uvbybeta photometry and MK spectral classification.

uvby photometry of nearly 2900 stars has been studied as a function of the MK spectral classification. A unique spectral type has been defined for each star. The photometric indices p, [m1] [c1] [u-b] which are independent of reddening and their dispersions have been studied for each spectral type and for three groups of luminosity class. For 61 stars, the MK spectral classification differs considerably from what one would expect from the indices of Str5mgren's photometry. With the help of the statistical model proposed by Deeming (1968), we have corrected the observed dispersions obtained for each spectral type of main-sequence stars. We have also studied the unreddened indices ( y) c1 , m1 as well as their dispersions for the same samples. Key words: uvby photoelectric photometry - MK spectral classification - dispersions