MiCPhot： A prime-focus multicolor CCD photometer on the 85-cm Telescope

We describe a new BVRI multicolor CCD photometric system situated at the prime focus of the 85-cm telescope at the Xinglong Station of NAOC. Atmospheric extinction effects, photometric accuracy and color calibration dependence of the system are investigated. Additional attention was paid to giving observers guidance in estimating throughput, detection limit, signal-to-noise ratio and exposure time.     

Eclipses and Occultations of Galilean Satellites Observed at Yunnan Observatory in 2003

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.     

大天区望远镜中sCMOS相机的测光精度分析

与传统CCD (Charge Coupled Device)相机相比, s COMS (scientific Complementary Metal Oxide Semiconductor)相机被广泛装备于超大天区巡天设备,与传统CCD相机不同的是sCMOS相机采用卷帘式快门,因此对其进行测光精度的分析工作是很有意义的.首先,将s CMOS相机拍摄的图像与UCAC2 (The Second U.S. Naval Observatory CCD Astrograph Catalog)星表进行匹对,识别图像中的UCAC2标准星.接着对图中的标准星进行测光并提取测光数据进行最小二乘直线拟合,获得了相应的系统转换系数并得到仪器星等至标准星等的转换公式.然后,将转化后的仪器星等和标准星等做差并计算相应的均方根误差.最后,利用计算得到的均方根误差评估sCMOS相机的测光精度,并将标准星按星等划分后,分析了相应的测光误差.计算结果表明在标准测光夜测量亮度亮于14等的星时,测光精度优于0.15 mag.通过实测精度分析可知卷帘快门sCOMS相机具有较高的测光精度,基本满足空间碎片巡天观测的要求.     

Discovery of Four Peculiar Variable Stars

Four stars, GSC 1258-0143, GSC 1986-1665, GSC 3045-0892 and GSC 2983-1597 were found to be new variables during a campaign of CCD photometric monitoring of short-period eclipsing binary stars. The variabilities of these new variables are reported. The main characteristics and probable classifications of the variables are discussed through a preliminary analysis on their light curves. Among these stars, GSC 1258-0143 is classified as a RR Lyr star of sub-type a. Its pulsation period is determined to be about 0.5206 days. The other three stars, are definite variables, but their periods and types of light variations remain unknown.     

The irregular variable KU Her: The light and period variations

We present CCD photometric observations of the slow irregular type variable KU Her. We have also used observations from the ASAS Database and the AAVSO International Database. The V-band observations span eight years from August of 2002 to September of 2010. The length and density of the data enable us to look for variations on time scales ranging from days to years. The V-band observations of KU Her are analysed to derive periodicity. This analysis was an approach to find the fundamental periods of the variability of KU Her. Analysis of the KU Her light variation indicates a complex combination of different periods. Five main and three harmonic periods are identified. In addition to the period analysis, we present the colour variations of the star.     

兴隆60 cm望远镜主焦CCD系统测光性能的研究

对兴隆６０ｃｍ望远镜主焦ＣＣＤ系统的测光性能进行了测试和研究．测定了ＣＣＤ快门时间函数,讨论了快门延迟效应对短时间曝光观测的可能影响．通过观测大批Ｌａｎｄｏｌｔ标准星,较准确地定出了ＢＶＲＩ宽带测光的星等系统转换关系,结果表明本系统与标准ＢＶＲＩ系统很接近．对ＣＣＤ系统的天文测光精度作了仔细的检验和分析,并对ＰＳＦ拟合测光和孔径测光两种方法进行了比较     

Searching for Variable Stars in the Field of NGC 7789

We present the results of a time-series CCD photometric survey of variable stars in the field of the open cluster NGC 7789. In a field of about one degree centering on the cluster, a total of 28 new variable stars are discovered (14 W UMa systems, nine EA-type eclipsing binaries, one RR Lyr star, and four unclassified). In addition, we recovered 11 old variables previously discovered by other authors. Preliminary parameters are given for some of these variables.     

Short Time-Scale Variability in the Light Curve of~TW~Draconis

We have re-analyzed old photometric UBV data obtained by Papoušek et al. at Skalnaté Pleso, Slovakia (1967–1980) and Brno, Czech Republic (1976–1979) observatories and analyzed new own CCD measurements (Brno, 2003–2005). In both set of photometric data the oscillations in the vicinity of the primary minimum were found. The detected periods are compatible with the previously published ones.     

