How do you Display the USNO-B1.0 Catalogue?

C2A lets you load the USNO-B1.0 catalogue directly from the server VizieR of the Centre des Données Astronomiques de Starsbourg. You must be connected to the Internet to load and display objects from this catalogue. To display the USNO-B1.0 stars in an area, proceed as follows:

Display a field less than 4°. Because the USNO-B1.0 catalogue is enormous (more than a billion objects), the transfer time would be prohibitive if the field were more than 4°.

SHIFT+right-click on the displayed map. Select the USNO-B1 catalogue in the contextual menu which appears (or verify that this catalogue is already selected – if you re-click on a catalogue already selected, it will no longer be displayed).

Remaining in the map, right-click and select the command Load USNO-B1.0. This command is not available if the current database is not the USNO-B1.0 catalogue. C2A then automatically displays the remote catalogues dialogue box and proceed with the transfer from the VizieR at CDS. The zone to be populated is divided in 30’ sub-zones in width and height in order to facilitate transfers.

When databases have been loaded from the VizieR server, they are held in a cache by C2A, that is to say, a set of files managed by C2A. It is therefore unnecessary to load areas which have already been accessed, and these can be displayed without being connected to the Internet.

After a while the cache of USNO-B1.0 data can become too big. You can then clear the cache using the remote catalogues dialogue box.

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