New Infrared Camera of the Caucasian Mountain Observatory of the SAI MSU: Design, Main Parameters, and First Light

Abstract

This paper presents a prototype of an infrared photometer, created at the Sternberg Astronomical Institute, Lomonosov Moscow State University (SAI MSU), based on the commercial infrared module Gavin-615A. The operating spectral range of the photometer is 3–5 \(\mu\)m. Investigations of the photometer’s detector have shown that its parameters coincide with those stated by the manufacturer. The nonlinearity of the detector does not exceed \({\sim}5\%\) across the entire signal range, and coefficients for correction functions were determined. Additionally, we determined the readout noise \(\textrm{RN}=1200\pm 210e^{-}\), the conversion coefficient \(\textrm{GAIN}=520\pm 9e^{-}/\)ADU, the signal magnitude of the bias frame \(\textrm{BIAS}=960.5\pm 2.2\) ADU, and the dark current \({\approx}(9.3\pm 1.1)\times 10^{6}e^{-}\)/s, which is the sum of the detector’s dark current and the radiation from the entrance window of the detector module. The value of dark current was measured at a window temperature of \(6^{\circ}\)C. Observations commenced with the photometer at the 2.5-m telescope of the Caucasian Mountain Observatory of MSU, with the first results presented in this paper. The unvignetted field of view was \(30^{\prime\prime}\). In the \(M\) band under good atmospheric conditions, an image quality close to the diffraction limit was achieved. Images of a star with brightness \(L=7.96\) and \(M=6.78\) were obtained over the 20-s exposure time and a \(\textrm{SNR}\sim 10\) ratio. It is shown that at high image quality with \(\textrm{SNR}=3\) and exposure of 20 s it is possible to observe stars up to \(L\sim\) 9\({}^{m}\) and \(M\sim 8^{m}\). The main module of the photometer was also used in measurements of the sky background brightness.