Talk:Carte du Ciel

Astrographic Catalogue

The vast amount of work invested in the Astrographic Catalogue, taking plates, measuring, and publishing, looked for a long time as giving only little scientific profit. But today we are very much indebted to this great effort. The data were brought from the printed books onto machine readable form in the 1990ies. The data were then reduced anew with the reference stars from the Hipparcos astrometry satellite, especially with the 2.5 million stars in the Tycho-2 Catalogue. The proper motions of all these stars could then be derived especially thanks to the Astrographic Catalogue, but star positions from more than 140 other ground-based catalogues were also used. The resulting Tycho-2 Catalogue is the present best, most accurate and most complete, star catalogue of the brightest stars on the sky. It is the basis for deriving positions for all fainter stars on the sky.

The present text in Wikipedia on this subject should be revised accordingly. I have done that already!

Best regards Erik Høg

Thanks for your effort, but writing your name in the article itself is not really in accordance with the Wikipedia policy as I understand it, so I will remove your name from the article only (but not from the current discussion page). I notice that the change was done without you logging in before: I suggest that you create a free account to make your changes. (Though I admit that I sometimes did changes without logging in, such as the removal of the Cape Town line in the top-right table a few minutes ago.) I look forward to any future collaboration to Wikipedia on your part. Thanks again. CielProfond (talk) 19:31, 24 July 2008 (UTC)[reply]

In 1907 the Royal Observatory of Belgium (Uccle, Brussels) joined the Carte Du Ciel project, but it is not in the list on the article. There's still a 'Carte du Ciel' building (with a 1908 telescope) at the Brussels observatory. Brussels also later joined the 'Photographic Catalogue' project and continued working on this until 1964. Source: http://www.observatoire.be/NL/info/geschied.php (in Dutch). —Preceding unsigned comment added by 193.190.231.130 (talk) 14:17, 25 August 2008 (UTC)[reply]

Indeed, Uccle and some other participating observatories, had been omitted - I have now updated and expanded the table. An important point is that the Carte du Ciel and the Astrographic Catalogue are not synonymous - they were two parts of the same undertaking. I have updated and expanded accordingly. Archie carnforth (talk) 12:18, 9 December 2008 (UTC)[reply]

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Contrast with Gaia DR2

Given the Gaia (spacecraft) survey, this is out-of-date:

> the resulting Tycho-2 Catalogue (compiled at the Copenhagen University Observatory under the leadership of Erik Høg) is now the largest, most accurate and most complete, star catalogue of the brightest stars on the sky. It is currently the basis for deriving positions for all fainter stars on the sky.

See https://elibrary.ru/item.asp?id=41112927

I'm not sure if anything before Gaia DR2 in 2017 exceeded Tycho-2's accuracy for proper motions. ★NealMcB★ (talk) 18:13, 12 September 2022 (UTC)[reply]