The influence of solar mass-loss on the planetary orbital elements in the high order solution, based on the previous work, is discussed.The numerical results for the influence of 2-3 order solution on the planetary orbital elements are calculated.The theoretical results show that in the third order solution the solar mass-loss will introduce the secular, mixed and periodic terms continually in the semimajor axis but only the periodic term produces in the eccentricity and the argument of perihelior of planetary orbits.Although the numerical effects are very less in the 2-3 order solution, but there is a qualitative meaning for the study of the stability of solar system.

We take the duration as the optimal period during which the more and better observational data are available within one year. After statistical analyzing the related spectral data obtained with the spectrograph from 1976 to 1987, an annual distribution of optimal duration of solar spectral observation at the Phoenix Mountain of Yunnan Observatory is preliminary obtained, the result shows that the optimal durations in a year are September, then, from March to April.

The structure and the functions of the high-speed FX correlator of Chinese VLBI network are described, and its long term accumulator (LTA)is introduced in detail.The long term accumulator is the data reduction module of the correlator.Enhancing the integration of the circuit and the reliability of LTA, an improvement is presented by means of the study on the long term accumulator, to meet the new requirements for the correlator, such as higher speed and higher precision.Meanwhile, a specific way to implement the improvement and its traits after the improvement are introduced briefly.

A digital filter for bandwidth selection has obvious advantages on VLBI (Very Long Baseline Interferometry)data acquisition compared with the analog filter. This paper first reviews the development of digital filtering on VLBI data acquisition in Japan and NRAO (the National Radio Astronomy Observatory), then proposes two kinds of systematic implementation of digital filtering.The key factor to implement a filter is the speed of processing signals because of many high-speed arithmetic operations required.Reducing the computation time of digital filtering is important.The filter utilizes RAM look-up tables for tap weight multiplications.Three kinds of structures to realize the digital filter are compared here.Afterwards, the two kinds of systematic implementations are discussed in detail. With a steady advance in the technology of very high-density VLBI integrated circuits in recent years, FPGAs (Field Programmable Gate Array Integrated Circuits)are developed fast and have been proved to be powerful in many fields of digital signal processing.Finally, this paper gives a hardware layout to implement digital filtering based on FPGAs.

The Auto Guide Unit of the solar telescope is a feedback track system with high precision.Under the open loop control, it is difficult to reach tracking demand of the solar telescope;therefore, it is necessary to use the auto-guide unit as the feedback control system for the target position.In the process of tracking, there is an image rotation of the auto-guide unit, and if the effect of the image rotation is not considered, it can disable the auto-guide unit, therefore it s necessary to resolve the image rotation of the auto-guide unit.In this paper, the analysis of image rotation about the auto-guide unit of the solar telescope has been given theoretically, and the specific formula of the movement about the image in the CCD has been worked out.

A Faint Object Spectrograph and Camera (FOSC)for 1-meter telescope in Yunnan Observatory is introduced in this paper.It is a focal reduced camera type instrument and is mounted at the Cassegrain focus of 1-m telescope in Yunnan Observatory.The FOSC can be used in four different modes:direct imaging, long slit spectroscopy, slitless spectroscopy and coronography, and it is efficient and flexible.The optics design for the camera and for the spectrograph are shown.The light from the f/13.3 Cassegrain focus of the 1-m telescope is collimated by collimating lens then passes to the camera and images on the CCD detector.In the wavelegth range of 404.6nm -766.5nm, the image quality is 0.5"in diameter which encircles 80% of the energy in the 10'of the field.Four modes are as follows:1 　Direct Imaging:It is a focal reduced camera with a field of 10'.The focal ratio is f/7. The standard filters of B、V、R、I are mounted for selection. 2 Slitless Spectroscopy Mode:A direct vision prism is inserted into the parallel beam of the focal reduced camera to become a slitless spectroscopy.The dispersion of this slitless spectroscopy is 100nm/mm in 486.1 nm. 3 Long Slit Spectroscopy:The long slits are available to do spectroscopy with the direct vision prism.There are three slits mounted on a wheel in the Cassegrain focus.The slit size is 40mm×65μm (～1"), 40mm ×100μm (～1.5"), 40mm ×150μm (～2.25"), respectively. 4 Coronography Mode:A special plate is mounted on the slits wheel which is in the area of Cassegrain focus.The coronograph image can be obtained and the faint nebulosity around bright objects would be imaged with this mode.

