Abstract
This work presents an initial on-sky performance measurement of the Single-Photon Imager for Nanosecond Astro-physics (SPINA) system, part of our Ultra-Fast Astronomy (UFA) program. We developed the SPINA system based on the position-sensitive silicon photomultiplier (PS-SiPM) detector to record both temporal and spatial information of detected photons. The initial on-sky testing of the SPINA system was conducted on UT 2022 Jul 10, with the Nazarbayev University Transient Telescope at the Assy-Turgen Astrophysical Observatory (NUTTelA-TAO), studied stars with a wide range of brightness and a dark region of the sky without starsm, affected by atmospheric conditions; a background noise level of 1914 counts per second (cps) within this resolution element; and crosstalk probability of ~ 0.18 near the detector’s center while reaching ~ 0.5 at the edges. We derived a 5σ sensitivity of 17.45 Gaia-BP magnitude in a 1s exposure with no atmospheric extinction. Based on a false alarm rate of once per 100 nights, The SPINA system provides a transient sensitivity of 14.06 mag on a 10ms window and a 15 P.E. detection threshold forsub- μstime scale, limited by crosstalk. In addition, the SPINA system proved its capability to detect rapid alterations in the stellar profile: a variation of ±1.8% in the stellar profile FWHM under 20msexposure and ±5% change under 2msexposures, as well as capturing stellar light curves on themsand μsscales.