aat Acta Astrophys. Tau. Acta Astrophysica Taurica 2712-925X Kiselev Nikolai Nikolaevich, Mosсow, settlement Moskovskii, Tat'yanin Park Str., 12, Moscow, Russia. RU 130 KRCSIG Research articles New optics of the 1.25 m telescope AZT-11 of the Crimean Astrophysical Observatory Terebizh Valery Yu. Steshenko Natalya M. Dolgopolov Andrei V. Antonyuk Kirill A. Rostopchina-Shakhovskaya Alla N. Crimean Astrophysical Observatory, Nauchny 298409 Crimean Astrophysical Observatory, Nauchny 298409 Crimean Astrophysical Observatory, Nauchny 298409 Crimean Astrophysical Observatory, Nauchny 298409 Crimean Astrophysical Observatory, Nauchny 298409 29 09 2026 7 3 15 20 23 09 2026 Copyright (c) 2026 Valery Yu. Terebizh, Natalya M. Steshenko, Andrei V. Dolgopolov, Kirill A. Antonyuk, Alla N. Rostopchina-Shakhovskaya 2026 Valery Yu. Terebizh, Natalya M. Steshenko, Andrei V. Dolgopolov, Kirill A. Antonyuk, Alla N. Rostopchina-Shakhovskaya The metadata for this submission is licensed under a Creative Commons Attribution 4.0 International License. Copyright and publishing rights for texts published in Acta Astrophysica Taurica is retained by the authors, with first publication rights granted to the journal.Texts are free to use with proper attribution and link to the licensing (Creative Commons Attribution 4.0 International).

The AZT-11 telescope was put into operation in 1981. Over 40 years, the telescope primary mirror has been repeatedly recoated with aluminium. As a result, the mirror surface quality has substantially degraded, causing an increase in instrumental polarization among other adverse effects. Taking into account the parameters of the original telescope system (F = 16 m), which are poorly fit to modern light detectors, as well as the availability of a CO-115 sitall blank of appropriate size, a new optical system was designed and manufactured. We present data on the new optical system and discuss challenges during its development and manufacture, as well as the techniques and methods employed.

telescope optical system modernization The work was carried out within the framework of the state assignment of the FSBIS “CrAO RAS”. Maksutov D.D., 1946. Astronomical optics. M.: Gostekhizdat. (In Russ.) Mikhel’son N.N., 1976. Optical telescopes. M.: Nauka. (In Russ.) Piirola V., 1975. Ann. Acad. Sci. Fennicae, Ser. A VI – Physica, vol. 418. Terebizh V.Yu., 2014. Mon. Not. Roy. Astron. Soc., vol. 440, pp. 1824–1827. Terebizh V.Yu., 2019. Survey Telescope Optics. Bellingham, WA: SPIE Press.