The first telescope was built in 1609 by the Italian astronomer Galileo Galilei. The scientist, based on rumors about the invention of the Dutch telescope, unraveled its device and made a sample, which was first used for space observations. Galileo's first telescope had modest dimensions (tube length 1245 mm, lens diameter 53 mm, eyepiece 25 diopters), an imperfect optical scheme and a 30-fold magnification. But it made it possible to make a whole series of remarkable discoveries: to detect four satellites of the planet The sun, mountains on the surface of the moon, the presence of appendages in the disk of Saturn at two opposite points.

More than four hundred years have passed - on earth and even in space, modern telescopes help earthlings look into distant cosmic worlds. The larger the diameter of the telescope mirror, the more powerful the optical setup.

multimirror telescope

Located on Mount Hopkins, at an altitude of 2606 meters above sea level, in the state of Arizona in the USA. The diameter of the mirror of this telescope is 6.5 meters.. This telescope was built back in 1979. In 2000, it was improved. It is called multi-mirror because it consists of 6 precisely fitted segments that make up one large mirror.

Magellan telescopes

Two telescopes, Magellan-1 and Magellan-2, are located at the Las Campanas Observatory in Chile, in the mountains, at an altitude of 2400 m, the diameter of their mirrors is 6.5 m each. The telescopes started operating in 2002.

And on March 23, 2012, the construction of another more powerful Magellan telescope, the Giant Magellan Telescope, began, it should come into operation in 2016. In the meantime, the top of one of the mountains was demolished by an explosion in order to clear a place for construction. The giant telescope will consist of seven mirrors 8.4 meters each, which is equivalent to one mirror with a diameter of 24 meters, for which he was already nicknamed “Seven-eye”.

Separated twins Gemini telescopes

Two brother telescopes, each located in a different part of the world. One - "Gemini North" stands on top of an extinct volcano Mauna Kea in Hawaii, at an altitude of 4200 m. The other - "Gemini South", is located on Mount Serra Pachon (Chile) at an altitude of 2700 m.

Both telescopes are identical the diameters of their mirrors are 8.1 meters, they were built in 2000 and belong to the Gemini Observatory. Telescopes are located on different hemispheres of the Earth so that the entire starry sky is available for observation. Telescope control systems are adapted to work via the Internet, so astronomers do not have to travel to different hemispheres of the Earth. Each of the mirrors of these telescopes is made up of 42 hexagonal pieces that have been soldered and polished. These telescopes are built with state-of-the-art technology, making Gemini Observatory one of the most advanced astronomy laboratories in the world today.

Northern "Gemini" in Hawaii

Subaru telescope

This telescope belongs to the Japan National Astronomical Observatory. A is located in Hawaii, at an altitude of 4139 m, next to one of the Gemini telescopes. The diameter of its mirror is 8.2 meters. "Subaru" is equipped with the world's largest "thin" mirror .: its thickness is 20 cm, its weight is 22.8 tons. This allows the use of a drive system, each of which transfers its force to the mirror, giving it an ideal surface in any position, for the best image quality.

With the help of this sharp telescope, the most distant galaxy known to date, located at a distance of 12.9 billion light years, was discovered. years, 8 new satellites of Saturn, protoplanetary clouds photographed.

By the way, "Subaru" in Japanese means "Pleiades" - the name of this beautiful star cluster.

Japanese telescope "Subaru" in Hawaii

Hobby-Eberle Telescope (NO)

Located in the USA on Mount Faulks, at an altitude of 2072 m, and belongs to the McDonald Observatory. The diameter of its mirror is about 10 m.. Despite its impressive size, Hobby-Eberle cost its creators only $13.5 million. It was possible to save the budget thanks to some design features: the mirror of this telescope is not parabolic, but spherical, not solid - it consists of 91 segments. In addition, the mirror is at a fixed angle to the horizon (55°) and can only rotate 360° around its axis. All this significantly reduces the cost of construction. This telescope specializes in spectrography and is successfully used to search for exoplanets and measure the speed of rotation of space objects.

Large South African Telescope (SALT)

It belongs to the South African Astronomical Observatory and is located in South Africa, on the Karoo plateau, at an altitude of 1783 m. The dimensions of its mirror are 11x9.8 m. It is the largest in the southern hemisphere of our planet. And it was made in Russia, at the Lytkarinsky Optical Glass Plant. This telescope has become an analogue of the Hobby-Eberle telescope in the USA. But it has been modernized - the spherical aberration of the mirror has been corrected and the field of view has been increased, thanks to which, in addition to working in the spectrograph mode, this telescope is capable of obtaining excellent photographs of celestial objects with high resolution.

The largest telescope in the world ()

It stands on top of the extinct volcano Muchachos on one of the Canary Islands, at an altitude of 2396 m. Main mirror diameter - 10.4 m. Spain, Mexico and the USA took part in the creation of this telescope. By the way, this international project cost 176 million US dollars, of which 51% was paid by Spain.

The mirror of the Great Canary Telescope, composed of 36 hexagonal parts, is the largest of the existing ones in the world today. Although this is the largest telescope in the world in terms of mirror size, it cannot be called the most powerful in terms of optical performance, since there are systems in the world that surpass it in their vigilance.

