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Berdnikov L.N.,Sternberg Astronomical Institute of Moscow University | Turner D.G.,Saint Marys University, Halifax
Astronomy Reports | Year: 2010

We obtained 380 photographic brightness estimates for the long-period classical Cepheid II Car (P = 64.4 days) from the plate stacks of the Harvard College Observatory. Combined with the published photoelectric and CCD observations, these data enable the construction of an O-C diagram covering 120 years. The O-C diagram is parabolic, making it possible for the first time to determine the quadratic light-curve elements and calculate the evolutionary rate of increase of the period, dP/dt = 719(±15) s/year (log(Ṗ/P) = -4.64), in agreement with theoretical computations for the third crossing of the instability strip. The available data, reduced using the method described by Eddington and Plakidis, demonstrate the presence of small random period fluctuations that do not distort the evolutionary changes of the O-C residuals. © Pleiades Publishing, Ltd., 2010.

Artamonov B.P.,Sternberg Astronomical Institute of Moscow University | Bruevich V.V.,Sternberg Astronomical Institute of Moscow University | Gusev A.S.,Sternberg Astronomical Institute of Moscow University | Ezhkova O.V.,Sternberg Astronomical Institute of Moscow University | And 5 more authors.
Astronomy Reports | Year: 2010

We have determined the realistic seeing of the 1.5-m AZT-22 telescope of the Mt. Maidanak Observatory (Astronomical Institute, Uzbek Academy of Sciences) using more than 20 000 CCD frames with stellar images in the UBV RI bands acquired in 1996-2005: ε = 1.065″ in the V band. The characteristic seeing reduced to unit air mass, εmed V(M(z) = 1), is 0.945″. We derived color equations for the CCD detectors used with the telescope. Atmospheric-extinction coefficients in different photometric bands were also determined. The mean V -band atmospheric extinction is 0.20m ± 0.=04m. The time needed for the conditions to settle, in the free atmosphere as well as inside the telescope dome, is 2-2.5 hours after the end of astronomical twilight. For nights with εmed V > 0.9″, we find a persistent difference between the seeing found at this telescope and measured simultaneously with a differential image motion monitor, amounting to ~0.1m. © 2010 Pleiades Publishing, Ltd.

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