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

TL;DR

The paper introduces a simple atmospheric transmission monitoring camera system, aTmCam, designed to achieve sub-1% photometric precision by accurately tracking atmospheric variability using narrow-band imaging of standard stars.

Contribution

The novel aTmCam system uses narrow-band filters and standard stars to monitor atmospheric transmission, enabling photometric precision below 1%, improving upon traditional correction methods.

Findings

aTmCam can predict atmospheric throughput changes better than 10%

The system achieves photometric precision less than 0.01 mag

Narrowband imaging effectively models atmospheric transmission

Abstract

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.