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R.P. Boyle (Vatican Obs.), A.G.D. Philip (ISO and Union College), V. Strai\v{z}ys (ITPA, Vilnius)
Use of the Strömgren four-color photometric system with the addition of three filters (P, Z, S) of the Vilnius system allows classifying all the types of stars, even in the presence of significant reddening by interstellar dust (Straizys et al, 1996). With this Strömvil system we have begun a long-term observational program on the Vatican Advanced Technology Telescope (VATT) on Mt. Graham, Arizona, (see Philip et al,1996). The Loral 2K by 2K CCD, prepared by M. Lesser of the University of Arizona CCD Lab, gives as high as 90% quantum efficiency in most of the filters and notably 65% at the u filter. To demonstrate the degree of success so far attained in this CCD Strömvil System, we present preliminary results on the open cluster M67. We will compare some of our photometry with the CCD results of B. A. Twarog (1987) and the photoelectric photometry of Nissen et al. (1987).
REFERENCES
Nissen, P.E., Twarog, B.A., and Crawford, D.L. 1987, A.J. 93,634
Philip, A.G. Davis, Boyle, R.P., Straizys, V. 1996, Baltic Astronomy,5,445
Straizys, V., Crawford, D.L., Philip, A.G.Davis 1996, Baltic Astronomy, 5,83
Twarog, B.A. 1987, A.J. 93,647