Q. Y. Peng

Jinan University (Guangzhou, China) · Department of Computer Science

In the Caviar software package, a standard tool for astrometry of images from the Cassini Imaging Science Subsystem (ISS), Gaussian fitting is used to measure the centre of point-like objects, achieving a typical precision of about 0.2 pixels. In this work, we consider how alternative methods may improve on this. We compare three traditional centro...

755 new CCD observations during the years 2014-2016 have been reduced to derive the precise positions of Triton, the first satellite of Neptune. The observations were made by the 1 m telescope at Yunnan Observatory over fifteen nights. The positions of Triton are measured with respect to the stars in Gaia DR1 star catalogue. The theoretical positio...

Very recently, Heinze & Metchev proposed a novel method for calculating precise distances to the main-belt asteroids using only two nights of data from a single observatory. In this paper, we re-derive the solution but use easily understood spherical astronomy. Our derivation is based on the premise that the geocentric angular velocity of an astero...

In order to study the potential in high precision CCD astrometry of irregular satellites, we have made experimental observations for Himalia, the sixth and irregular satellite of Jupiter. A total of 185 CCD observations were obtained by using the 2.4 m telescope and 1 m telescope at Yunnan Observatories over ten nights. Preliminary analysis for the...

298 CCD observations during the year 2013 have been reduced to derive the precise positions of near-Earth asteroid (99942) Apophis. The observations were made by the 2.4-m telescope at Yunnan Observatory over 10 nights. The position and proper motion errors of the reference stars in the USNO CCD Astrograph Catalogue 4 (UCAC4) star catalogue are cor...

Aims: Astrometric observations performed by the Gaia Follow-Up Network for Solar System Objects (Gaia-FUN-SSO) play a key role in ensuring that moving objects first detected by ESA's Gaia mission remain recoverable after their discovery. An observation campaign on the potentially hazardous asteroid (99 942) Apophis was conducted during the asteroid...

Single-frame super resolution (SR) image reconstruction algorithms based on maximum a posteriori (MAP) have preferable reconstruction results and noise robustness but high time and space complexity. To improve efficiency of template convolution-based MAP (TC-MAP) algorithm and decrease its memory consumption, a new image-content-based adaptive bloc...

346 new CCD observations during the years 2011–2014 have been reduced to derive the precise positions of Phoebe, the ninth satellite of Saturn. The observations were made by the 2.4 m telescope at Yunnan Observatory over nine nights. Due to the use of a focal-reducer on the telescope, its significant geometric distortion is solved for and removed f...

Characters are concerned in many image processing applications. Enhance resolutions of character images frequently lead to higher recognition rate. Considering vertical, horizontal and diagonal texture features of character images, a new image smoothness measurement as well as a new method for extracting image texture in different directions is pro...

Context. In 2009, the Sun and the Earth passed through the equatorial plane of Jupiter and therefore the orbital planes of its main satellites. It was the equinox on Jupiter. This occurrence made mutual occultations and eclipses between the satellites possible. Experience has shown that the observations of such events provide accurate astrometric d...

In this paper, the error analysis has been done for the linear approximate transformation between two tangent planes in celestial sphere in a simple case. The results demonstrate that the error from the linear transformation does not meet the requirement of high-precision astrometry under some conditions, so the linear approximate transformation sh...

The ephemeris of Phoebe, the ninth satellite of Saturn, is not very accurate. Previous dynamical models were usually too simplified, the astrometry is heterogeneous and, the Saturn's ephemeris itself is an additionnal source of error. The aim is to improve Phoebe's ephemeris by using a large set of observations, correcting some systematic errors an...

The table provides the statistics of astrometric residuals of Phoebe's ephemeris PH12. Number of accepted observations, total number of observations, mean and root mean square (rms) of the residuals in right ascension (R.A.) and declination (Dec.) and time-span are indicated for each bibliographic reference. Symbol * indicates that the observations...

A simple but effective approach is proposed for measuring the geometric distortion of a CCD field of view of a ground-based telescope. For three open clusters (M35, M67, and NGC 2324), 425 CCD frames taken by a 1 m telescope at the Yunnan Observatory are used to test this approach. It is found that the geometric distortion pattern depends strongly...

Geometric Distortion (GD) is an important factor in high-precision positional measurement. In this paper, some experiments have been conducted in order to analyze the GD's effect on the positional measurement of Phoebe, the ninth satellite of Saturn. The approach we recently proposed in the paper [1] has been used to process our observed data in or...

We observed the open clusters NGC 1664 (43 exposures) and M35 (42 exposures) by the Yunnan Faint Object Spectrograph and Camera in the 2.4 m telescope at Yunnan Astronomical Observatory on 2011 January 3, and processed them by a method recently proposed by us. The result shows that there is a geometric distortion effect in the field of view and the...

Effective point-spread function (ePSF) method is an excellent method for the stars' positional measurements in stellar images, whose critical step is constructing an accurate ePSF mode. In the study, we investigated the effect of the grid density on the mode's accuracy by some experiments on processing synthetic stellar images in which all stars ha...

The Working Group on the Natural Planetary Satellites has been created to promote the development of high-quality ephemerides. The Working Group encourages theoretical studies, coordinated observations, and makes all data available to the users through the NSDC web site (http://www.imcce.fr/nsdc).

