An Optical Daytime Astronomy Pathfinder for the Huntsman Telescope

Abstract: Observing stars and satellites in optical wavelengths during the day (optical daytime astronomy) has begun a resurgence of interest. The recent dramatic dimming event of Betelgeuse has spurred interest in continuous monitoring of the brightest variable stars, even when an object is only visible during the day due to their proximity to the Sun. In addition, an exponential increase in the number of satellites being launched into low Earth orbit in recent years has driven an interest in optical daytime astronomy for the detection and monitoring of satellites in space situational awareness (SSA) networks. In this paper we explore the use of the Huntsman Telescope as an optical daytime astronomy facility, by conducting an exploratory survey using a pathfinder instrument. We find that an absolute photometric accuracy between 1 - 10% can be achieved during the day, with a detection limit of V band 4.6 mag at midday in sloan g and r wavelengths. In addition we characterise the daytime sky brightness, colour and observing conditions in order to achieve the most reliable and highest signal-to-noise observations within the limitations of the bright sky background. We undertake a 7 month survey of the brightness of Betelgeuse during the day and demonstrate that our results are in agreement with measurements from other observatories. Finally we present our preliminary results that demonstrate obtaining absolute photometric measurements of the International Space Station during the day.