共查询到20条相似文献，搜索用时 125 毫秒
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在１９９２年３月３１日至４月２日期间，我们利用云南天文台１ｍ望远镜２号ＣＣＤ和缩焦装置，对环星系ＮＧＣ４７３６进行了Ⅴ和Ⅰ波段深曝光观测。在经过Ｒｉｃｈａｒｄｓｏｎ－Ｌｕｃｙ图象复原以及自适应滤波两种方法处理后，发现仅仅在Ⅴ波段图象上，其核区存在一个直径约为１０″的环状结构。 相似文献
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在１９９２年３月３１日至４月２日期间，我们利用云南天台１ｍ望远镜２号ＣＣＤ和缩焦装置，对环星系ＮＧＣ４７３６进行了Ｖ和Ｉ波段深曝光观测。在经过Ｒｉｃｈａｒｄｓｏｎ－Ｌｕｃｙ图象复原以及自适应滤波两种方法处理后，发现仅仅在Ｖ波段图像上，其核区存在一个直径约为１０″的环状结构。 相似文献
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232MHz太阳爆发与日冕物质抛射 总被引：1，自引：0，他引：1
利用综合孔径射电望远镜的２３２ＭＨｚ观测太阳,具有３．８’的空间分辨率,２０ｍｓ的时间分辨率和高灵敏度及很好的抗干扰能力。１９９９年共观测到１２次大爆发,其中８次与日冕物质抛射相关,可以利用米波射电爆发预报ＣＭＥ事件。 相似文献
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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 相似文献
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用上海天文台１．５６ｍ望远镜和ＣＣＤ照相机，观测ｓ＝５碎片时，发现了类似彗尾的奇异现象。 相似文献
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大气湍流会导致天文图像的像质衰减，而视宁度r0则是描述这种衰减的特征参数。在本文中，我们给出了像运动法测量中r0和曝光时间之间的关系：曝光时间必须小于大气相干时间，否则测量的r0值将偏大。基于这个原因以及对仪器检测的需要，我们必须对视宁度测量仪的曝光时间进行准确地测量。为此我们设计了一种实验方法来测定视频CCD的曝光时间，实验的结果表明这种方法是可靠的。 相似文献
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对地方电视台转播CCTV时延的测定 总被引：1，自引：0，他引：1
讲述了同步广播卫星电视时间信号的测量方法和测量结果，获得了ＣＣＴＶ、ＣＣＴＶ２通过同一颗卫星（亚太－１Ａ）转播的时延差值为１６３．３３μｓ，测量精度在１０ｎｓ以内；ＣＣＴＶ２、ＣＣＴＶ４分别经两颗卫星（亚太－１Ａ，亚洲－Ⅱ）转播，在陕西天文台卫星地面接收站时延差值为１６４４．２０μｓ，严谨为５０μｓ，并分析了影响时延差值和精度的原因，同时测量了地方电视台转播亚太－１Ａ的ＣＣＴＶ信号与直接接收亚太－ 相似文献
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云南天文台丽江高美古和昆明的大气视宁度研究 总被引：5，自引：1，他引：4
研究云南天文台昆明凤凰山和丽江高美古两地点的大气视宁度。利用云南天文台于1994年建立的3孔较差视宁度监视仪（3孔DIMM），对这两个地点的视宁度对比观测。还利用云南天文台的1米望远镜所得到的视宁度与3孔DIMM所测的视宁度进行对比。1米望远镜和3孔DIMM同时观测了7个晚上，各取得308组数据，它们的视宁度平均分别为0．90〃和0．84〃。还讨论了3孔DIMM采用不同曝光时间对视宁度测量值的影响，从实验得出3孔DIMM采用20ms曝光比采用8ms曝光所测视宁度的值要好15％左右。从1995年5月－1996年12月，对丽江高美古和昆明凤凰山二地进行了视宁度的对比观测。在高美古和昆明分别观测了234夜和256夜，观测结果是两个点的视宁度平均；丽江为0．70〃，昆明为0．95〃，同时也统计了两个点的月平均视宁度和最好夜的视宁度，并讨论了两地视宁度随时间的变化规律。 相似文献
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A. Ziad R. Gredel J. Aceituno J. Borgnino F. Hoyo A. Irbah F. Martin U. Thiele S. Pedraz 《Monthly notices of the Royal Astronomical Society》2005,362(2):455-459
The main atmospheric optical parameters have been measured at the Calar Alto Observatory simultaneously using the Generalized Seeing Monitor (GSM) and a Differential Image Motion Monitor (DIMM) during several nights in 2002 May. The temporal evolution of the seeing, the outer scale, the isoplanatic angle and the coherence time have been analysed. There is excellent agreement between the seeing measurements provided by the two instruments, particularly when the turbulence is slow. Indeed, the GSM measurements are corrected from the exposure time when the DIMM data were recorded for at least 5 ms. From almost three years of DIMM (at 5 m height above ground) data, a seeing of 0.92 arcsec with a standard deviation of 0.31 arcsec has been obtained for this site. The outer scale , the isoplanatic angle θ0 and the coherence time τ0 measured with the GSM are well fitted with log-normal distributions with median values of 22.9 m, 2.27 arcsec and 3.7 ms, respectively. 相似文献
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Andrew Smith Jeremy Bailey J. H. Hough Steven Lee 《Monthly notices of the Royal Astronomical Society》2009,398(4):2069-2073
