shining example to the professional world of cooperation, organization and service. A further proof of a fruitful interaction between professionals and amateurs is ``The Amateur Sky Survey'' (TASS) which plans to monitor the sky down to 14-16 mag and study variable stars, asteroids and comets (; [Gombert & Droege (1998)]).

A cautionary note: by its very nature of describing ``sites'' on the ``web'', this work is much like a tourist guide with all its imperfections; hotels or restaurants may have closed or changed their chefs, new roads may have been opened, and beaches may have deteriorated or improved. As similar things happen constantly with web pages or URLs, take this work as a suggestion only. You will be the one to adapt it to your own needs, and maintain it as your own reference.

Although I ``visited'' virtually all links quoted in the present report, be prepared to find obsolete, incomplete or no information at all at some URLs. However, after having convinced yourself of missing, obsolete, or incorrect information offered at a given site, do not hesitate to contact the ``webmaster'' or manager of that site and make constructive suggestions for improvement (rather than merely complain). This is even more important if you find a real error in database services used by a wide community. Vice versa, in your own efforts to provide your web pages, try to avoid links to other documents which do not exist or merely claim to be ``under construction'', just imagine the time an interested user with a slow connection may waste in calling such a link.

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