Challenges of high-resolution spectroscopy in the Nasmyth focuses of the BTA

The article discusses the challenges and solutions associated with high-resolution spectroscopy on alt-azimuth mount telescopes, particularly focusing on the 6-meter BTA (Big Telescope Alt-Azimutal) and its Nasmyth focus. The main attention is given to the instability of spectra caused by the design features of the telescope and the equipment used. Special attention is paid to the issues of temperature non-uniformity and its impact on observation quality. Various stages of equipment development and testing are described along with the results of applying new technologies and methods to achieve high spectral resolution.