Iqueye is a single photon counting very high speed photometer built for the ESO 3.5m New Technology Telescope
(NTT) in La Silla (Chile) as prototype of a 'quantum' photometer for the 42m European Extremely Large Telescope (E-ELT).
The optics of Iqueye splits the telescope pupil into four portions, each feeding a Single Photon Avalanche Diode
(SPAD) operated in Geiger mode. The SPADs sensitive area has a diameter of 100 μm, with a quantum efficiency better
than 55% at 500 nm, and a dark count less than 50 Hz. The quenching circuit and temperature control are integrated in
each module. A time-to-digital converter (TDC) board, controlled by a rubidium oscillator plus a GPS receiver, time tags
the pulses from the 4 channels. The individual times are stored in a 2 TeraByte memory. Iqueye can run continuously for
hours, handling count rates up to 8 MHz, with a final absolute accuracy of each time tag better that 0.5 ns. A first very
successful run was performed in Jan 2009; both very faint and very bright stars were observed, demonstrating the high
photometric quality of the instrument. The first run allowed also to identify some opto-mechanical improvements, which
have been implemented for a second run performed in Dec 2009. The present paper will describe the first version, the
improvements implemented in the second one, and some of the obtained astronomical results.