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.