We present an empirical analysis of the effectiveness of frame selection (also known as lucky imaging) techniques for high-resolution imaging. A high-speed image recording system has been used to observe a number of bright stars. The observations were made over a wide range of values of D / r 0 and exposure time. The improvement in Strehl ratio of the stellar images due to aligning frames and selecting the best frames was evaluated as a function of these parameters. We find that improvement in Strehl ratio by factors of 4–6 can be achieved over a range of D / r 0 from 3 to 12, with a slight peak at D / r 0 ∼ 7 . The best Strehl improvement is achieved with exposure times of 10 ms or less, but significant improvement is still obtained at exposure times as long as 640 ms. Our results are consistent with previous investigations but cover a much wider range of parameter space. We show that Strehl ratios of >0.7 can be achieved in appropriate conditions whereas previous studies have generally shown maximum Strehl ratios of ∼0.3. The results are in reasonable agreement with the simulations of Baldwin, Warner & Mackay. 相似文献
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Kaufmann P. Trottet G. Giménez de Castro C.G. Costa J.E.R. Raulin J.-P. Schwartz R.A. Magun A. 《Solar physics》2000,197(2):361-374
We present an analysis of the time profiles detected during a solar impulsive flare, observed at one-millimeter radio frequency (48 GHz) and in three hard X-ray energy bands (25–62, 62–111, and 111–325 keV) with high sensitivity and time resolution. The time profiles of all emissions exhibit fast time structures of 200–300 ms half power duration which appear in excess of a slower component varying on a typical time scale of 10 s. The amplitudes of both the slow and fast variations observed at 48 GHz are not proportional to those measured in the three hard X-ray energy bands. However, the fast time structures detected in both domains are well correlated and occur simultaneously within 64 ms, the time resolution of the hard X-ray data. In the context of a time-of-flight flare model, our results put strong constraints on the acceleration time scales of electrons to MeV energies. 相似文献
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Abstract— The cosmogenic radionuclides, 10Be, 26Al, 36Cl, and 53Mn were measured in selected clasts and matrix samples from the howardite Kapoeta. Previous measurements of cosmogenic 21Ne indicate higher cosmic‐ray exposure ages for bulk samples than for some separated clasts or mineral separates. A possible interpretation for this difference in apparent exposure ages is a complex recent exposure history for Kapoeta. In this scenario some constituents are exposed to cosmic rays in a 2π geometry as part of a larger body immediately preceding its 4π exposure in a smaller body. To test this scenario we measured cosmogenic radionuclides in several clasts from Kapoeta. These measurements are consistent with a simple single‐stage 4π exposure history during which the entire inventory of cosmogenic radionuclides was produced. Taken together, these data are most consistent with a single‐stage 4π exposure lasting ～3 Ma. This scenario is nevertheless consistent with models in which the exposure of some constituents of Kapoeta to energetic particles occurred at an earlier time, as is indicated by 21Ne measurements. However, from our data we conclude that insubstantial quantities of cosmogenic radionuclides were inherited from this earlier irradiation; this earlier exposure to energetic particles must have predated the recent exposure by at least ～10 Ma to allow for the decay of the long half‐life cosmogenic radionuclides. 相似文献
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Ksanfomaliti L. V. Dzhapiashvili V. P. Kakhiani V. O. Kvaratskheliya O. I. Korol' A. N. Mayer A. K. Petashvili P. P. 《Solar System Research》2001,35(3):190-194
