On the Effectiveness of Observations in the Mid-Infrared Wavelength Range on the 2.5-Meter Telescope of the Caucasus Mountain Observatory of Moscow State University with Commercial IR Cameras

Abstract: The main factors that influence the success of observations in the infrared range (central wavelengths of the photometric bands at 3.75 and 4.8~$\mu$m) on the multipurpose optical telescope are considered. Estimates of the sky background brightness are obtained for the Caucasus Mountain Observatory (CMO) of Moscow State University: $1.3\cdot10<sup>6$~photons/(s pixel) in the 3.75~$\mu$m band and $3.4\cdot10<sup>6$~photons/(s pixel) in the 4.8~$\mu$m; and the instrumental background for the 2.5-m CMO telescope at $0<sup>\circ$C: $3.2\cdot10<sup>6$~photons/(s pixel) in the 3.75~$\mu$m band and $4.3\cdot10<sup>6$~photons/(s pixel) in the 4.8~$\mu$m band. It is shown that at this background signal level with the currently available commercial cameras in the $3-5$~$\mu$m spectral range, the telescope-camera coupling capabilities for observing faint objects will still be limited by the thermal background. For different observational conditions, estimates of the limiting magnitudes of objects available for observations in the 3.75 and 4.8~$\mu$m ranges are obtained. For average observation conditions (instrument temperature of $0<sup>\circ$C and stellar image size of 1 arcsec), the limit is $\sim10.6<sup>m$ and $\sim8.4<sup>m$, respectively.