Located on Mount Graham, at an altitude of 3.3 km, in the state of Arizona (USA). This telescope is owned by the Mount Graham International Observatory and was built with money from the United States, Italy and Germany. The structure is a system of two mirrors with a diameter of 8.4 meters, which is equivalent in light sensitivity to one mirror with a diameter of 11.8 m. The centers of the two mirrors are at a distance of 14.4 meters, which makes the resolution of the telescope equivalent to 22 meters, which is almost 10 times greater than that of the famous Hubble Space Telescope. Both mirrors of the Large Binocular Telescope are part of one optical instrument and together they form one huge binocular - the most powerful optical instrument in the world at the moment.

Keck I and Keck II are another pair of twin telescopes. They are located next to the Subaru telescope on the top of the Hawaiian volcano Mauna Kea (height 4139 m). The diameter of the main mirror of each of the Keks is 10 meters - each of them individually is the second largest telescope in the world after the Great Canary. But this system of telescopes surpasses the Canary in terms of "vigilance". The parabolic mirrors of these telescopes are made up of 36 segments, each of which is equipped with a special computer-controlled support system.

The Very Large Telescope is located in the Atacama Desert in the Chilean Andes, on Mount Paranal, 2635 m above sea level. And belongs to the European Southern Observatory (ESO), which includes 9 European countries.

A system of four telescopes of 8.2 meters each, and four auxiliary telescopes of 1.8 meters each, is equivalent in aperture ratio to one device with a mirror diameter of 16.4 meters.

Each of the four telescopes can also work separately, receiving photographs that show stars up to the 30th magnitude. All telescopes rarely work at once, it is too expensive. More often, each of the large telescopes is paired with its 1.8 meter assistant. Each of the auxiliary telescopes can move along the rails relative to its "big brother", taking the most favorable position for observing this object. The Very Large Telescope is the most advanced astronomical system in the world. A lot of astronomical discoveries were made on it, for example, the world's first direct image of an exoplanet was obtained.

Space the Hubble telescope

The Hubble Space Telescope is a joint project of NASA and the European Space Agency, an automatic observatory in earth orbit, named after the American astronomer Edwin Hubble. The diameter of its mirror is only 2.4 m, which is smaller than the largest telescopes on Earth. But due to the lack of influence of the atmosphere, the resolution of the telescope is 7 - 10 times greater than a similar telescope located on Earth. "Hubble" owns many scientific discoveries: the collision of Jupiter with a comet, the image of the relief of Pluto, the auroras on Jupiter and Saturn ...

Hubble telescope in earth orbit

The first telescopes with a diameter of just over 20 mm and a modest magnification of less than 10x, which appeared at the beginning of the 17th century, made a real revolution in the knowledge of the cosmos around us. Today, astronomers are preparing to commission gigantic optical instruments thousands of times larger in diameter.

May 26, 2015 was a real holiday for astronomers around the world. On this day, Hawaii Governor David Egay authorized the start of the zero cycle of construction near the top of the extinct Mauna Kea volcano of a giant instrument complex, which in a few years will become one of the largest optical telescopes in the world.

The three largest telescopes of the first half of the 21st century will use different optical schemes. The TMT is built according to the Ritchey-Chrétien scheme with a concave primary mirror and a convex secondary one (both hyperbolic). The E-ELT has a concave primary mirror (elliptical) and a convex secondary mirror (hyperbolic). GMT uses Gregory's optical design with concave mirrors: primary (parabolic) and secondary (elliptical).

Giants in the arena

The new telescope is called the Thirty Meter Telescope (TMT) because its aperture (diameter) will be 30 m. If all goes according to plan, TMT will see the first light in 2022, and regular observations will begin another year later. The structure will be truly gigantic - 56 m high and 66 m wide. The main mirror will be composed of 492 hexagonal segments with a total area of ​​664 m². According to this indicator, TMT will surpass by 80% the Giant Magellan Telescope (GMT) with an aperture of 24.5 m, which in 2021 will come into operation at the Chilean Las Campanas Observatory, owned by the Carnegie Institution.

The 30-meter telescope TMT was built according to the Ritchey-Chrétien scheme, which is used in many currently operating large telescopes, including the currently largest Gran Telescopio Canarias with a main mirror with a diameter of 10.4 m. At the first stage, TMT will be equipped with three IR and optical spectrometers, and in the future it is planned to add several more scientific instruments to them.

However, the world champion TMT will not stay long. The opening of the European Extremely Large Telescope (E-ELT) with a record diameter of 39.3 m is scheduled for 2024, which will become the flagship instrument of the European Southern Observatory (ESO). Its construction has already begun at a three-kilometer altitude on Mount Cerro Armazones in Chile's Atacama Desert. The main mirror of this giant, composed of 798 segments, will collect light from an area of ​​978 m².

This magnificent triad will make up a group of next-generation optical supertelescopes that will have no competitors for a long time.

Anatomy of supertelescopes

The optical design of TMT goes back to a system that was proposed independently a hundred years ago by the American astronomer George Willis Ritchie and the Frenchman Henri Chrétien. It is based on a combination of a main concave mirror and a coaxial convex mirror of smaller diameter, both of which have the shape of a hyperboloid of revolution. Rays reflected from the secondary mirror are directed to the hole in the center of the main reflector and focused behind it. Using a second mirror in this position makes the telescope more compact and increases its focal length. This design has been implemented in many operating telescopes, in particular in the currently largest Gran Telescopio Canarias with a primary mirror 10.4 m in diameter, in the 10-meter twin telescopes of the Hawaiian Keck Observatory and in the four 8.2-meter telescopes of the Cerro Paranal Observatory, owned by ESO.

