2023 Author: Bryan Walter | [email protected]. Last modified: 2023-05-21 22:24
The management of the Special Astrophysical Observatory of the Russian Academy of Sciences decided to remove an updated mirror from the 6-meter BTA telescope, which was installed on the telescope in December 2018 after 11 years of processing at the Lytkarino Optical Glass Plant. The corresponding order was signed on Monday by the director of the CAO, one of the observatory employees told N + 1. Astronomical observations with the updated mirror lasted less than six months, now an old mirror, which has been used for almost 40 years, will be installed, on which a new reflective layer will be applied.
BTA is the largest telescope in Russia, it is located in the mountains of the Western Caucasus. Now BTA is one of the twenty largest telescopes in the world. The very first mirror, installed on the BTA in 1975, 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 second mirror was installed on the telescope, which was used 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 8 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. The first measurements showed that the mirror does not fully comply with the technical specifications, and some scientists said that the updated mirror is even worse than the old one. However, 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 aluminizing, technical observations with a telescope began: scientists observed bright stars with it, measured the characteristics of the mirror surface, and took Hartmannograms. In December 2018, scheduled observations at the telescope began in accordance with the schedule.
But the quality of the mirror really turned out to be no higher than the old one. “The mirror showed itself as predicted: high-resolution spectroscopy is impossible with it, even half of the previous results could not be obtained on (spectrograph) SCORPIO, speckle interferometry does not work as it should. The image quality is terrible,”another observatory employee told N + 1.
Now the mirror will be removed, by the end of August it is planned to install the old mirror in its place, in September it will be adjusted and adjusted. It is expected that the telescope will start working on schedule from October 1, the filmed mirror will be stored in a container next to the observatory tower.
Updated: the vice-president of the Russian Academy of Sciences, scientific director of the SAO Yuri Balega told N + 1 that following the meeting on June 4, it was decided to create a commission that would decide the fate of the mirror.
It will include 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.
According to Balega, the opinions of astronomers about the quality of the mirror were divided: some believe that observations can be made with it, others insist on replacing it. The mirror, Balega noted, is suitable for observing stars, but its quality is not enough for studying faint extragalactic objects. The commission is expected to make a decision by the end of June. She can send it for revision, or recognizes it of sufficient quality to work on a telescope.