The desirability and feasibility of determining distances to globular clusters, independently of field star calibrations using the Baade-Wesselink method is discussed. As a preliminary test of the method, simultaneous, accurate photometric and radial velocity data for the cool, lightly reddened field RR Lyrae variable VY Serpentis are presented. The data are used to solve for the star's radius and distance, using two versions of the Baade-Wesselink method that each allow for the star's low metallicity and its changing gravity. For both versions of the method, a phase difference of Delta phi approximately 0.075, between the photometric and spectroscopic radii, is found. It is concluded that the problem arises not from the method or its basic assumptions, but rather from the choice of a star with strong convection which has not been properly taken into account.
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Carney et al. (1984) studied this question.