Kinematic Control of the Inertiality of the System of Tycho-2 and UCAC2 Stellar Proper Motions

Based on the Ogorodnikov-Milne model, we analyze the proper motions of Tycho-2 and UCAC2 stars. We have established that the model component that describes the rotation of all stars under consideration around the Galactic y axis differs significantly from zero at various magnitudes. We interpret this rotation found using the most distant stars as a residual rotation of the ICRS/Tycho-2 system relative to the inertial reference frame. For the most distant ($d\approx900$ pc) Tycho-2 and UCAC2 stars, the mean rotation around the Galactic y axis has been found to be $M_{13}=-0.37\pm0.04$ mas yr$^{-1}$. The proper motions of UCAC2 stars with magnitudes in the range $12-15^m$ are shown to be distorted appreciably by the magnitude equation in $\mu_\alpha\cos\delta$, which has the strongest effect for northern-sky stars with a coefficient of $-0.60\pm0.05$ mas yr$^{-1}$ mag$^{-1}$. We have detected no significant effect of the magnitude equation in the proper motions of UCAC2 stars brighter than $\approx11^m$.Comment: 15 pages, 6 figure

The Pul-3 catalogue of 58483 stars in the Tycho-2 system

A catalogue of positions and proper motions of 58483 stars (Pul-3) has been constructed at the Pulkovo observatory. The Pul-3 is based on the results of measurements of photographic plates with galaxies (Deutsch's plan). All plates were taken using the Pulkovo Normal Astrograph (the first epoch is in the 1950s and the second epoch is in the 1970s).
The Pul-3 catalogue contains stars of mainly 12 to 16.5 mag in 146 fields with galaxies in the declination zone from $-5^\circ$ to $+85^\circ$. The Tycho-2 has been used as a reference catalogue.
The mean epoch of the Pul-3 is 1963.25. The internal positional accuracy of the Pul-3 catalogue at the mean epoch of observations is ±80 mas. The accuracy of the proper motions is mostly within ±3 mas/yr to ±12 mas/yr. Comparisons of the Pul-3 with Tycho-2 and ARIHIP have been done at the mean epoch of the Pul-3. The Pul-3 external positional accuracy relative to Tycho-2 is ±150 mas

Exploration of the Solar System : projection of the past into the future

International audienc

Exploration of the Solar System : projection of the past into the future

International audienc

Exploration of the Solar System : projection of the past into the future

International audienc

Astrometric results of observations at Russian observatories of mutual occultations and eclipses of Jupiter's Galilean satellites in 2009

International audienceIn 2009, in five Russian observatories photometric observations of Jupiter's Galilean satellites during their mutual occultations and eclipses were carried out. Based on these observations, an original method was used to ascertain astrometric results such as the difference between the coordinates of pairs of satellites. Fifty-three phenomena were successfully observed. A total of 94 light curves of satellites were measured. The error in the coordinates of satellites due to random errors in photometry, calculated on all data obtained, was 0.041" in right ascension and 0.046" in declination. The discrepancies between the theory and observations in these coordinates was found to be 0.060" and 0.057", respectively. The results were uploaded to the common database for all observations of natural satellites of planets at the Natural Satellites Data Center (NSDC), which is available online at http://www.sai.msu.ru/neb/nss/index.htm . For the first time in the practice of photometric observations of satellites in epochs of mutual occultations and eclipses a new method of observation was tested, which eliminates from astrometric results the major systematic errors caused by an inaccurate account of the background level. The tests were conducted in the Terskol Observatory and the observatory of the Crimean laboratory of the Sternberg State Astronomical Institute of the Moscow State University. The application of the new method showed that the elimination of the background level at these observatories was carried out correctly