So you've bought a PC and modem and registered with an Internet Service Provider. But how do you find sites on the World Wide Web which relate to variable stars ?
One way is to start from a web site for which you know the address - for
example, the BAA VSS site, whose address is :
http://www.telf-ast.demon.co.uk/index.html. This site includes links to a number of other web sites which relate to variable stars, such as the AAVSO site and the SPA VSS site. From these other sites, you can follow links to other variable star sites,and so on ....
Such a method will hopefully lead you to the most interesting sites. However, it could take a long time to find a site which has few links pointing to it, and there's always the risk of going around in circles. Is there a quicker way to find more sites?
The best solution is to use a "search engine". There are many of these available. All you have to do is type in a phrase for which you wish to search, and the search engine will then look for matches in its database of web site contents and list the matches that it finds.
Below are the number of matches found in some recent searches using four search engines:
|Search for||Alta Vista||Yahoo||Lycos||Infoseek|
|"variable star section"||114||114||52||69|
The above totals are not totals for the whole web - no search engine searches the whole web. The totals for Yahoo and Alta Vista are the same in some cases because, after performing an "intelligent search",Yahoo will, if no matches have been found, fall back on an Alta Vista search. In general, sites will be listed in an order such that the "best"matches come first. Some search engines, such as Infoseek, give a rating as to how good a match each site is. Alta Vista identifies the language in which each site is written - curiously rather a lot of the matches for "omicron ceti" are in Swedish.
Different search engines use different criteria to decide on which are the best matches. For example, when searching for "variable starsection" using Alta Vista, a SPA VSS page is the 1st match whereas the BAA VSS pages don't appear until the 21st match (which happens to be a link to an article about the SPA Variable Star Section).However, the BAA VSS pages appear ahead of the SPA VSS pages when using Lycos (4th) and Infoseek (11th).
Some searches, such as Infoseek, try to avoid "duplication" in their matches, others don't. For example, 7 out of the first 10 matches listed for "variable star section" by Alta Vista are for individual pages within the SPA VSS site
Bear in mind that not all sites found will be relevant to astronomy - matches for "mira" include fan clubs for the actress Mira Furlan ("Delenn" in Babylon 5), matches for "omicron ceti" included descriptions of some Star Trek episodes in which the USS Enterprise visited the Omicron Ceti system (but forgot to make any brightness estimates), and matches for "algol" include sites about algol programming languages.
Yahoo's "intelligent" search is not always intelligent - none of the 8 matches listed by Yahoo for "algol" refer to the star algol !
Obviously, the more precise you are in your search criteria the more likely it is (usually) that the sites found will contain genuine references to what you have searched for. As seen above, if you want to find pages about Nova Cas 1993 (V705 Cas), searching for "novacas" will get you to the relevant web pages quicker than will searching for just "nova". However, there was also a Nova Cas 1995and whereas Alta Vista found 134 matches for "nova cas", it found just 36 for "nova cas 1993", 4 for "nova cas 93" and 71 for "v705cas".
The above searches have been fairly basic. Most search engines allow more sophisticated searches such as searching for sites which contain "algol" but not "language", or which contain both "mira" and "omicron". In this way, spurious matches can be minimised.
Search engine links : Alta Vista | Infoseek | Lycos | Yahoo