The optical system of E-ELT also contains a concave primary mirror and a convex secondary, but it has a number of unique features. It consists of five mirrors, and the main one is not a hyperboloid, as in TMT, but an ellipsoid.

GMT is designed completely differently. Its main mirror consists of seven identical monolithic mirrors with a diameter of 8.4 m (six make up a ring, the seventh is in the center). The secondary mirror is not a convex hyperboloid, as in the Ritchey-Chrétien scheme, but a concave ellipsoid located in front of the focus of the primary mirror. In the middle of the 17th century, such a configuration was proposed by the Scottish mathematician James Gregory, and was first implemented in practice by Robert Hooke in 1673. According to the Gregorian scheme, the Large Binocular Telescope (Large Binocular Telescope, LBT) was built at the International Observatory on Mount Graham in Arizona (both of its “eyes” are equipped with the same main mirrors as the GMT mirrors) and two identical Magellanic telescopes with an aperture of 6.5 m, which have been working at the Las Campanas Observatory since the early 2000s.

Strength is in the tools

Any telescope in itself is just a very large spotting scope. To turn it into an astronomical observatory, it must be equipped with highly sensitive spectrographs and video cameras.

TMT, which is designed for a service life of more than 50 years, will first of all be equipped with three measuring instruments mounted on a common platform - IRIS, IRMS and WFOS. IRIS (InfraRed Imaging Spectrometer) is a complex of a very high resolution video camera providing a field of view of 34 x 34 arc seconds and an infrared radiation spectrometer. IRMS is a multi-slit infrared spectrometer, while WFOS is a wide-angle spectrometer that can simultaneously track up to 200 objects in an area of ​​at least 25 square arc minutes. The design of the telescope includes a flat-rotating mirror that directs light to the devices you need at the moment, and it takes less than ten minutes to switch. In the future, the telescope will be equipped with four more spectrometers and a camera for observing exoplanets. According to current plans, one additional complex will be added every two and a half years. GMT and E-ELT will also have an extremely rich instrumentation.

Supergiant E-ELT will be the world's largest telescope with a 39.3 m primary mirror. It will be equipped with a state-of-the-art adaptive optics (AO) system with three deformable mirrors capable of eliminating distortions that occur at various heights and wavefront sensors for light analysis from three natural reference stars and four to six artificial ones (generated in the atmosphere using lasers). Thanks to this system, the resolution of the telescope in the near infrared zone in the optimal state of the atmosphere will reach six milliseconds of arc and will come close to the diffraction limit due to the wave nature of light.

European giant

The supertelescopes of the next decade will not come cheap. The exact amount is still unknown, but it is already clear that their total cost will exceed $ 3 billion. What will these gigantic tools give to the science of the Universe?

“The E-ELT will be used for astronomical observations on a wide range of scales, from the solar system to deep space. And on each scale scale, exceptionally rich information is expected from him, much of which other supertelescopes cannot give out, ”Johan Liske, a member of the scientific team of the European giant, who is engaged in extragalactic astronomy and observational cosmology, told Popular Mechanics. “There are two reasons for this: firstly, the E-ELT will be able to collect much more light than its competitors, and secondly, its resolution will be much higher. Take, say, extrasolar planets. Their list is growing rapidly, by the end of the first half of this year it contained about 2000 titles. Now the main task is not to multiply the number of discovered exoplanets, but to collect specific data about their nature. This is exactly what E-ELT will do. In particular, its spectroscopic equipment will make it possible to study the atmospheres of stony Earth-like planets with a completeness and accuracy that is completely inaccessible to currently operating telescopes. This research program provides for the search for water vapor, oxygen and organic molecules, which may be the waste products of terrestrial organisms. There is no doubt that E-ELT will increase the number of contenders for the role of habitable exoplanets.”

The new telescope also promises other breakthroughs in astronomy, astrophysics and cosmology. As is known, there are considerable grounds for the assumption that the Universe has been expanding for several billion years with an acceleration due to dark energy. The magnitude of this acceleration can be determined from changes in the dynamics of the redshift of light from distant galaxies. According to current estimates, this shift corresponds to 10 cm/s per decade. This value is extremely small for measurements with current telescopes, but for the E-ELT such a task is quite capable. Its ultra-sensitive spectrographs will also provide more reliable data to answer the question of whether the fundamental physical constants are constant or whether they change over time.

E-ELT promises a true revolution in extragalactic astronomy, which deals with objects located outside the Milky Way. Current telescopes make it possible to observe individual stars in nearby galaxies, but at long distances they fail. The European Super Telescope will provide an opportunity to see the brightest stars in galaxies millions and tens of millions of light years distant from the Sun. On the other hand, it will be able to receive light from the earliest galaxies, about which practically nothing is known yet. It will also be able to observe the stars near the supermassive black hole at the center of our Galaxy - not only to measure their speeds with an accuracy of 1 km / s, but also to discover now unknown stars in the immediate vicinity of the hole, where their orbital velocities approach 10% of the speed of light. . And this, as Johan Liske says, is far from a complete list of the unique capabilities of the telescope.

Magellan telescope

The giant Magellan telescope is being built by an international consortium that brings together more than a dozen different universities and research institutes in the United States, Australia and South Korea. Dennis Zaritsky, professor of astronomy at the University of Arizona and deputy director of the Stewart Observatory, explained to PM that Gregorian optics was chosen because it improves image quality over a wide field of view. In recent years, such an optical scheme has proven itself well on several optical telescopes in the 6–8 m range, and even earlier it was used on large radio telescopes.