施密特望远镜CCD BVRI测光系统的初步研究

本文利用Thomson CCD,在北京天文台兴隆站施密特望远镜上进行BVRI四色测光,得到了该测光系统的颜色转换方程,并对所得结果进行了分析探讨。同时论证了BAO-CCD系统在施密特望远镜上用于测光的可行性。     

Faint UBVRI CCD sequences for wide-field surveys – II. UBVR sequences at δ=−30°

We present results from a continuing campaign to secure deep multi-colour CCD sequences for photometric calibration in UK Schmidt fields with galactic latitudes | b |>50°. In this paper we present UBVR photometry in 12 fields and BR photometry in a further 14 fields observed within UK Schmidt survey fields centred at δ =−30°. Photometric errors are at the 0.05 level at 20.2, 21, 20.5 and 20 mag for UBVR sequences respectively. Our observations were carried out with the 0.9-m telescope at the Cerro-Tololo Inter-American Observatory. These data are not intended for use as highly accurate individual photometric standards, but rather for use as sequences, using a large number of stars to calibrate wide-area data such as photographic plates. The data are available electronically at http://icstar5.ph.ic.ac.uk/~scroom/phot/photom.html .     

The multi-band CCD photometric investigation of short-period eclipsing binary V1044 Her

We present new CCD photometric observations of V1044 Her obtained on May 22, 23 and 24, 2015. From our data, we derived five new light curve minimum times. Combining our new results with previously available CCD light minimum times, we derived an updated ephemeris and discovered that the period of this binary system exhibits an oscillation. The cyclic variation may be caused by the light-time effect via the presence of a third body or magnetic activity cycle. We calculated the corresponding period of the third body to be 14.1 ± 1.4 years or magnetic cycle to be 12.2 ± 0.7 years. We analyzed our new asymmetric light curves to obtain photometric solutions and starspot parameters using the Wilson and Devinney program. The final results show that V1044 Her is a contact binary system with a degree of contact factor f = 3.220( ± 0.002)%.     

Color-Redshift Relations and Photometric Redshift Estimations of Quasars in Large Sky Surveys

With a recently constructed composite quasar spectrum and the X2 minimization technique, we describe a general method for estimating the photometric redshifts of a large sample of quasars by deriving theoretical color-redshift relations and comparing the theoretical colors with the observed ones. We estimated the photometric redshifts from the 5-band SDSS photometric data of 18678 quasars in the first major data release of SDSS and compared them with their spectroscopic redshifts. The difference is less than 0.1 for 47% of the quasars and less than 0.2 for 68%. Based on the calculation of the theoretical color-color diagrams of stars, galaxies and quasars both on the SDSS system and on the BATC system, we expect that we would be able to select candidates of high redshift quasars more efficaciously with the latter than with the former, provided the BATC survey can detect objects with magnitudes fainter than 21.     

二维CCD图象数据压缩

本文着重指出了在今后处理大面积CCD图象数据过程中,所将面临的数据存贮困难问题.本文提出了一种有效的不丢失天文信息的压缩CCD图象数据的方法,对银纬b=-60°的一个天区的试验表明,压缩后的图象数据仅为原图象数据的1/30左右,并且可以十分方便地进行图象再现及再处理。在压缩数据过程中,我们在剑桥APM底片扫描机参数化施密特照相底片的基础上,重新安排了CCD图象上天体的对应参数,并视天体的大小及形状,有效地提取保存了天体周围矩阵信息.     

VRI photometry of M67 for CCD standardization at 2.3m VBT

We present the results from CCD photometry in theV, R andI bands, of the ‘Dipper Asterism’ region of the open cluster M67 based on observations carried out at the prime focus of the 2.3 m Vainu Bappu Telescope of the Vainu Bappu Observatory, Kavalur. The CCD parameters like the system gain and the readout noise are measured using several flatfield frames taken through the standardI filter. The CCD chip is calibrated using the photometric standards in the field and linear colour transformation relations are derived. Also a few newVRI photometric measurements are reported for the members of the cluster.     

