Astronomy & Astrophysics

Table 1: Observing log for the programme clusters. All clusters were observed on one night by Iliev (II), Maitzen (HM), and Netopil (MN).
Table 2: Summary of results; the age, distance modulus, reddening and thus the distance from the Sun was derived by fitting isochrones to the $\Delta a$ photometry. R_V was set to 3.1, except for NGC 1502, for which Pandey et al. (2003) list 2.57. The distance of the Sun from the galactic center R₀ was set to 8.5 kpc. The errors in the final digits of the corresponding quantity are given in parenthesis.
Table 3: The regression coefficients for the transformations and normality lines. The absolute values and errors vary due to the inhomogeneous "standard'' observations (photographic, photoelectric, and CCD) found in the literature as well as the dependence on the magnitude range in common, i.e. a broader range guarantees a small error. The offsets are due to the four different telescopes and thus instruments as well as CCD used (Table 1). The errors in the final digits of the corresponding quantity are given in parenthesis.