Despite the fact that GMT is inferior to TMT and E-ELT in terms of diameter and, accordingly, the area of ​​the light-collecting surface, it has many serious advantages. Its equipment will be able to simultaneously measure the spectra of a large number of objects, which is extremely important for survey observations. In addition, GMT optics provide very high contrast and the ability to reach far into the infrared. The diameter of its field of view, like that of TMT, will be 20 arc minutes.

According to Professor Zaritsky, GMT will take its rightful place in the triad of future supertelescopes. For example, with its help it will be possible to obtain information about dark matter, the main component of many galaxies. Its distribution in space can be judged by the motion of the stars. However, most of the galaxies where it dominates contain relatively few stars, and rather dim ones at that. The GMT instrument will be able to track the movements of many more of these stars than any of the existing telescopes. Therefore, GMT will make it possible to more accurately map dark matter, and this, in turn, will make it possible to choose the most plausible model of its particles. Such a perspective acquires special value if one considers that, so far, dark matter has not been detected either by passive detection or obtained at an accelerator. Other research programs will also be carried out at GMT: the search for exoplanets, including terrestrial planets, the observation of the most ancient galaxies, and the study of interstellar matter.

On earth and in heaven

In October 2018, the James Webb Telescope (JWST) is scheduled to be launched into space. It will work only in the orange and red zones of the visible spectrum, but it will be able to observe almost the entire mid-infrared range up to wavelengths of 28 microns (infrared rays with wavelengths over 20 microns are almost completely absorbed in the lower atmosphere by carbon dioxide and water molecules). , so that ground-based telescopes do not notice them). Since it will be shielded from the thermal interference of the earth's atmosphere, its spectrometric instruments will be much more sensitive than ground-based spectrographs. However, the diameter of its main mirror is 6.5 m, and therefore, thanks to adaptive optics, the angular resolution of ground-based telescopes will be several times higher. So, according to Michael Bolte, observations at the JWST and ground-based supertelescopes will complement each other perfectly. As for the prospects for a 100-meter telescope, Professor Bolte is very cautious in his assessments: “In my opinion, in the next 20–25 years it will simply not be possible to create adaptive optics systems that can effectively work in tandem with a hundred-meter mirror. Perhaps this will happen somewhere in forty years, in the second half of the century.

Hawaiian project

"TMT is the only one of the three future supertelescopes to be located in the Northern Hemisphere," says Michael Bolte, a member of the board of directors of the Hawaiian project, professor of astronomy and astrophysics at the University of California at Santa Cruz. - However, it will be mounted not very far from the equator, at 19 degrees north latitude. Therefore, he, like other telescopes of the Mauna Kea observatory, will be able to survey the sky of both hemispheres, especially since in terms of observation conditions this observatory is one of the best places on the planet. In addition, TMT will work in conjunction with a group of nearby telescopes: the two 10-meter twins Keck I and Keck II (which can be considered the prototypes of TMT), as well as the 8-meter Subaru and Gemini-North. It is no coincidence that the Ritchey-Chrétien system is involved in the design of many large telescopes. It provides a good field of view and very effectively protects against both spherical and comatic aberration, which distorts images of objects that do not lie on the optical axis of the telescope. In addition, a truly magnificent adaptive optics is planned for TMT. It is clear that astronomers have good reason to expect that TMT observations will bring many remarkable discoveries.”

According to Professor Bolte, both TMT and other supertelescopes will contribute to the progress of astronomy and astrophysics, first of all, by once again pushing back the boundaries of the Universe known to science both in space and in time. Even 35–40 years ago, the observable space was mainly limited to objects no older than 6 billion years. It is now possible to reliably observe galaxies about 13 billion years old, whose light was emitted 700 million years after the Big Bang. There are candidates for galaxies with an age of 13.4 billion years, but this has not yet been confirmed. It can be expected that TMT instruments will be able to register light sources only slightly younger (by 100 million years) than the Universe itself.

TMT will provide astronomy and many other opportunities. The results that will be obtained on it will make it possible to clarify the dynamics of the chemical evolution of the Universe, to better understand the processes of formation of stars and planets, to deepen knowledge about the structure of our Galaxy and its nearest neighbors and, in particular, about the galactic halo. But the main thing is that TMT, like GMT and E-ELT, is likely to allow researchers to answer questions of fundamental importance that cannot now not only be correctly formulated, but even imagined. This, according to Michael Bolte, is the main value of supertelescope projects.

The Large Azimuth Telescope (LTA) of the Special Astrophysical Observatory (SAO) of the Russian Academy of Sciences is again observing celestial objects. In 2018, the observatory replaced the main element of the telescope - a mirror with a diameter of 6 m, but it turned out to be unsuitable for full-fledged work. The mirror of 1979 was returned to the telescope.

Smaller is better

BTA, located in the village of Nizhny Arkhyz in the mountains of Karachay-Cherkessia, is one of the largest in the world. The telescope was launched in 1975.

In 1960–1970, two mirrors were made for the BTA at the Lytkarino Optical Glass Plant (LZOS) near Moscow. Glass blanks with a thickness of about 1 m and a weight of about 70 tons were first cooled for two years, and then they were polished with diamond powder for another seven years. The first mirror worked on the telescope for four years. In 1979, due to surface imperfections, it was replaced.

In the 1990s, scientists raised the issue of a new mirror replacement. By that time, it had already repeatedly undergone re-aluminization procedures: about once every five years, the reflective layer of aluminum was washed off the mirror with acids, and then a new coating was applied. Each such procedure worsened the surface of the mirror at the micro level. This affected the quality of observations.

