International Center for Astronomical, Medical and Ecological Research
 Large Horizontal Solar Telescope

Terskol Peak is a spur of Elbrus mountain. It has altitude 3100 m and coordinates 4313'N, 2h50mE. The ATsU-26 telescope was established there in 1989. The telescope is equipped with 5-camera spectrograph, thus it allows simultaneous observations in five spectral regions. Diameter of the main spherical mirror is 650 mm, focal length - 17750 mm; diameter of the collimator and cameras - 300 mm, focal length - 8000 mm; grating - (250*200) mm, 600 lines/mm; dispersion in fourth order - 21.9 mm/nm at 395.0 nm, 33.0 mm/nm at 650.0 nm. The telescope scheme is shown on the right figure.

The telescope was used mainly for photografic observations of solar flares in early 90-th. Then its exploitation was practically stalled. Since 1997 it was under a reconstruction. A lot of work was done to repair the building and to fix problems with the spectrograph. The reconstruction was finished in autumn of 2000. Now the typical instrumental profile of the spectrograph has 18 mA width at half intensity (instead of 40 mA before the reconstruction), it was obtained in fourth spectral order with help of He-Ne laser (630 nm). The spectrograph is also pretty stable - shifts of the laser line don't exceed 6 mA (in past the shifts exceed 12 mA). Similar results concerning stability were obtained with Ne emission lamp. So, these results are confident. The scattered light was measured with observing saturated oxygen lines near 763 nm, it equals 3%. Such a high level of scattered light is mainly because of baffles absence. That will be corrected soon. Below, several figures with results of the spectrograph tests are placed.

At the upper panel instrumental profiles of the spectrograph before (dashed line) and after (solid line) the reconstruction are drawn. At the lower panel a registration of saturated telluric oxygen lines near 763  nm is drawn. It shows the scattered light level (3%) in the spectrograph.


At the upper and middle panels shifts of the laser line with time before and after reconstruction are drawn. It is easy to see that stability of the spectrograph was improved by two times. At the lower panel shifts of the telluric line marked with dot at the lower panel of the left figure are drawn. These observations was made in the same day with observations presented at the middle panel. It is possible to conclude that telluric lines are not good wavelength repers.

Telescopes & Equipment
 2m RCC Telescope produced by Carl Zeiss Jena GmbH (Germany)
 Large Horizontal Solar Telescope  
 Zeiss-600 Telescope
 MAtrix Echelle SpecTROgraph
  MMCS -
 Multi Mode Cassegrain
 Terskol Ultra Violet Echelle Spectrometer
Some of the Observatory Activities
 Spectral investigations of interstellar clouds, solar analogs, X-ray binary stars, etc.
 Orbit calculation and monitoring of geosynchronous satellites
 Simultaneous observations with the Synchronous Network of Optical Telescopes to study microvariability of stars
  Study of gas and dust in comets
  Atmospheric studies