Measurement of atmospheric scintillation during a period of Saharan dust (Calima) at Observatorio del Teide, Iza\~na, Tenerife, and the impact on photometric exposure times

TL;DR

This study measures atmospheric scintillation noise during Saharan dust events at Tenerife, showing that noise decreases with frequency and that longer exposure times can be used in ground-based photometry, even during dust conditions.

Contribution

It provides the first detailed scintillation noise profiles during Saharan dust events and assesses their impact on photometric exposure times at a major observatory.

Findings

Scintillation noise reduces by half at about 5 Hz.

Noise drops to one tenth between 20-30 Hz during Calima.

Longer exposure times (>50 ms) are feasible even during dust events.

Abstract

We present scintillation noise profiles captured at the Observatorio del Teide, Iza\~na, Tenerife, over a one-week period in September 2017. Contemporaneous data from the Birmingham Solar Oscillations Network (BiSON) and the Stellar Activity (STELLA) robotic telescopes provides estimates of daily atmospheric extinction allowing the scintillation noise to be placed within the context of overall atmospheric conditions. We discuss the results both in terms of the impact on BiSON spectrophotometer design, and for astronomical observations more generally. We find that scintillation noise power reduces by half at about~\SI{5}{\hertz}, and is reduced to one tenth between~\SIrange{20}{30}{\hertz} even during periods of mild Calima, where visibility is reduced due to high concentrations of mineral dust in the atmosphere. We show that the common accepted exposure time of~\SI{<10}{\milli\second} for limiting the effect of scintillation noise in ground based photometry may be increased, and that depending on the application there may be little benefit to achieving exposure times shorter than~\SI{50}{\milli\second}, relaxing constraints on detector gain and bandwidth.