Absolute declination determinations with the Pulkovo Photographic Vertical Circle

Abstract

The Pulkovo photographic vertical circle(PVC) designed and constructed under the supervision of Prof.Dr.M.S.Zverev (1) at the Pulkovo Observatory is used at present for determination of absolute declinations of bright and faint fundamental stars after its reconstruction and modernisation (2, 3). The main optical system of the PVC is the Maksutov meniscus cassegrain system (D = 200mm, f’ = 2000mm) with a photographic micrometer for star registrations. The limiting magnitude of ORWO NP - 27 plates is m=8.5 for zenith A special measuring machine is used for automatic measurements of star plates of the PVC (4-6). The Pulkovo PVC is equipped with two glass-circles with 4 photoelectric scanning microscopes for each circle. A description of the photoelectric reading system of the PVC is given in (7). The investigation shows that the mse of a single reading of one microscope is about + 005 (7). Observations of about 200 FK4 stars made in 1974-1977 show that the PVC instrumental system is sufficiently stable and ensures high precision as far as accidental errors are concerned. The mse of a single observation is δo= ± 018 at the zenith and no more than ± 030 at z = 50° (3) A special analysis of the observations made by the PVC showed the presence of chromatic refraction effects, particularly, at great zenith distances (8). The early type stars (0, B, A) are most affected by chromatic refraction. The refraction effects are northwards and southwards asymmetric relative to the zenith.