共查询到19条相似文献,搜索用时 515 毫秒
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对于一颗在大气外层不可分辨的恒星,当其光线通过地球大气层后,恒星的星像光度呈高斯分布;而子午仪光子计数观测记录下与其星像光度相关的轮廓曲线。采用模拟光子计数观测方法,求得恒星星像直径的经验公式。利用恒星的子午仪光子计数观测资料,使用最小二乘估计方法,并考虑到模拟计算星像直径的经验关系式,可以求出恒星子午仪光子计数观测的实测直径。用该方法对一组星的观测资料,求出其平均星像直径为3″.2。 相似文献
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云南天文台高分辨率斑点成像的新进展 总被引:2,自引:0,他引:2
本文报道了对天文目标:双星ADS16800、ADS16173,三星Hu66(ADS11344)和Hld171(ADS16648)进行的斑点成像观测及测量结果。介绍了所用的二维光子计数斑点像探测系统的性能,分析了探测系统的光子噪声、附加噪声和其它更复杂的噪声对斑点图的平均功率谱和重谱的影响。在讨论了改正重谱中的噪声偏差项时提出了对重谱基底施加正性约束的算法。测量的结果表明,实现了高精度的微射受限天文 相似文献
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谭征 《紫金山天文台台刊》1992,11(2):111-120
应当把探测效率作为光子探测系统的一个重要的总体性能指标,它标志了系统灵敏度发挥的程度。探测效率可以用相对统计比较法进行测算。过去的光子探测系统普遍存在漏计现象。因而探测效率明显偏低,作者对漏计的原因进行了探讨。提出克服漏计的方法。进而研制出一种新型高效光子计数检测系统,经过中星仪的试观测和等高仪的应用,证明该系统探测率高达95%以上,明显地提高了探测的极限和精度。 相似文献
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谭征 《紫金山天文台台刊》1995,14(2):146-158
本文对光子计数探测中堵塞漏计引起的非线性失真现象作了一些新的探讨相分析,提出了一套新的减少漏计的论证。该论证一旦实现,将会大大扩展光子计数探测的线性范围,进一步提高探测的灵敏度、信噪比和精度。 相似文献
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在光子计数资料的处理方法设计不完善时,有可能会大大影响光电等高仪的观测结果。本文提出了一套从平滑,搜索到定中心的光子计数资料处理方法,通过与原方法进行了9天(含满月夜)的同步处理比较,新的处理方法得到的星数是原方法结果的1.48倍,单星测定精度提高0″02,并且基本克服了天光的影响。 相似文献
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光子计数技术用于Ⅱ型光电等高仪观测系统 总被引:1,自引:0,他引:1
本叙述了Ⅱ型光电等高仪的一套完整的现代化观测系统,整个系统由IBM-286计算机进行实时控制、数据采集和结果处理,并且采用了光子计数的新技术,使光电等高仪的观测星等从原来的6^m.5提高到11^m.0。该系统已在上海天台、云南天台的Ⅱ型光电等高仪上正式使用,效果很好。 相似文献
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In astronomical photometry, the sensitivity of observations is limited by the dark counts of the photomultiplier tube. In the present work, the effect of dark count noise in photon counting systems is investigated by theory and experimental measurements. Dark counts are considered to be originating from two sources, namely: dc fluctuations and random pulses.Experimental measurements were carried out to determine noise effects in different operating regions of noise dominance. The results provide strong evidence that: in normal operating mode, where the effect of random pulses is dominant, dark counts do not follow Poisson statistics. The observed noise shows strong (1/f) power spectrum, where the observed noise power is found to increase with time of observation.The results are important in photon counting systems operating under dark count limited mode. The conclusions drawn can be useful in obtaining more accurate error estimates and in assessing astronomical photometric observations and data reduction techniques. 相似文献
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R. Poggiani 《Experimental Astronomy》2004,18(1-3):109-132
The domain of high speed optical astrophysics is still quite unexplored. The availability of 10 meter diameter telescopes
offers the unique possibility to investigate variability of faint objects at submillisecond time scales. In this paper I describe
the concepts of a photometer and a spectrometer for high speed astronomical observations. The instruments are based on a photon
counting detector developed for high energy physics, the Visible Light Photon Counter (VLPC). The detector has a quantum efficiency
in the visible as high as 88% and performs photon counting with sub microsecond time resolution. The photometer is built using
VLPC arrays. Adding a grating a VLPC array can be used in a time resolved spectrograph with medium resolution. This paper
develops, starting from experimental data, the concept of the two VLPC based instruments and their application to time resolved
photometry and spectroscopy of compact objects (pulsars, cataclysmic variables, low mass X-ray binary systems etc) and optical
counterparts of Gamma Ray Bursts. The high speed optical observations are the ideal complement to X/γ rays and gravitational
wave studies. The application of the instruments to the optical photometry of pulsars, the spectrophotometry of the prompt
optical flash from Gamma Ray Bursts and the study of binary systems are discussed in detail: in the last two applications
the instruments offer better opportunities than existing instruments. 相似文献
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恒星干涉仪的关键技术之一是用自适应光学技术来调节两相干光束之间的夹角,以保证干涉条纹可见度的损失最小。在我们的恒星干涉仪实验系统中,光束方向矫正系统就是为这一目的而研制的.该系统中的光子计数系统和8098单板机的软、硬件组成了补偿光束方向随大气扰动而变的系统.文章介绍了该伺服系统以及在实验系统联调时的试验结果。 相似文献
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在自适应光学系统中,波前探测器的噪声、未完全补偿湍流所引起的误差以及变形镜的拟合误差是主要的误差源.本文针对已经建立的2.16m望远镜红外自适应光学系统,从伺服控制系统的角度分析了该系统的闭环噪声、大气湍流引起的误差以及该系统的闭环总体误差.该系统的闭环总体误差是光强及系统闭环带宽的函数.本文还分析了该系统的有效性以及对大气湍流不同改善程度情况下光强与闭环带宽的关系.并在此基础上给出了该系统的最佳带宽选取及系统的极限工作星等. 相似文献
