A Comparison of the Luminosities of Perseus-Arm Stars in the Hγ and MK Systems

Stars ascribed to the Perseus arm on the basis of their interstellar lines are used to compare absolute magnitudes determined from MK spectral types with those derived from H equivalent widths. For the majority of these stars (BOA3 supergiants) there are no significant differences in the luminosities determined from the two methods and random errors appear to be of com arable magnitude. The random errors are considerably reduced (to about 0.3 mag) by taking means oft e MK and H absolute magnitudes, especially for stars which are variable in velocity.