[Previous] | [Session 15] | [Next]
R. P. Boyle (Vatican Observatory), A. G. Davis Philip (Union College and ISO), F. Smriglio, A. Dasgupta (University of Rome), A. Kazlauskas, V. Straizys (ITPA, Vilnius)
For our observational program on stellar clusters to calibrate the Strömvil Photometric System (the four Strömgren u v b y and the three Vilnius P Z S filters), we use the Lennon Telescope (VATT) of the Vatican and Steward Observatories on Mt. Graham. We have observed the open cluster M 67 wherein much photometry both photoelectric and CCD already exists. Multiple exposures with the telescope offset by small (10 arcsec) and larger (2 arcmin) amounts and with the derotator offset by 180 degrees tell what is the photometric uncertainty attained. The flatfielding of the CCD has been significantly improved by adding black velvet inside the "top hat" baffle tube and the hole of the primary mirror in order to suppress scattered light. The multiple exposures in M 67 now show photometric error in the instrumental system of less than 0.015 mag RMS. And the transformation into the standard Strömvil System by use of stellar standards shows a successful fit to 0.015 RMS in all seven filters. Thus learning the color transformation equations we are prepared to calibrate other star fields in the Strömvil System for stellar classification.