In the early 2000s, the Russian Academy of Sciences came to grips with this issue. Two options were proposed: repolishing the first BTA mirror and a radical upgrade of the telescope with the replacement of a 6-meter mirror with an 8-meter one.

In 2004, it was possible to buy in Germany a mirror blank of this size, made for the Very Large Telescope (VLT, Very Large Telescope) complex and not needed by it. An 8-meter mirror would provide a new level of vigilance and would return the Russian telescope to the top ten largest in the world.

However, this option also had disadvantages: high cost and high risks. Buying a blank would have cost €6-8 million, polishing would have cost about the same - it had to be done in Germany, because there is no equipment for mirrors of this diameter in Russia. It would be necessary to remake the upper part of the telescope structure and reconfigure all scientific equipment for the new luminosity.

“With the commissioning of an 8-meter mirror, only the dome of the telescope would have remained virtually untouched,” Dmitry Kudryavtsev, deputy director of the SAO, explained to Kommersant. “Now imagine all this in Russian realities with interruptions in funding for scientific projects. We could easily find ourselves in a situation where the telescope is literally taken to pieces, money does not come in, and we generally lose access to observations for an indefinite time.

It turned out as before

They didn’t even begin to calculate how much it would cost to redesign the telescope. “It was obvious that the Russian Academy of Sciences would not find such money,” Valery Vlasyuk, director of the SAO, told Kommersant. In 2004, the Academy decided to restore the first BTA mirror, which had been kept in a special container since 1979.

Photo: Kristina Kormilitsyna, Kommersant

The task was again entrusted to LZOS, which is now part of the Shvabe holding of the Rostec state corporation. To eliminate "congenital" defects from the surface of a mirror with an area of ​​28 sq. m, 8 mm of glass was cut, due to which its weight decreased by almost a ton. Polishing was planned to be carried out in three years, but due to interruptions in funding, it stretched for 10 years.

“The price increase is mainly explained by the financial crises that occurred between 2004 and 2018, and the subsequent inflation,” explains Vladimir Patrikeev, deputy head of the LZOS research and production complex. “For example, if in 2007 we brought a mirror from the Caucasus to the Moscow region for 3.5 million rubles, then in 2018 they were brought back already for 11 million rubles.

The restored mirror arrived in Nizhny Arkhyz in February 2018. about the transportation of a particularly fragile cargo weighing 42 tons, which took eight days.

Before being sent to the observatory, the restored mirror was certified for LZOS. However, after its installation in the standard frame of the BTA, significant deviations from the characteristics specified in the terms of reference were found.

Parabola started the process in a circle

“The quality of the mirror surface is evaluated by several parameters, the main of which are roughness and compliance with the parabolic shape,” says Mr. Kudryavtsev. “LZOS brilliantly coped with reducing the roughness of the mirror surface. If the second BTA mirror has 20 nanometers, then the restored one has only one nanometer. But there were problems with the shape of the mirror.

Based on the terms of reference, the standard deviation from the ideal paraboloid should have been no more than 95 nanometers. In reality, this parameter turned out to be at the level of 1 micron, which is ten times worse than the required value.

The problems with the restored mirror became clear almost immediately after its installation in the summer of 2018. Even then, it was decided to return the just replaced second mirror. But the observatory team was exhausted by the previous replacement, and besides, this multi-month procedure can only be carried out in the warm season.

BTA was put into operation with a low-quality mirror, if possible, the existing shortcomings were corrected with the help of mechanical systems. Due to the unstable and generally poor focusing on it, it was impossible to conduct photometric observations. Other scientific programs on the BTA were carried out, but with a loss of efficiency.

The return of the old mirror began on June 3, 2019. In September, test observations and the final adjustment of the telescope were carried out. Since October, BTA has returned to full-fledged work. 5 million rubles were spent on the operation.

“We are pleased with how the return of the old mirror went. It fits perfectly into the frame, the image quality is at the best level. For now, we will work like this, ”the director of the SAO RAS assured Kommersant.

Who is to blame and what to do

The joint commission of the SAO RAS, LZOS and NPO OPTIKA recognized the restored mirror as not complying with the terms of reference and in need of improvement. The formal reason is the lack of a stationary frame at the factory and computer modeling errors.

In Soviet times, the first mirror was polished in a real telescope frame, which was then transported from LZOS to the Caucasus and installed on the BTA. To polish the second mirror, a prototype frame was created at the factory - its simplified, cheap copy.

When in 2004 the Russian Academy of Sciences decided to restore the first mirror, the project involved the creation of a new frame imitation. The old one was scrapped in 2007.

And then there were problems with financing - there was no money to create a copy of the BTA frame. Then the experts decided that in the 21st century it is possible to polish a mirror not in a rigid frame, but with the help of computer simulation.

When performing control measurements, the mirror was supported by a steel tape. The resulting deformation of the glass was simulated, verified experimentally, and taken into account when adjusting the operation of the polishing machine. However, the inhomogeneity of the glass turned out to be much higher than the calculated one. In a regular frame, the restored mirror showed a deviation from the given shape by an order of magnitude worse than expected.

The commission recognized that the first mirror needed to be polished in imitation of the BTA frame. While it is stored in Nizhny Arkhyz. How much it will cost to repeat the process and whether it will be carried out again is still unknown. According to Vladimir Patrikeev, a representative of the plant, the decision to restore a copy of the frame at LZOS has not been made.

