aTmcam: A Simple Atmospheric Transmission Monitoring Camera For Sub 1% Photometric Precision

• Published in: arXiv.org 2013-02
• Main Authors: Li, Ting, DePoy, D L, Kessler, R, Burke, D L, Marshall, J L, Wise, J, J -P Rheault, Carona, D W, Boada, S, Prochaska, T, Allen, R
• Format: Article
• Language: English
• Subjects: Atmospheric models; Color; Narrowband; Photometry; Water absorption
• ISSN: 2331-8422

Traditional color and airmass corrections can typically achieve ~0.02 mag precision in photometric observing conditions. A major limiting factor is the variability in atmospheric throughput, which changes on timescales of less than a night. We present preliminary results for a system to monitor the throughput of the atmosphere, which should enable photometric precision when coupled to more traditional techniques of less than 1% in photometric conditions. The system, aTmCam, consists of a set of imagers each with a narrow-band filter that monitors the brightness of suitable standard stars. Each narrowband filter is selected to monitor a different wavelength region of the atmospheric transmission, including regions dominated by the precipitable water absorption and aerosol scattering. We have built a prototype system to test the notion that an atmospheric model derived from a few color indices measurements can be an accurate representation of the true atmospheric transmission. We have measured the atmospheric transmission with both narrowband photometric measurements and spec- troscopic measurements; we show that the narrowband imaging approach can predict the changes in the throughput of the atmosphere to better than ~10% across a broad wavelength range, so as to achieve photometric precision less than 0.01 mag.