Determination of the Photometric Calibration and Large-Scale Flatfield of the STEREO Heliospheric Imagers: I. HI-1

The aim of this paper is to calculate an accurate large-scale flatfield for the STEREO HI-1 instruments. This is done by analysing the variation in intensity of stars in the background starfield as they pass across the CCD. In order to use the background starfield, a photometric calibration is performed which defines a HI magnitude scale and a conversion between this scale and measured intensity. The photometric calibration uses stellar spectra folded through the instrument response to make initial intensity predictions. However, a secondary prediction method based on the photometric calibration, which blends the R-, V- and B-magnitudes of a star, is derived for stars with no spectral information.     

Photometric study of the FUor star V 1735 Cyg (Elias 1-12)

Results from optical photometric observations of the PMS star V 1735 Cyg are reported. The star is located in the IC 5146 dark cloud complex—a region of active star formation. On the basis of observed outburst and spectral properties, V 1735 Cyg was classified as a FUor object. We present data from BVRI CCD photometric observations of the star, collected from March 2003 to January 2009. Plates from the Rozhen Schmidt telescope archive were scanned for a brightness estimation of the star. A sequence of sixteen comparison stars in the field of V 1735 Cyg was calibrated in BVRI bands. The data from photographic observations made from 1986 to 1992 show a strong light variability (ΔV=1_⋅^m2). In contrast, the recent photometric data obtained from 2003 to 2009 show only small amplitude variations (ΔI=0_⋅^m3). The analysis of existing photometric data shows a very slow decrease in star brightness—1_⋅^m8 (R) for a 44 year period. The possibilities for future photometric investigations of V 1735 Cyg using the photographical plate archives is discussed briefly.     

鹿林彗星的断尾事件研究

鹿林彗星在2009年2月4日(UT)发生了一次断尾事件,通过对2月4日前后的观测数据进行分析,发现在2月3日鹿林彗星就已发生过一次断尾事件.对2月3日发生的断尾事件进行研究可得出断尾移动的速度为68 km·s-1,断尾事件发生的时间为2009年2月3日(15.24土5.16)时.结合断尾事件发生前后鹿林彗星的轨道特征和STEREO-A飞船所测量到的太阳风数据,鹿林彗星2月3日发生的断尾事件可能是由于日冕物质抛射和彗星相互作用导致的磁重联引起的.     

Apex I and Apex II software packages for the reduction of astronomical CCD observations

We describe in detail the Apex I and Apex II software packages created for astrometric and photometric reductions of astronomical observations with CCD cameras. The Apex I software package has been created for the semiautomatic reduction of astronomical observations and has a convenient user interface. The Apex II software package allows for the completely automatic reduction of astrometric and photometric observations to be performed.     

New photometric investigation of the Herbig Ae/Be star HD 52721, a close binary system: Evidence for the existence of large-scale azimuthal inhomogeneities

We present new results of our photometry for the Herbig Be star HD 52721 obtained from January 16 to March 25, 2013. A new data reduction technique is used. Using this technique, we have also reanalyzed the previous results of our photometry for this object pertaining to the period from March 7 to March 28, 2010. The Be star HD 52721 is known as an eclipsing variable with the period P = 1^d. 610. Two photometric minima observed during one period are a peculiarity of its photometric variability. They are separated in phase of the period P by 0.5 and differ from one another in depth by 0 ^m . 04. We have also detected additional minima observed at the phases of maximum brightness. We hypothesize that they can be associated with the existence of local azimuthal inhomogeneities rotating synchronously with the orbital motion of the binary component stars in the circumstellar envelope. When processing our CCD frames, we have applied an efficient CCD-frame rejection method that has allowed the accuracy of observations to be increased considerably. The CCD frames have been further processed using the Apex II software package, which is a universal software platform for astronomical image processing. We justify the need for additional photometric observations of HD 52721 in various color bands to confirm the hypothesis about the existence of azimuthal inhomogeneities in the program binary system and to analyze their physical properties.     

Results of Optical Monitoring of Cataclysmic Variable GK Per in 2004

The preliminary results of ground-based UBV photometric and CCD observations of cataclysmic variable GK Per during the outburst in autumn of 2004 are presented.