Andrew W. Mann, Eric Gaidos, Greg Aldering
We demonstrate ground-based submillimagnitude (<10^-3) photometry of widely
separated bright stars using snapshot CCD imaging. We routinely achieved this
photometric precision by (1) choosing nearby comparison stars of a similar
magnitude and spectral type, (2) defocusing the telescope to allow high signal
(>10^7 electrons) to be acquired in a single integration, (3) pointing the
telescope so that all stellar images fall on the same detector pixels, and (4)
using a region of the CCD detector that is free of nonlinear or aberrant
pixels. We describe semiautomated observations with the Supernova Integrated
Field Spectrograph (SNIFS) on the University of Hawaii 2.2m telescope on Mauna
Kea, with which we achieved photometric precision as good as 5.2x10^-4
(0.56mmag) with a 5 minute cadence over a 2hr interval. In one experiment, we
monitored eight stars, each separated by several degrees, and achieved
submillimagnitude precision with a cadence (per star) of ~17 minutes. Our
snapshot technique is suitable for automated searches for planetary transits
among multiple bright stars.
View original:
http://arxiv.org/abs/1109.1358
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