2006PASP..118..716L

This paper summarizes a three-night observing campaign aimed at achieving millimagnitude-precision photometry of bright stars (V < 9.0 mag) with the 1 m Swope Telescope at Las Campanas Observatory. The test targets were the main-sequence stars HD 205739 and HD 135446. The results show that by placing a concentric diaphragm in front of the aperture of the telescope, it is possible to avoid saturation and achieve a photometric precision of 0.0008-0.0010 mag per data point, with a cadence of less than 4 minutes. It is also possible to reach an overall precision of less that 0.0015 mag for time series of 6 hr or more. The photometric precision of this setup is only limited by scintillation. Scintillation could be reduced, and therefore the photometric precision further improved, by using a neutral-density filter instead of the aperture stop. Given the expected median depth of about 0.01 mag for extrasolar-planet transits, plus their typical duration of several hours, the results of this paper show that 1 m telescopes equipped with standard CCDs can be used to detect planet transits as shallow as 0.002 mag around bright stars.