Operation and Development of the Perek 2-m Telescope





The main task of this group led by Miroslav Šlechta concerns maintenance and upgrading of the Perek 2‑m telescope in Ondřejov. The Ondřejov 2-m telescope is the largest optical instrument for stellar and since recently also for exoplanetary research in the Czech Republic. The telescope is equipped with single order and echelle spectrographs, both placed in the coudé focus. The telescope has been in operation since 1967 and has become a national instrument for astrophysical research.

The group is a team of technicians, mechanicians, electricians and software engineers. It consists of non-scientific technical staff whose primary responsibility is to ensure the telescope functions. The group provides technical support and it maintains and further develops the telescope and its instruments (spectrographs and photometric camera). Members of the group also work as observers during each observational night.


MEMBERS OF THE GROUP


Upgrades of the telescope

In the past, two major improvements of the telescopes were successfully performed. In 2007, modernization of the driving electronics was performed. This included the replacement of the position sensors and the driving software. The original electronics that were unique and hence irreplaceable were replaced with standard commercial electronics. In 2009 all the telescope mirrors were recoated, which significantly improved the telescope performance.

The most significant and fundamental upgrade of the telescope during last decades was performed by the group in 2019. The optical configuration was completely changed, which led to an increased efficiency of the optical system. Previously, the light was reflected to the coudé spectrographs with a system of mirrors. However, the reflecting surfaces slowly degrade with time that leads to an exponential decrease of the total efficiency. It is now possible to observe even very faint objects. The main part of the upgrade was putting the optical fibers from the primary focus to the coudé rooms, where the spectrographs are placed. As a result, only one reflecting surface (i.e., the 2‑m primary mirror) is present instead of four mirrors, which was before. With this upgrade of the telescope, higher efficiency and extension of the observational limits were achieved. The possibility of observing fainter objects broaden the number of observing programs which can be performed with the Perek 2‑m telescope. This modernization opens new horizons and offers Czech astronomers a device that will stand up on an international scale.

Besides the upgrade of the optics of spectrographs, in addition, the field of view in the primary focus is used and a photometric Mark2 3200 camera (Moravian Instrument) for direct imaging is installed there now. Currently, the photometric camera is equipped with u, g, r, i, and z collar filters corresponding to Sloan sky survey.


Usage of the telescope

The telescope is regularly used for scientific observations. Most observations are performed by scientists from the Astronomical Institute (members of the working group Physics of Hot Stars and Extrasolar Planet Research), however, colleagues from other institutes and universities also use this equipment (Charles University Prague, Masaryk University Brno, University of Wrocław, Astronomical Institute Tatranská Lomnica). The telescope is also used in international spectroscopic campaigns. The 2-m telescope with its spectrographs also serves as an educational instrument for students from two major Czech universities (Faculty of mathematics and physics, Charles University Praha and Faculty of Science, Masaryk University Brno), and also for students from abroad (Institte of Physics and Astronomy, Potsdam University, Germany; Faculty of Mathematics, University of Belgrade, Serbia).

Observing conditions in Ondřejov

The observing conditions are given by the location of Ondřejov in the middle Europe. The typical seeing is about 3 arcseconds and only rarely falls below 2 arcseconds. The distribution of clear nights can be seenin Fig. 1. The winter months are usually very poor regarding the observing nights, while March-April and June-September are the months with the highest percentage of usable observing time.

Fig. 1. The typical yearly distribution of observing hours from 2015. The grey-shaded columns show the total amount of hours when the Sun is 12 degress below the horizon, the coloured columns and corresponding numbers in yellow show the number of usable observing hours, the numbers in the pink boxes show the percentage of usable observing hours. Figure from Kabáth et al., 2020, PASP, 132, 1009.