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N. Solomos 《Astronomische Nachrichten》2008,329(3):252-254
This contribution aims to introduce the idea that a well‐evolved HTN of the far future, with the anticipated addition of very large apertures, could also be made to incorporate the ability to carry out photonic astronomy observations, particularly Optical VLBI in a revived Hanbury‐Brown and Twiss Intensity Interferometry (HBTII) configuration. Such an HTN could exploit its inherent rapid reconfigurational ability to become a multi‐aperture distributed photon‐counting network able to study higher‐order spatiotemporal photon correlations and provide a unique tool for direct diagnostics of astrophysical emission processes. We very briefly review various considerations associated with the switching of the HTN to a special mode in which single‐photon detection events are continuously captured for a posteriori intercorrelation. In this context, photon arrival times should be determined to the highest time resolution possible and extremely demanding absolute time keeping and absolute time distribution schemes should be devised and implemented in the HTN nodes involved. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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Photon counting strategies with low-light-level CCDs 总被引:1,自引:0,他引:1
A. G. Basden C. A. Haniff C. D. Mackay 《Monthly notices of the Royal Astronomical Society》2003,345(3):985-991
Low light level charge-coupled devices (L3CCDs) have recently been developed, incorporating on-chip gain. They may be operated to give an effective readout noise of much less than one electron by implementing an on-chip gain process allowing the detection of individual photons. However, the gain mechanism is stochastic and so introduces significant extra noise into the system. In this paper we examine how best to process the output signal from an L3CCD so as to minimize the contribution of stochastic noise, while still maintaining photometric accuracy.
We achieve this by optimizing a transfer function that translates the digitized output signal levels from the L3CCD into a value approximating the photon input as closely as possible by applying thresholding techniques. We identify several thresholding strategies and quantify their impact on the photon counting accuracy and the effective signal-to-noise ratio.
We find that it is possible to eliminate the noise introduced by the gain process at the lowest light levels. Reduced improvements are achieved as the light level increases up to about 20 photon pixel−1 and above this there is negligible improvement. Operating L3CCDs at very high speeds will keep the photon flux low, giving the best improvements in signal-to-noise ratio. 相似文献
We achieve this by optimizing a transfer function that translates the digitized output signal levels from the L3CCD into a value approximating the photon input as closely as possible by applying thresholding techniques. We identify several thresholding strategies and quantify their impact on the photon counting accuracy and the effective signal-to-noise ratio.
We find that it is possible to eliminate the noise introduced by the gain process at the lowest light levels. Reduced improvements are achieved as the light level increases up to about 20 photon pixel
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David Clarke Gerry Deighan Gillian Fry Susan Goodsir Donald Macleod 《Astrophysics and Space Science》1996,239(2):229-235
Experiments are described which demonstrate that the dead-time constant associated with a photon counting stellar photometer/polarimeter is readily determinable by the application of the Malus law. It is also proposed that corrections for dead-time losses should be applied by an iteration technique to the exact equation rather than using the available approximation formulae. 相似文献
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为了探索对较暗目标进行成像的新方法,我们在TI公司生产的带有增益寄存器的EMCCD(Electron Multiply CCD)芯片基础上,构建了一套成像系统,主要用于对此芯片进行性能测试,为将来构建天文观测用相机做准备。本文主要介绍了EMCCD的结构特点、工作原理,并且详细介绍实验室采用TI公司的EMCCD搭建的成像系统,以及在此系统基础上对EMCCD进行地评测。 相似文献
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N. S. Nightingale 《Experimental Astronomy》1990,1(6):407-422
A new Silicon avalanche photodiode photon counting detector module with a peak detection efficiency of 45% and a maximum counting rate of more than 3,000,000cts/sec is described and its performance assessed over a range of operating conditions. The module should prove ideal for a wide variety of astronomical instrumentation as it covers the spectral range 350–1050nm and is compact, rugged and relatively cheap. 相似文献