2023 Author: Bryan Walter | [email protected]. Last modified: 2023-05-21 22:24
The former mirror was returned to the largest Russian optical telescope - the six-meter BTA -, one of the employees of the Special Astrophysical Observatory told N + 1. The updated mirror, which was installed on the telescope in December 2018 after ten years of processing at the Lytkarino optical glass plant, was removed, its fate will be decided by the commission.
BTA is one of the twenty largest telescopes in the world, it was built in 1975. The very first mirror installed on it turned out to be of poor quality - a significant part of its surface was occupied by so-called polishing (air bubbles remaining in the glass). Therefore, four years later, a spare mirror was supplied to the telescope, which was operated until 2018. The surface of this mirror also degraded, so in the early 2000s the idea arose to restore the first mirror and in 2007 it was sent to the Lytkarino Optical Glass Plant for processing. At the factory, a layer of glass about eight millimeters thick was removed from it and re-polished.
In mid-February 2018, the updated mirror was brought to the SAO and installed on the telescope. However, measurements have shown that the mirror does not fully comply with the terms of reference, and some scientists say that the updated mirror is even worse than the old one. The scientists decided to make the final diagnosis based on the results of test observations. To do this, the glass mirror was covered with a layer of aluminum about 100 nanometers thick (only with it the mirror can reflect light well; the glass surface of the mirror itself can reflect no more than five percent of the incident light).
After test observations in early June, the CAO management decided to remove the updated mirror and install the old one that worked on it until the end of 2018. Then the vice-president of the Russian Academy of Sciences, scientific director of the SAO Yuri Balega told N + 1 that the fate of the mirror would be decided by a commission, which included representatives of the observatory, the Lytkarinsky plant, as well as LOMO and NPO Optics. The commission will discuss the results of technical observations with the new mirror, its parameters and their compliance with the terms of reference.
The updated mirror was removed from the telescope on June 18 and placed in a container. Today, July 2, after a week of preparation and pauses due to bad weather, the old mirror was installed in the telescope barrel. Now CAO specialists will begin to install temperature sensors and unloading devices on the mirror - mechanical devices that ensure an even distribution of the forces acting on the mirror. The telescope is expected to start operating on schedule from October 1.
Read more about the history of the BTA telescope mirror in our article "The second approach to the mirror".
