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February 14, the 6-m mirror having been repolished for the last ten years at the Lytkarino Optical Glass Factory (LZOS, Lytkarino, Moscow Region) was delivered to the Big Altazimuth Telescope (BTA) in Nizhny Arhyz

The mirror was manufactured by the LZOS in 1974 and brought to SAO RAS. It was used at the BTA telescope for five years being its main part. Systematic astronomical observations were carried out with it until 1979, when it was replaced by a new mirror manufactured at the same LZOS factory. The old mirror was stored in a hermetically sealed container and not used since. In 2004, it was apparent that the new mirror was strongly corroded, its surface was destroyed resulting from several cleanings and repolisments. It was decided then to take the first mirror to the factory in order to renovate it. In 2007, the first mirror lying in the container was carried to Lytkarino (https://www.sao.ru/hq/sekbta/GZ_1/GZ_1.html).
The deputy technical chief of SPC-95 (LZOS) Vladimir E. Patrikeev informed us that the 8-mm glass layer was removed from the surface of the mirror, then its shape was improved, and the mirror was polished. As a result of these actions, the quality of the mirror has significantly improved; only 3% of initial deficiencies remain.

Now we are going to replace the mirror, which has been working for the BTA for almost 40 years, with the newly-arrived and improved. This is a technically difficult task that requires great knowledge, vast experience, and pinpoint accuracy.

Specialists of the BTA operation service (BOS) will be performing it for several months. This May, observations at the telescope will be stopped, and then it will come into operation with the renovated mirror already.

We wish successful work to the BTA staff and to the astronomers - justifying their hopes on the new mirror.

Philippova E.A.