In the spent 250 million rubles. This included not only repolishing the mirror, says the director of the observatory, Valery Vlasyuk. The scope of work also included the transportation of the mirror for restoration and back to the BTA, the modernization of the polishing machine and the room temperature control system at LZOS, the repair of the BTA crane, which is used to rearrange the mirrors, the renovation of the technical premises of the telescope, and the creation of a mirror cooling system from scratch.

“All these improvements have remained with us and will reduce the cost of further work,” says Mr. Vlasyuk. “But so far the state has no money to continue work on the mirror. At the beginning of the 2000s, the SAO RAS wrote letters to all the powers that be, all the oligarchs, asking them to help update the BTA. And now we are also ready to ask the readers of Kommersant for help in order to still get a mirror with improved characteristics.

Julia Bychkova, Nizhny Arkhyz

B.M. Shustov, Doctor of Physical and Mathematical Sciences,
Institute of Astronomy RAS

Mankind has gathered the bulk of knowledge about the Universe using optical instruments - telescopes. Already the first telescope, invented by Galileo in 1610, made it possible to make great astronomical discoveries. Over the next centuries, astronomical technology was continuously improved and the modern level of optical astronomy is determined by the data obtained using instruments hundreds of times larger than the first telescopes.

The trend towards ever larger instruments has become particularly clear in recent decades. Telescopes with a mirror with a diameter of 8 - 10 m are becoming common in observational practice. Projects of 30-m and even 100-m telescopes are estimated as quite feasible already in 10 - 20 years.

Why are they being built

The need to build such telescopes is determined by tasks that require the ultimate sensitivity of instruments for detecting radiation from the faintest space objects. These tasks include:

• the origin of the universe;
• mechanisms of formation and evolution of stars, galaxies and planetary systems;
• physical properties of matter in extreme astrophysical conditions;
• astrophysical aspects of the origin and existence of life in the Universe.

To get the maximum information about an astronomical object, a modern telescope must have large area of ​​collecting optics and high efficiency of radiation receivers. Besides, Observation interference should be kept to a minimum..

At present, the efficiency of receivers in the optical range, understood as the fraction of detected photons from the total number of photons that arrived at the sensitive surface, is approaching the theoretical limit (100%), and further improvements are associated with increasing the format of receivers, speeding up signal processing, etc.

Observation interference is a very serious problem. In addition to natural disturbances (for example, cloudiness, dust formations in the atmosphere), the existence of optical astronomy as an observational science is threatened by increasing illumination from settlements, industrial centers, communications, and man-made pollution of the atmosphere. Modern observatories are built, of course, in places with a favorable astroclimate. There are very few such places on the globe, no more than a dozen. Unfortunately, there are no places with a very good astroclimate on the territory of Russia.

The only promising direction in the development of highly efficient astronomical technology is to increase the size of the collecting surfaces of instruments.

The largest telescopes: the experience of creation and use

In the last decade, more than a dozen projects of large telescopes have been implemented or are in the process of being developed and created in the world. Some projects provide for the construction of several telescopes at once with a mirror no less than 8 m in size. The cost of the instrument is determined primarily by the size of the optics. Centuries of practical experience in telescope construction have led to a simple way to compare the cost of a telescope S with a mirror with a diameter D (recall that all instruments with a primary mirror diameter greater than 1 m are reflecting telescopes). For telescopes with a solid primary mirror, as a rule, S is proportional to D 3 . Analyzing the table, you can see that this classic ratio for the largest instruments is violated. Such telescopes are cheaper and for them S is proportional to D a , where a does not exceed 2.

It is the amazing reduction in cost that makes it possible to consider projects of supergiant telescopes with a mirror diameter of tens and even hundreds of meters not as fantasies, but as quite real projects in the near future. We will talk about some of the most cost-effective projects. One of them, SALT, is being put into operation in 2005, the construction of giant telescopes of 30-meter class ELT and 100-meter - OWL has not yet begun, but they may appear in 10 - 20 years.

TELESCOPE	mirror diameter, m	Main mirror parameters	Location of the telescope	Project participants	Project cost, million $ USD	first light
KECKI KECK II		parabolic multi-segment active	Mauna Kea, Hawaii, USA	USA
VLT (four telescopes)		thin active	Chile	ESO, cooperation of nine European countries
GEMINI North GEMINI South		thin active	Mauna Kea, Hawaii, USA Cerro Pachon, Chile	USA (25%), England (25%), Canada (15%), Chile (5%), Argentina (2.5%), Brazil (2.5%)
SUBARU		thin active	Mauna Kea, Hawaii, USA	Japan
LBT (binocular)		cellular thick	Mt. Graham, Arizona, USA	USA, Italy
NO(Hobby&Eberly)	11 (actually 9.5)	spherical multi-segment	Mt. Fowlkes, Texac, USA	USA, Germany
MMT		cellular thick	Mt. Hopkins, Arizona, USA	USA
MAGELLAN two telescopes		cellular thick	Las Campanas, Chile	USA
BTA SAO RAS		thick	Mount Pastukhova, Karachay-Cherkessia	Russia
GTC		analogue of KECK II	La Palma , Canary Islands, Spain	Spain 51%
SALT		analogue NO	Sutherland, South Africa	Republic of South Africa
ELT	35 (actually 28)	analogue NO		USA	150-200 preliminary project
OWL		spherical multisegment mental		Germany, Sweden, Denmark, etc.	About 1000 avant-project

Large South African Telescope SALT

In the 1970s South Africa's main observatories were merged into the South African Astronomical Observatory. The headquarters is located in Cape Town. The main instruments - four telescopes (1.9-m, 1.0-m, 0.75-m and 0.5-m) - are located 370 km from the city inland, on a hill rising on the dry Karoo plateau ( Karoo).