In this paper, we present 526 precise CCD positions of Galilean satellite-pairs of Jupiter, which have been extracted from 441 CCD frames captured by a 1-m telescope at the Yunnan Observatory from 2002 to 2010. The four Galilean satellites (Io, Europa, Ganymede and Callisto) are used to calibrate the CCD field of view by comparing their pixel posit...

In this paper we propose a novel method based on the characteristics of the object that we are interested in to distinguish it from other stars, whose images are line-shaped trails. The point-like object and streak-like stellar images become more visible after some pre-processing, and operated by boundary tracking, then they can be preliminarily id...

The images of the open cluster NGC2168 are taken using the newly-fitted 2k×2k CCD attached to the 1-m telescope at the Yunnan Observatory with two different orientations. After the catalogue position of a star from UCAC2 is compared with its corresponding measured position, a surprising result shows that a small field of view (about 7’×7’) exhibits...

One of important objectives of astronomical observations is to obtain physical information, including positions of measured stars with high accuracy from digitized CCD images. By means of CCD images taken by the 1m telescope at Yunnan Observatory, research on the comparison of the accuracy among three often-used centering algorithms is carried out,...

Context. In 2003, the Sun and the Earth passed through both the equatorial plane of Jupiter and therefore the orbital planes of its main satellites. Aims. During this period, mutual eclipses and occultations were observed and we present the data collected.Methods. Light curves of mutual eclipses and occultations were recorded by the observers of th...

This paper presents 2154 precise positions of Saturn and its major satellites from 359 CCD exposures taken with the 1 m telescope at the Yunnan Observatory during the years 2002–2006. It also describes the improved image-processing techniques for the pixel positional measurement of Saturn's rings and its major satellites, especially for Mimas and E...

After a CCD image of the four Galilean satellites of Jupiter is obtained by a long focal length telescope, we can compare the theoretical positions of these satellites with their pixel positions so as to obtain the calibration parameters of the CCD field of view. In theory, when two of the four satellites have small enough separation, their relativ...

The optical ground-based astrometry of solar system objects may have its accuracy strongly improved by using new methods for making observations and reductions of them. New photometric methods of observating the mutual phenomena occurring in the solar system, may provide astrometric data with a higher precision than the classical direct imaging. In...

In order to determine precisely positions of the Galilean satellites of Jupiter, it is useful that shortly before and/or after photometric observations of a mutual event, normal CCD imaging observation is also performed for the two small-separation satellites. Experimental observations showed that the two observational types, on the whole, could de...

We describe and analyze observations of mutual events of Galilean satellites made at the Yunnan Observatory in February 2003 from CCD imaging for the first time in China. Astrometric positions were deduced from these photometric observations by modelling the relative motion and the photometry of the involved satellites during each event.

This paper presents 210 positions of Phoebe, the ninth satellite of Saturn, observed with the 1-m telescope at the Yunnan Observatory during the years 2003–2005, using a CCD image-overlapping calibration method proposed recently by Peng et al. After the observed positions of Phoebe are compared with its theoretical positions computed by the new JPL...

The image-processing techniques used by Peng et al. are further improved to measure precisely the positions of Saturn and its satellites. 495 CCD images taken with the 1-m telescope at the Yunnan Observatory during the years 2002–2004 are processed with these techniques. These measured pixel positions are compared to their theoretical positions com...

A precise astrometric calibration method is presented for a CCD image with a small field of view. Its detailed computational formulae are given, and its feasibility and accuracy are tested by the observations of both the star and Phoebe, the 9th satellite of Saturn. This new method can also be applicable to other planetary satellites, asteroids and...

After overcoming the deficiencies of previous image-processing techniques, a novel technique based on the edge-detection of Saturnian ring is developed to precisely measure Saturn’s position. Furthermore, the scattering light (i.e. halo light) of Saturn and its ring is removed effectively based on its center symmetry. Therefore, we have much more o...

Two image-processing techniques are developed to measure precisely the positions of Jupiter and its Galilean satellites. One is used to detect the edge of Jupiter's CCD image and fit it with an ellipse, thereby obtaining the planetary center. The other is used to remove the positional effect of Jupiter's scattering light that has on the measurement...

A positional measuring procedure for the eight major satellites of Saturn (Mimas, Enceladus, Tethys, Dione, Rhea, Titan, Hyperion and Iapetus) is developed. Using this procedure, 199 frames of CCD images, obtained with the 1-meter telescope at the Yunnan Observatory from 1996-2000, are measured. These positions are compared to the ones computed wit...

CCD images for two Galilean satellites: Europa, Callisto and a bright star in Hipparcos Catalogue (No.104297) are obtained on 1 meter telescope at the Yunnan Observatory on the night of Nov.14, 1997. After the two satellites were measured for the scale and orientation of CCD frames, the apparent positions for the star were determined with respect t...

199 frames of CCD images of the major satellites of Saturn (Mimas, Enceladus, Tethys, Dione, Rhea, Titan, Hyperion and Iapetus), obtained on 1-meter telescope at the Yunnan Observatory during the years of 1996-2000, are measured. These positions are compared to the ones computed with the Vienne & Duriez ephemerides (TASS1.7). The calibrated paramet...