DEMONEX: the DEdicated MONitor of EXotransits

Abstract

The DEdicated MONitor of EXotransits (DEMONEX) is a low-cost, 0.5 meter, robotic telescope assembled mostly from commercially-available parts. The primary goal of DEMONEX is to monitor bright stars hosting transiting planets in order to provide a homogeneous data set of precise relative photometry for all transiting systems visible from its location at Winer Observatory in Sonoita, Arizona. This photometry will be used to refine the planetary parameters, search for additional planets via transit timing variations, place limits on the emission of the planet from secondary eclipses, and search for additional transiting planets in some systems. Despite its modest size, DEMONEX achieves a signal-to-noise ratio per transit that is comparable to that obtained with larger, 1m-class telescopes, because of its short readout time and high z-band quantum efficiency. However, the main advantage of DEMONEX is that it can be used every night for transit follow-up. With the 39 known transiting planets visible from Winer Observatory, over 90% of all nights have at least one full event to observe. We describe the hardware, and the scheduling, observing, and data reduction software, and we present some results from the first two years of operation. Synoptic surveys coming online will undoubtedly uncover a plethora of variable objects which will require inexpensive, robotic, dedicated telescopes to adequately characterize. The outline followed and lessons learned from this project will be broadly applicable for constructing such facilities.