Butenko G. Investigation of a Two-Metre Telescope for Increase of Astrophysical Observation Quality

Using the Gartmann method, we investigated the state of the Ritchey-Chretien and coude optical system fоr the two-metre telescope at the Terskol Peak Observatory as well as some factors affecting the quality of an image created by telescope optics. From special observations made during 1998-2004, we derived values for Zeidel aberration (coma, spherical aberration and astigmatism) for the field centre and through the Ritchey-Chretien optical system field, values of scattering circles with the Ritchey-Chretien and coude systems, estimated the state of the Ritchey-Chretien system adjustment and operation of fasteners and mirror off-loading systems. A series of CCD observations of a sky area in the NGC 6913 cluster was made with the 2-m telescope to realize the UBVR Johnson system. We derived magnitudes and positions for stars down to V = 20m for a sky area of 8'x5'. The instrumental photometric system is determined with respect to the UBVR Johnson system. The rms error is 0.02-0.03m for magnitude determination and 0.03-0.04" for position determination. On the basis of our results of the investigation of the seeing of the tube and dome of the two-metre telescope, we substantiated the use of ventilation systems of the building under dome and of close telescope tube as worked through operating conditions.