Shu-He Wang

Removal of tracking error with image restoration

In this paper, image restoration is presented as a way to remove the influence of tracking error in astrometric CCD images, based on the characteristics of spatially invariant tracking error within a CCD frame. The direct deconvolution method was used in the process of image restoration. The results of reduction using practical data show improved precision in the images of star centers, including those of closely spaced stars. In particular, close binaries can be separated easily after image restoration.

Proper motions of Hipparcos stars in two plate areas

Abstract Using the ACT reference catalogue as preliminary reference we have reduced 31 exposures on 15 plates in two areas taken with the 40-cm refractor of our Observatory. Using the central overlapping technique and an iterative procedure we have derived high-precision positions and proper motions for 54 stars, including 16 Hipparcos stars. For the latter, the mean standard errors, in right ascension and declination, are 0.70 and 0.59 mas/yr in proper motion, and 10.5 and 7.5 mas in position.

CCD astrometric observations of faint satellites and update of their orbits

This paper reports on our observing campaign of faint satellites performed at the National Time Service Center and Sheshan station of SHAO from 1994 up to today. In the past few years due to benefit from using a large size CCD and the publication of the modern catalogues (UCAC2), a series of observations of faint satellites were obtained by us. Moreover the work of improving the orbit of Phoebe via numerical fit to the observations over a century is also presented.

“Proper Motions” of optical counterparts of extragalactic radio sources and the precession constant☆

Abstract We use optical observations over long time spans of optical counter-parts of radio sources to discuss again the value of the constant of precession. Because the present value is not accurate, we first reduce all the observational results made at different epochs to the common reference system J 2000.0, and their separate reference star catalogues to the FK5 system, then we can obtain the so-called “proper motion” of the stars in the FK5 system. From the “proper motions” so obtained we can estimate the correction to the precession constant. Separate estimates, made here for 44 and 25 sources, are −2.67 ± 1.33 mas/yr, and −3.31 ± 1.63 mas/yr. We compared these values with the results from new techniques and found a good agreement between them.

Observations of the collision of Comet SL9 with Jupiter

Abstract Six impacts were observed with the 1.5m telescope and a CCD at Shanghai Observatory Sheshan Station. We give a light curve of the flash on Europa caused by the impact of fragment K12 and four post-collision photographs of Jupiter.

“Proper Motions” of Extragalactic Sources and the Precession Constant

From the observational catalogues of the extragalatic sources,the common sources with larger observational intervals are selected. After a reduction of optical catalogue systems to the FK5, the “proper motions” of these sources are obtained in the FK5 system. With these values the correction of the precession constant has been estimated and compared with that obtained from the new techniques