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Published online 6 February 2009 | Nature | doi:10.1038/news.2009.81
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The world's top ten telescopes revealed
The best observatories ranked by their scientific impact.
It doesn't take a big mirror to have a big impact. The Sloan Digital Sky Survey, a project conducted with a modest 2.
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This article reveals some of the dangers of performing bibliometric studies. The astro-ph paper by Madrid, J. P. & Macchetto, F. D. uses an extremely narrow approach to identifying the top ten telescopes. While bibliometric studies are an important tool in measuring the performance of a telescope, and to compare performance across telescopes, they can easily be misused. There are several weaknesses and limitations in the type of bibliometric study reported in this article. First, the productivity of a general use telescope slowly increases once it comes online. It can take up to 10 years before such a telescope reaches its full paper producing capacity. As a telescope?s production is ramping up it is less likely to have papers in the ?top 200? of a given year (a telescope?s chances double if it produces twice as many papers). There is also the fact that there are two Keck telescopes and four VLTs, which will also increase the chance that their papers will appear in the top 200 cited papers of a given year. Second, one must be careful not to compare ?apples and oranges?. Survey telescopes such as Sloan are designed to produce huge databases that will be analyzed to not only produce papers, but to generate target lists for further observations. These survey telescopes and/or programs are similar to an atomic line list or a list of photometric standards. They provide fundamental data that is used in a countless number of ways in other astronomical research. Such a narrow metric, as used in this paper, is of little use in comparing the performance of telescopes. Using a single metric as the mean or median citations per paper, or the number of papers in the top 200 cited papers, does not capture the true performance of a telescope. A more sophisticated analysis which looks at the distribution of the impact of the research, factors in the age of the telescopes and takes into account the type of research performed by each telescope is needed to for a fair comparison. Understanding the productivity and impact of an observatory is a complex undertaking. Simplified approaches such as the one reported on in this article give a narrow and somewhat misleading glimpse into the impact of research performed by various telescopes.