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Corrections to the Hipparcos Proper Motions in Declination for 807 Stars
We used the data on latitude variations obtained from observations with10 classical photographic zenith tubes (PZT) in order to improve theHipparcos proper motions in declinations ?_{?} for 807 stars.Part of observing programmes, carried out during the last century forthe purpose of studying the Earth's rotation, were realized by using PZTinstruments. These observations were performed within in the intervals(tens of years) much longer than that of the Hipparcos mission (lessthan 4 years). In addition, the annual number of observations for everyPZT-programme star is several hundreds on the average. Though theaccuracy of the star coordinates in the Hipparcos Catalogue is by twoorders of magnitude better than that of the star coordinates from thePZT observations, the large number of observations performed a muchlonger time interval makes it possible to correct the Hipparcos propermotions and to improve their accuracy with respect to the accuracy givenin the Hipparcos Catalogue. Long term examinations of latitude and timevariations were used to form the Earth Orientation Catalogue (EOC-2),aimed at a more accurate determination of positions and proper motionsfor the stars included. Our method of calculating the corrections of theproper motions in declination from the latitude variations is differentfrom the method used in obtaining the EOC-2 Catalogue. Comparing theresults we have established a good agreement between our ?_{?}and the EOC-2 ones for the star sample used in the present paper.
| Pulkovo compilation of radial velocities for 35495 stars in a common system.
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| Kinematics of Sandage-Fouts stars in three cardinal directions
V and (B - V) for 429, 442, and 427 stars are observed in the directionsof the anticenter, Cygnus, and the NGP, respectively, and DDO colors forthose stars G0 and later. The samples observed are ones for whichSandage and Fouts (1987) have published radial velocities. W, V, and Wcomponents of space velocity are derived from DDO distances withavailable proper motions. A clear correlation was found to exist betweenthe velocity dispersions and Fe/H with the dispersions decreasing asFe/H increases to about + 0.00, where V then becomes significantlynegative. The 'thick disk' component is clearly recognized, with sigma(W) approximately equal to 36 km/sec. In the 'old thin disk' and the'young thin disk', 43 percent and 42 percent of the stars have negativeV values, respectively.
| U, V, W velocity components for the old disk using radial velocities of 1295 stars in the three cardinal Galactic directions
New radial velocities are presented for 1295 stars chosen at random nearthe three cardinal Galactic directions of l = 180 deg, b = 0; l = 90deg, b = 0 deg; and b = 90 deg, giving the distribution in U, V, and W,respectively, from the radial velocities alone. The measurements weremade with the coude spectrograph of the Mount Wilson 100 in. Hookerreflector. The purpose of the program is to set limits on the densitynormalization in the solar neighborhood of the old thin disk, the oldthick disk, and the halo. Many more high-velocity stars are present inthe unbiased sample than expected from previous estimates of thenormalization. The data suggest the density ratios in the solarneighborhood to be about 90 percent, 10 percent, and about 0.5 percentfor the thin disk, thick disk, and halo populations, respectively.
| Mean positions and proper motions of 305 stars obtained from the combination of PZT observations at Ondrejov with AGK positions
Observations of 305 stars carried out at the Ondrejov Observatory in theperiod 1973-1983 were compared to the positions of the same stars in theAGK 2 and AGK 3 catalogs in order to obtain their mean positions andproper motions. The observations were performed in the course of 1140nights using the PZT telescope and comprise more than 32 thousand startransits. The average mean errors in the right ascension and declinationof a star that was observed thoughout the whole period were + or -0.0019 s and + or - 0.019 arcsec in the epoch around 1979. It ispredicted that the errors will increase + or - 0.0055 sec and + or -0.059 arcsec in the year 2000. A table listing the errors in the rightascension and declination is provided.
| The determination of mean positions and proper motions of 304 stars from PZT observations at Ondrejov
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Membre dels grups següents:
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Dades d'Observació i Astrometria
| Constel·lació: | Cygnus |
| Ascensió Recta: | 20h59m54.74s |
| Declinació: | +50°03'46.9" |
| Magnitud Aparent: | 9.062 |
| Moviment propi RA: | 26.5 |
| Moviment propi Dec: | 16.3 |
| B-T magnitude: | 9.51 |
| V-T magnitude: | 9.099 |
Catàlegs i designacions:
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