Detection of optical photons from stars using a STJ device

A goal of this study is to develop the STJ's as multi-wavelength imager for ground-based optical astronomy. We designed optics to measure continuous photon rate using STJ device as a first step of astronomical observation, because our device and readout system can not detect a response of single photon at optical wavelengths. The beam of telescope was directory focused on a STJ device operated at 0.3 K stage of 3He cryostat. The beam was modulated around 400 Hz using a chopper wheel. Response of a STJ device was read out using charge sensitive amplifier and lock-in amplifier. Test observation was carried out in 9th-13th Sep 2002 using the Infrared Simulator, which is a 1.5m-diameter telescopes located at the National Astronomical Observatory of Japan. A STJ device, which fabricated at RIKEN, was placed at the Nasmyth focus of the Infrared Simulator. α UMa and for α Cyg are observed and the response for the optical photons are detected. (author)