A Technique for Ultrahigh‐Precision CCD Photometry

We present techniques for wide‐field ultrahigh‐precision time‐sampled CCD photometry. Representing a survey of field stars, our data consist of UBVRI photometry and a V ‐band time series of exposures on 5 consecutive nights covering 11,500 stars in a ∼1 deg 2 field. The resulting light curves reach precisions of 0.0020 mag per exposure in the brightest stars (V∼14). Light curves binned and averaged over 4.5 hr reach precisions of 0.00019 mag for the brightest stars. We present example light curves and discuss one application for surveys of this type: the search for transits by extrasolar planets.