Aqueye Plus: a very fast single photon counter for astronomical photometry to quantum limits equipped with an Optical Vortex coronagraph

In recent years, w e developed two very high speed single photon photometers, Aqueye and Iqueye , as prototypes for ³TXDQWXP´ photometers for the Extremely Large Telescopes of the next decade . The se instrume nts , based on single photon avalanche photodiodes and a 4-fold split-pupil concept, have been successfully used to obtain data of the highest quality on optical pulsars . Subsequently, we performed an attempt to utilize the Orbital Angular Momentum and asso ciate d Optical Vorticity to achieve high performance stellar coronagraph y. Presently, we are making a synergic effort in building Aqueye Plus , a new instrument for the 1.8 m telescope of the Asiago - Cima Ekar Observatory, which combines both functions, na mely high speed sim ultaneous multicolor photon counting photometry and stellar coronagraphy . The innovative capability of Aqueye Plus is to take advantage of the two parall el outputs (NIM and TTL) of the four high time accuracy photon counting sensors . The NIM output preserve s the best timing capability, while the TTL output drive s a deformable 32 -element mirror in a sort of quadrant detector to correct for defocus and tip/tilt aberration s of the stellar image on the phase mask discontinuity. Th is paper d escribe s the Aqueye Plus instrument main characteristics and its foreseen performance . Keywords : quantum astronomy, single photon photometry, astronomical coronagraphy, orbital angular momentum, optical vorticity