History of Observatory

Vilnius University Observatory, Vilnius University

1753-1940. The Vilnius University Observatory is one of the oldest astronomical institutions in Europe. Since its foundation in 1753 the Observatory possessed dozens of telescopes of different sizes and assignments. Some of them survived and are exhibited in the Science Museum in Vilnius University. Among them is one of the three Schwerd photometric telescopes manufactured in Germany in 1868. This telescope was used for visual photometry of stars in the seventies of the 18th century. A new generation of the photometric telescopes appeared in Lithuania in the twenties of this century. These were Carl Zeiss telescopes of 13-15 cm diameters used for photographic photometry of variable star fields. In 1938 the Vilnius Observatory obtained a 48 cm reflecting telescope and the Kaunas Observatory bought a 63 cm mirror. Both these instruments started to operate only in 1960 and 1973, respectively, and both were used for photoelectric stellar photometry. These telescopes have been used for observations in the Vilnius seven-colour photometric system, which was established for photometric three-dimensional classification of stars in the conditions of interstellar reddening.

Read more: Kilmka L. (2003BaltA..12..649K).

Molėtai Astronomical Observatory, Institute of Theoretical Physics and Astronomy

In 1962, the Department of Astrophysics was established at the Institute of Physics. In 1969, the first dome was built on Kaldiniai Hill (E 25 deg 33' 48.0" N 55 deg 18' 57.5"), near the town of Moletai. The first 25 cm diameter telescope of the Moletai Astronomical Observatory was mounted. The 63 cm telescope was one of the first instruments installed at the new Moletai Observatory in 1973, it was built using the same 63 cm mirror that Kaunas Observatory obtained in 1938. For photometric observations of faint stars the Vilnius astronomers needed telescopes of larger sizes. In 1978 we succeeded to buy a reflecting 1 meter telescope of the Ritchey-Chretien type made by Carl Zeiss, Jena. This telescope was installed at our observing station on Mount Maidanak in Uzbekistan (2500 m altitude) and so far it is our main photometric instrument situated in excellent astroclimatic conditions. At the same time, inspired by Harold Johnson's ideas about the cheap photometric telescopes of moderate size, we started designing a telescope of 1.5 m class for photometric purposes. Soon our efforts were joined by a group of constructors of the Astronomical Observatory of Leningrad (now St. Petersburg) University. This group, leaded by director of the Observatory M.K. Babadzhaniants, has succeeded in organizing an optical and mechanical shop capable to produce telescopes of diameters up to 2 meters and even larger. Our telescope of 165 cm diameter was the first product of this shop. The telescope was mounted at the Moletai Observatory in 1990. Its mounting is of the English type and the dome is of 12 m diameter at 20 m height above the ground. The main mirror of 165 cm diameter and f/3 aperture ratio is made from sital (zerodur) material at the Lytkarino optical factory near Moscow. The secondary mirror is made from fused quartz. Both mirrors form a Ritchey-Chretien system of f/12 aperture ratio. The focal length of the telescope is 1968 cm. Stellar image sizes investigated in the factory conditions are claimed to be of the order of 1", which is less than the atmospheric seeing typical in Lithuania (2" — 3"). The telescope is moved by step engines and was operated by a Soviet-made computer DVK-2 which, unfortunately, was oldfashioned and later was replaced by an IBM one. The instrumentation available on our 165 cm telescope included an automatic stellar photometer, a diffraction slit spectrograph UAGS from Carl Zeiss Jena and a Kron-type electronographic camera. The seven-channel photometer used a filter wheel with different versions of action: from changing filters with given exposures to permanent rotation with a speed of one revolution per second. This last version made possible quasi-simultaneous photometry of a star in all seven filters, which was important for measurements of exact stellar colours in the conditions of unstable atmospheric transparency.

Our experience with the Vilnius photometric system (Straižys, 1992msp..book.....S) realized with a CCD detector on the 90 cm telescope of the Kitt Peak National Observatory showed that the accurate photometry (with o of the order of ±0.02 mag) can be obtained for stars down to 17 mag (Boyle et al., 1990A&AS...84....1B, 1990A&AS...86..395B; Smriglio et al., 1991A&AS...88...87S; Straižys, 1992BaltA...1..107S), if the total exposure time for all 7 filters is of the order of 1 hour. With our 165 cm telescope we reached 18 mag at similar exposure times. This made it possible to obtain two- or three-dimensional classification of such faint stars in spectral types, luminosities and metallicities. The microchannel detector was manufactured at the Institute of Physics (Vilnius) and was ready later in 1992. Its main drawback is low counting rate (105 sec-1), which restricts its use to stars fainter than ti 14 mag.

Nowerdays we operate three telescopes: 35/51 cm Maksutov, 63 cm Cassegrain and 165 cm Richey - Chrétien and a number of instruments: two CCD photometers, coravel-type radial velocity spectrometer and high-resolution spectrograph. The infrastructure of 165 cm Richey - Chrétien was reconstructed in 2014. Both Richey - Chrétien and Maksutov now are generaly operated remotely.