Datatype: UBVpg

Soon after the developement of photoelectric observations, the UBV photographic photometric extended the capabilities of photometry to observe fainter stars to make deep studies of clusters or cover a wide area. It represents a corpus of 100'000 observations. However, plates measurement techniques and a often limited number of plates in each colour result in lower precision. The errors on magnitudes and colours are generally of the order of 0.05 mag or larger. This produces the scatter observed in colour-magnitude diagrams based on photographic data. Photographic photometry is now largely replaced by CCD photometry in most systems.

UBV photometry stored in the database is still useful to make a good stellar census in the cluster areas and to prepare an observing campaign. Detailed studies of the cluster CMDs require however better precision data.

Record structure

No:Star number
Ref:Data source
V:V magnitude
B-V:B-V colour index
U-B:U-B colour index

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Last Update: 17 February 1998