Ages of six intermediate-age Large Magellanic Cloud star clusters have been estimated using the time dependent behavior of the luminosity of stellar interior models of red giants. All clusters studied, NGC 1783, NGC 1868, NGC 1978, NGC 2121, NGC 2209, and NGC 2231, were found to have ages < 109 yr. It is concluded that there is currently no substantial evidence for a major cluster population of large, populous clusters > 109 yr in the Large Magellanic Cloud.

Ages of six intermediate-age Large Magellanic Cloud star clusters have been estimated using the time dependent behavior of the luminosity of stellar interior models of red giants. All clusters studied, NGC 1783, NGC 1868, NGC 1978, NGC 2121, NGC 2209, and NGC 2231, were found to have ages < 109 yr. It is concluded that there is currently no substantial evidence for a major cluster population of large, populous clusters > 109 yr in the Large Magellanic Cloud.

Some simple comparisons have been made between models of main sequence (MS) stars and the Hyades main sequence with the aim of investigating the effects of small changes in the stellar opacities, the zero point of the temperature scale and the assumed distance modulus for Hyades cluster have on the inferred metallicity of the Hyades. Three grids of MS models were constructed using the Cox and Stewart (1970a,b) opacities. Furthermore, taking a rather conservative view with regard to future changes in opacity compilations, another grid was constructed with opacities 20% higher than the Cox-Stewart opacities. Following the procedure outlined by Gough and Weiss (1976), the mixing length required for constructing a solar model was found to be 1.36. Because recent photometric and spectroscopic work (Barry et al. 1978; Hardorp 1978) suggests that the sun may be redder than traditionally believed, i.e., (B-V)⊙ = 0.66–0.67 instead of 0.63 mag, two temperature scales have been used to transform the MS models to the CM diagram.

Theoretical zero age main sequences (TZAMS) from Flower (1976) are compared with two observed zero age main sequences (ZAMS) in Fig. 1.: ZAMS40, based on a distance of 40 pc (Sandage 1957) and ZAMS46 on a distance of 46 pc (see Flower 1977 for Teff: (B-V): BC scales). Although ZAMS46 lies above any TZAMS, the TZAMS can be shifted in luminosity by changing the chemical composition.