The Ducati alpha photometric system

Basic Reference

Strauss F.M., Ducati J.R. 1981, A&A Suppl. 44, 337


A set of 168 stars of spectral types B0 to G5, luminosity classes I to V with well determined beta indices were observed with a pair of Halpha filters (37 and 208A bandwidth) to establish a common set of standard stars for Halpha and Hbeta photometry. The new standard alpha indices were obtained simultaneously from a weighted least squares solution of almost 2000 observations made on 54 nights over a two year period, by a methode described in the text. The average r.m.s. accuracy of each standard alpha index is 0.002. A comparison is made with other system. An application of alpha and beta photometry to the study of supergiants showed that is possible to:
a) separate them from lower luminosity stars,
b) divide them into early and late types, and
c) derive color excesses.


Access to the data and references

Asiago Database on Photometric System (ADPS)

Indices and Parameters



Definition of the Halpha filters:


EMI 9658AR, extended S20 cathode
Please, send your commentsto
Last update: 21 May 1996