The optomechanical design of AquEYE, an instrument for astrophysics on its shortest timescales at the Asiago Observatory

This paper describes the ultra-fast photometer AquEYE (the Asiago Quantum Eye) being built for the 182 cm telescope at Cima Ekar, as a prototype for the QuantEYE instrument studied for the ESO OWL. In a way similar to what has been proposed for Quanteye, Aqueye isolates a single object at the center of the telescope field of view, and divides the telescope pupil in four parts. Each sub-pupil is then focused on a Single Photon Avalanche Photodiode capable to tag the arrival time of each photon to better than 50 picoseconds. The counts are acquired via a Time to Digital Converter board and stored in four separate memories. Both in-line and off-line algorithms will be available for data analysis. The designed optical non-imaging solution concentrates all the light collected inside a 3 arcsec field on the 50 micrometer detector square area. Different filters can be inserted in the 4 different optical paths. It is foreseen to utilize the instrument on several different astrophysical problems characterized by rapid variability, including occultations by the Moon, asteroids and KBOs, and extrasolar planet transits.