South African Astronomical Observatory.
South African Large Telescope Tower
shown in section. In front of her are three main
operating telescopes. (1.9m, 1.0m and 0.75m).

In 1948, a 1.9-m telescope was built in South Africa, it was the largest instrument in the southern hemisphere. In the 90s. last century, the scientific community and the government of South Africa decided that South African astronomy could not remain competitive in the 21st century without a modern large telescope. Initially, a 4-m telescope, similar to the ESO NTT (New Technology Telescope) or more modern WIYN, at Kitt Peak Observatory was considered. However, in the end, the concept of a large telescope was chosen - an analogue of the Hobby-Eberly Telescope (HET) installed at the McDonald Observatory (USA). The project was named Large South African Telescope, in original - Southern African Large Telescope (SALT).

The cost of the project for a telescope of this class is very low - only 20 million US dollars. Moreover, the cost of the telescope itself is only half of this amount, the rest is the cost of the tower and infrastructure. Another 10 million dollars, according to modern estimates, will cost the maintenance of the tool for 10 years. Such a low cost is due to both the simplified design and the fact that it is created as an analogue of the already developed one.

SALT (respectively, HET) are radically different from previous projects of large optical (infrared) telescopes. The optical axis of SALT is set at a fixed angle of 35° to the zenith direction, and the telescope is able to rotate in azimuth for a full circle. During the observation session, the instrument remains stationary, and the tracking system, located in its upper part, provides tracking of the object in a 12° section along the altitude circle. Thus, the telescope makes it possible to observe objects in a ring 12° wide in the region of the sky that is 29 - 41° away from the zenith. The angle between the telescope axis and the zenith direction can be changed (no more than once every few years) by studying different regions of the sky.

The diameter of the main mirror is 11 m. However, its maximum area used for imaging or spectroscopy corresponds to a 9.2 m mirror. It consists of 91 hexagonal segments, each with a diameter of 1 m. All segments have a spherical surface, which greatly reduces the cost of their production. By the way, the blanks of the segments were made at the Lytkarino Optical Glass Plant, the primary processing was performed there, the final polishing is carried out (at the time of writing the article has not yet been completed) by Kodak. The Gregory corrector, which removes spherical aberration, is effective in the 4? region. Light can be transmitted via optical fibers to spectrographs of various resolutions in thermostatically controlled rooms. It is also possible to set a light instrument in direct focus.

The Hobby-Eberle telescope, and hence the SALT, are essentially designed as spectroscopic instruments for wavelengths in the 0.35-2.0 µm range. SALT is most competitive from a scientific point of view when observing astronomical objects that are evenly distributed across the sky or located in groups of several arc minutes in size. Since the telescope will operate in batch mode ( queue-scheduled), studies of variability during a day or more are especially effective. The range of tasks for such a telescope is very wide: studies of the chemical composition and evolution of the Milky Way and nearby galaxies, the study of objects with a high redshift, the evolution of gas in galaxies, the kinematics of gas, stars and planetary nebulae in distant galaxies, the search for and study of optical objects identified with x-ray sources. The SALT telescope is located on top of the South African Observatory telescopes, approximately 18 km east of the village of Sutherland ( Sutherland) at an altitude of 1758 m. Its coordinates are 20 ° 49 "East longitude and 32 ° 23" South latitude. The construction of the tower and infrastructure has already been completed. The journey by car from Cape Town takes approximately 4 hours. Sutherland is located far from all the main cities, so it has very clear and dark skies. Statistical studies of the results of preliminary observations, which have been carried out for more than 10 years, show that the proportion of photometric nights exceeds 50%, and spectroscopic nights average 75%. Since this large telescope is primarily optimized for spectroscopy, 75% is a perfectly acceptable figure.

The average atmospheric image quality measured by the Differential Motion Image Monitor (DIMM) was 0.9". This system is placed slightly above 1 m above the ground. Note that the optical image quality of SALT is 0.6". This is sufficient for work on spectroscopy.

ELT and GSMT Extremely Large Telescope Projects

In the USA, Canada and Sweden, several projects of class 30 telescopes are being developed at once - ELT, MAXAT, CELT, etc. There are at least six such projects. In my opinion, the most advanced of them are the American projects ELT and GSMT.

Project ELT (Extremely Large Telescope - Extremely Large Telescope) - a larger copy of the HET telescope (and SALT), will have an entrance pupil diameter of 28 m with a mirror diameter of 35 m. The telescope will achieve a penetrating power an order of magnitude higher than that of modern class 10 telescopes. The total cost of the project is estimated at about 100 million US dollars. It is being developed at the University of Texas (Austin), where experience has already been accumulated in building the HET telescope, the University of Pennsylvania and the McDonald Observatory. This is the most realistic project to implement no later than the middle of the next decade.

GSMT project (Giant Segmented Mirror Telescope - Giant Segmented Mirror Telescope) can be considered to some extent uniting the MAXAT (Maximum Aperture Telescope) and CELT (California Extremely Lerge Telescope) projects. The competitive way of developing and designing such expensive tools is extremely useful and is used in world practice. The final decision on GSMT has not yet been made.

