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Fig. 2


Strömgren diagnostic diagrams obtained from deep STELLA/WiFSIP uvbyβ photometry. a) De-reddened color-color diagram (uv) versus (by); b) color difference c1 = (uv)−(vb) versus the blanketing difference m1 = (vb)−(by); c) Hβ index versus by color; d)V magnitude versus de-reddened color difference c1. The line is the 890 Myr isochrone with solar metallicity. The light-gray dot would be a Sun in IC 4756. We note that in panels a)c) only stars with photometric errors smaller than 001 are plotted, i.e., typically brighter than 17th magnitude in y.

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