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We use Hubble Space Telescope (HST) to reach the end of the white dwarf (WD)cooling sequence (CS) in the solar-metallicity open cluster NGC 6819. Ourphotometry and completeness tests show a sharp drop in the number of WDs alongthe CS at magnitudes fainter than mF606W = 26.050+/- 0.075. This implies an ageof 2.25+/-0.20 Gyr, consistent with the age of 2.25+/-0.30 Gyr obtained fromfits to the main-sequence turn-off. The use of different WD cooling models andinitial-final-mass relations have a minor impact the WD age estimate, at thelevel of ~0.1 Gyr. As an important by-product of this investigation we alsorelease, in electronic format, both the catalogue of all the detected sourcesand the atlases of the region (in two filters). Indeed, this patch of skystudied by HST (of size ~70 arcmin sq.) is entirely within the mainKepler-mission field, so the high-resolution images and deep catalogues will beparticularly useful.

Hubble Space Telescope observations of the Kepler-field cluster NGC 6819. I. The bottom of the white dwarf cooling sequence