The GSMT telescope is significantly more advanced than the ELT, and its cost will be about 700 million US dollars. This is much higher than that of the ELT due to the introduction aspherical main mirror, and the planned full turn

Stunningly Large OWL Telescope

The most ambitious project of the beginning of the XXI century. is, of course, a project OWL (OverWhelmingly Large Telescope - Stunningly Large Telescope) . OWL is being designed by the European Southern Observatory as an alt-azimuth telescope with a segmented spherical primary and flat secondary mirrors. To correct spherical aberration, a 4-element corrector with a diameter of about 8 m is introduced. When creating OWL, technologies already developed in modern projects are used: active optics (as on NTT, VLT, Subaru, Gemini telescopes), which makes it possible to obtain an image of optimal quality; primary mirror segmentation (as on Keck, HET, GTC, SALT), low cost designs (as on HET and SALT), and multi-stage adaptive optics being developed ( "Earth and Universe", 2004, No. 1).

The Astonishingly Large Telescope (OWL) is being designed by the European Southern Observatory. Its main characteristics are: the diameter of the entrance pupil is 100 m, the area of ​​the collecting surface is over 6000 sq. m, multi-stage adaptive optics system, diffraction image quality for the visible part of the spectrum - in the field 30", for the near infrared - in the field 2"; the field limited by the image quality allowed by the atmosphere (seeing) is 10"; the relative aperture is f/8; the working spectral range is 0.32-2 microns. The telescope will weigh 12.5 thousand tons.

It should be noted that this telescope will have a huge working field (hundreds of billions of ordinary pixels!). How many powerful receivers can be placed on this telescope!

The concept of gradual commissioning of OWL has been adopted. It is proposed to start using the telescope as early as 3 years before the filling of the primary mirror. The plan is to fill the 60 m aperture by 2012 (if funding opens in 2006). The cost of the project is no more than 1 billion euros (the latest estimate is 905 million euros).

Russian perspectives

About 30 years ago, a 6-m telescope was built and put into operation in the USSR BTA (Large Azimuth Telescope) . For many years it remained the largest in the world and, of course, was the pride of Russian science. BTA demonstrated a number of original technical solutions (for example, alt-azimuth installation with computer guidance), which later became the world technical standard. BTA is still a powerful tool (especially for spectroscopic studies), but at the beginning of the XXI century. it has already found itself only in the second ten largest telescopes in the world. In addition, the gradual degradation of the mirror (now its quality has deteriorated by 30% compared to the original) removes it from the list of effective tools.

With the collapse of the USSR, BTA remained practically the only major instrument available to Russian researchers. All observation bases with moderate-sized telescopes in the Caucasus and Central Asia have significantly lost their significance as regular observatories due to a number of geopolitical and economic reasons. Work has now begun to restore ties and structures, but the historical prospects for this process are vague, and in any case, it will take many years only to partially restore what was lost.

Of course, the development of the fleet of large telescopes in the world provides an opportunity for Russian observers to work in the so-called guest mode. The choice of such a passive path would invariably mean that Russian astronomy would always play only secondary (dependent) roles, and the lack of a base for domestic technological developments would lead to a deepening lag, and not only in astronomy. The way out is obvious - a radical modernization of BTA, as well as full-fledged participation in international projects.

The cost of large astronomical instruments, as a rule, amounts to tens and even hundreds of millions of dollars. Such projects, with the exception of a few national projects carried out by the richest countries in the world, can only be implemented on the basis of international cooperation.

Opportunities for cooperation in the construction of class 10 telescopes appeared at the end of the last century, but the lack of funding, or rather the state interest in the development of domestic science, led to the fact that they were lost. A few years ago, Russia received an offer to become a partner in the construction of a major astrophysical instrument - the Great Canary Telescope (GTC) and the even more financially attractive SALT project. Unfortunately, these telescopes are being built without the participation of Russia.

On Tuesday we started testing the new instrument on our Zeiss-1000 telescope. The second largest optical telescope of our observatory (colloquially known as "meter") is much less known than the 6-meter BTA and is lost against the background of its tower. But despite the relatively modest diameter, this is a rather sought-after tool, actively used by both our astronomers and external applicants. A lot of time is devoted to monitoring - tracking changes in the brightness and spectrum of variable objects: active galactic nuclei, sources of gamma-ray bursts, binary systems with white dwarfs, neutron stars, black holes, and other flaring objects. Recently, transits of extrasolar planets have also been added to the list.
In ancient times, when we did not yet observe remotely, coming into the room on the BTA tower in the morning, sometimes we took the traditional "tired picture from the BTA" - dawn over the neat Zeiss-1000 tower. Something like this, when the clouds lie down to the horizon and merge with snow, if it's winter:

Before that, I had to work on the meter myself only a few times and a very long time ago, in particular, I received data for my first publication on it (photometry of the dusty galaxy NGC972).

A small photo story about places where tourists do not often visit.

Telescope in a rare configuration - the Cassegrain focus is free of equipment:

I take the opportunity to take a photo of my own reflection in the secondary mirror:

I go out to the area around the dome and take a picture of the telescope through the open visor. Note the wood paneling of the dome. The telescope was supplied from the GDR complete with the building:

On the other side, there are all-sky cameras on the roof, the picture from which is broadcast to the network. Below - the valley of the Bolshoy Zelenchuk River:

To the right - the dome of our third telescope, the smallest - "Zeiss-600". The moon rises next to Elbrus.

Both close-ups:

Panorama of the BTA tower complex with a megacrane, the sun sets somewhere above