The engineers of Fesenkov Astrophysical Institute in collaboration with Astrotechpribor company have upgraded the optical system of Assy-Turgen 1.5-m telescope, the largest telescope in Kazakhstan. In the direct focus of the telescope they installed the 4-lens quartz field corrector with the diameter of 280 mm.

After upgrade, the field of view of the telescope has increased 17.5 times and now amounts to 22.3×22.3 angular minutes at the CCD camera. In perspective, the telescope will allow to obtain images up to one square degree in spectral range from 300 nm to 2.5 μm, significantly increasing the efficiency of AZT-20 at search and survey tasks. Besides, inclusion of large amount of astronomical standards into a single CCD allows to increase the precision of astrometrical and photometrical observations.

AZT20 in construction
Computation of optical parameters of AZT-20 with focus reducer

To perform benchmark of the new optical system the Orion Nebula as well as an area in the Milky Way were chosen. The deviations of the obtained parameters from the predicted ones amounted to less than 0.1%. The upgraded telescope will allow to broaden the scope of tasks in studying deep space objects and to attract international collaborators.

Field_FL_AZT20 Orion-AZT20
Star field used for measuring the actual focal distance (5 714.4 мм). The deviation from the calculated values is less than 0.1% (6.09 мм). The Orion Nebula (NGC 1976). The field is 22.3×22.3 angular minutes. CCD Apogee U9000, Astrodon RGB gen 2 filter, RGB sum (Rx 30 sec, Gx 30 sec, Bx 60 sec)