December 1–3, 1999, observations of the planet Mercury were carried out at the Abastumani Astrophysical Observatory of the Republic of Georgia by the short exposure method with the aid of a charge-coupled device (CCD) camera. The materials of these observations are presented in this paper. It is shown that the reduction of the exposure down to 10 ms eliminates the image blurring caused by the atmospheric instability and considerably improves resolution. As regards the image distortions, they can be eliminated only by selecting acceptable images from a sufficiently large number of pictures obtained. The short exposure method allows one to obtain new results from the ground-based observations of Mercury. 相似文献
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P. Kaufmann F. M. Strauss J. E. R. Costa B. R. Dennis A. Kiplinger K. J. Frost L. E. Orwig 《Solar physics》1983,84(1-2):311-319
Simultaneous microwave and X-ray observations are presented for a solar flare detected on May 8, 1980 starting at 19:37 UT. The X-ray observations were made with the Hard X-Ray Burst Spectrometer on the Solar Maximum Mission and covered the energy range from 28–490 keV with a time resolution of 10 ms. The microwave observations were made with the 5 and 45 foot antennas at the Itapetinga Radio Observatory at frequencies of 7 and 22 GHz, with time resolutions of 100 ms and 1 ms, respectively. Detailed correlation analysis of the different time profiles of the event show that the major impulsive peaks in the X-ray flux preceded the corresponding microwave peaks at 22 GHz by about 240 ms. For this particular burst the 22 GHz peaks preceded the 7 GHz by about 1.5 s. Observed delays of the microwave peaks are too large for a simple electron beam model but they can be reconciled with the speeds of shock waves in a thermal model. 相似文献
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The circular polarization of complex solar bursts was measured at short microwaves (22 GHz, × 1.35 cm) with high sensitivity (0.03 s.f.u. r.m.s.) and high time resolution (5 ms). The polarization shows up as soon as an excess burst emission is measured. Two components are found in the time development of the degree of circular polarization: (1) a steady level, sometime changing smoothly with time; (2) superimposed faster polarization time structures, small compared to the basic steady degree of polarization, and often not clearly related to the burst flux time structures. The observed degrees may range from 10% to more than 85%.In memoriam (1942–1981). 相似文献
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A solar flare occurring on 26 February, 1981 at 19:32 UT was observed simultaneously in hard X-rays and microwaves with a time resolution of a fraction of a second. The X-ray observations were made with the Hard X-ray Monitor on Hinotori, and the microwave observations were made at 22 GHz with the 13.7 m Itapetinga mm-wave antenna. Timing accuracy was restricted to 62.5 ms, the best time resolution obtained in hard X-rays for this burst. We find that: (a) all 22 GHz flux structures were delayed by 0.2–0.9 s relative to similar structures in hard X-rays throughout the burst duration; (b) different burst structures showed different delays, suggesting that they are independent of each other; (c) the time structures of the degree of polarization at 22 GHz precede the total microwave flux time structures by 0.1–0.5 s; (d) The time evolutions of time delays of microwaves with respect to hard X-rays and also the degree of microwave polarization show fluctuations with are not clearly related to any other time structures. If we take mean values for the 32 s burst duration, we find that hard X-ray emission precedes the degree of microwave polarization by 450 ms, which in turn precedes the total microwave flux by 110 ms. 相似文献