Astrometric observations of major planets and their satellites are very important. These observations can be directly used for the improvement of the orbit theories of planets and their satellites, and also for the space exploration in our solar system.At present, some new techniques (such as radar ranging and interferometer)are available to observe the inner planets (Mercury, Venus and Mars)with high precision.Unfortunately, due to the principle limitations of these new techniques, the outer planets can be almost observed only using traditional optical methods, such as meridian circles.Since their "phase effects" on positional measurement, their positional accuracies, usually ±0."20～0."50 are poor.Recent observations adopt mainly an indirectly method, i.e.first observing a satellite of a planet and then deriving the planet'sposition by using the satellite'sephemeris.The accuracy of this method is usually in the range of ±0."10 ～ 0."20. It must be paid attention to the flaw of this method, i.e.with an assumption that the orbit theory of the satellite is precise enough.Obviously, the observed planet'sposition will be subject to the theoretical error of the satellite. Recently, Peng et al ^[1].have found a new method based on the edge-detection of Jupiter and obtained very good results with a standard deviation as small as ±0."03.A similar method has already applied to Saturn and its satellites ^[2].The results show that the geometric center of Saturnian ring has good precision better than ±0."05.In this paper, all used formulae of the image processing and related notions are given.We expect it, together with the papers ^[1,2] to be useful if some researchers are interested in this new method.

Yunnan province is located at the southwest part of China, and near the boundary of the Eurasian plate and the Indian plate.The extrusion of the Indian plate northeastward to the Eurasian plate causes complex geological features and high seismicity in the highland of Yunnan. The variety of seismic activity in Yunnan serves as a natural laboratory for seismological studies. The complexity in tectonics results in spatial non-uniformity of the earthquake distribution. Astronomical background of the rise and fall of strong seismic activities in the 20th century in Yunnan is analyzed in detail in this paper.The lunar nodal tides, generated by the variation of the inclination between the Moon'spath around the Earth and the equator with a period of 18.61 years may be a reason of the seismic activity with long periods.The analyzing result shows that three of the four strong seismic periods with earthquake magnitude larger than or equal to 6.7 in the 20th century started at the year or next year, when a maximum value of the inclination between the Moon's path around the Earth and the equator happened.Only the first seismic active period did not.Therefore, the total consistent probability is about 80%.Moreover, both the solar and seismic activities have a quasi-period of 11 years.On the basis of above we make an extension of the 4 groups with the period of 11 years by the earthquake with the most magnitude over years of the 20th century, and estimate the magnitude of the first earthquake in the future seismic active period in Yunnan.Considering the two astronomic factors, and according to the situation of the inclination between the Moon's path around the Earth and the equator, in addition to the solar activity at the present, we think that next seismic active period in Yunnan will probably start at AD 2006 or 2007, and it may last to 2015.During this period there will be more earthquakes with magnitude larger than or equal to 6.7.It means a new period with serious natural hazards in Yunnan.The location for the future first strong earthquake is also suggested in this paper.

In this article, first we recall the cultural circles in the ancient China, the method of the calamity forecasting was beginning from the combine of the numeric art and the astronomical culture.From that time to now the combine has been undergo three times.In the first time the rule of season completely determined by combining the temperature of atmosphere surface layer with the apparent motion of the Sun and the Moon, in the second time, the mystical astrology with the method of man-made calamities and celestial phenomena was generated, in the last time, the rule of climatic change by research on the combination of math-physical theorems and high upper-air general circulation was unveiled. At present, the three theorems of planetary atmospheric movement within the stratosphere and mesosphere are mentioned.Study on the incomplete ionospheric magnetic fluid from the main geomagnetic field, the cooling effect within adiabatic-compressed-restoring geomagnetic force lines, has been gained.The physical mechanics, the bool pool phenomena in high layer atmospheric circulation, are given. Finaly, from astronomical view, the atmosphere disaster prediction has been discussed