  This paper presents a prototype of an infrared photometer, created at SAI of
MSU based on the commercial infrared module Gavin-615A. The operating spectral
range of the photometer is 3-5 mkm. 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 approx 5% across the entire
signal range, and coefficients for correction functions were determined.
Additionally, we determined the readout noise RN=1200+-210 e-, the conversion
coefficient GAIN=520+-9 e-/ADU, the signal magnitude of the bias frame BIAS =
960.5+-2.2 ADU, and the dark current 9.3e6 +-1.1e6 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 6C. 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". 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-second exposure time and a SNR=10. It is shown that at high image
quality with SNR=3 and exposure of 20 seconds it is possible to observe stars
up to L=9 mag and M=8 mag. The main module of the photometer was also used in
measurements of the sky background brightness.
