Abstract
A system of visual classification of the strength of the interstellar band 4430 A has been developed, based on spectra taken at spectral classification dispersion. The intensity of the band was divided into 8 main classes, defined by a group of selected standard stars. The system was applied to 1,111 southern OB stars contained in the catalog of spectral types by Garrison, Hiltner, and Schild (1977). The mean error in the classification was estimated to be plus or minus 1 class. Equivalent widths were measured for 100 stars; an excellent correlation with the visual estimations was obtained. A calibration between these two parameters is given.
