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A. G. D. Philip (ISO and Union College), R. P. Boyle (Vatican Observatory), R. Janusz (University School ``Ignatianum", Krakow and Vatican Observatory)
The Vatican Advanced Technology Telescope on Mt. Graham is being used in a program of CCD photometry of open and globular clusters. We are using the Ströomvil System (Straizys et al. 1996), a combination of the Strömgren and Vilnius Systems. This system allows stars to be classified as to temperature, surface gravity, metallicity and reddening from the photometric measures alone. However, to make accurate estimates of the stellar parameters the photometry should be accurate to 1 or 1.5 percent. In our initial runs on the VATT we did not achieve this accuracy. The problem turned out to be scattered light in the telescope and this has now been reduced so we can do accurate photometry. Boyle has written a routine in IRAF which allows us to correct the flats for any differences. We take rotated frames and also frames which are offset in position by one third of a frame, east-west and north-south. Measures of the offset stars give us the corrections that need to be made to the flat. Robert Janusz has written a program, the CommandLog, which allows us to paste IRAF commands in the correct order to reduce measures made on a given observing run. There is an automatic version where one can test various parameters and get a set of solutions. Now we have a set of Strömvil frames in the open cluster, M 67 and we compare our color-magnitude diagram with those of BATC (Fan et al. 1996) and Vilnius (Boyle et al. 1998). A preliminary report of the M 67 photometry will be found in Laugalys et al. (2004). Here we report on a selected set of stars in the M 67 frames, those with errors 1 percent or less.
The author(s) of this abstract have provided an email address for comments about the abstract: agdp@union.edu
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Bulletin of the American Astronomical Society, 37 #2
© 2005. The American Astronomical Soceity.