Time-resolved photometry using a CCD

From a study of two methods for the use of CCDs as photometers, it is shown that high-precision relative photometry of variable stars is possible using a CCD detector under nonphotometric conditions with good time resolution and a fainter magnitude limit than is possible with photomultipliers. The method consisting of trailing a group of stellar images along columns of the CCD at a rate of several seconds of time per pixel is useful for brighter objects, and the time resolution can be substantially shorter than one second. The method involving the taking of repeated short exposures of a particular star field containing the star of interest can be used on faint stars of V greater than 15 provided that the required time resolution is not less than about 15 seconds. Stars as faint as V of 18.5 were observed with time resolutions of three minutes and photometric accuracy of better than 0.04 magnitude using the repeated exposure method. 8 references