上海天文台1．56米望远镜斑点干涉成像实验进展

斑点干涉成像技术是克服大气湍流影响,提高地面大口径望远镜分辨本领的有效途径之一。该技术利用斑点相机拍摄一系列的短曝光像,使得大气湍流冻结,再经过图像处理获得高分辨率重建像。该技术设备简单,易于实现,很快在观测天文学中得到了广泛的应用,尤其是对双星的研究。首先回顾了天文高分辨率重建技术的发展,并介绍了相关研究成果。描述了几种典型的斑点干涉成像处理方法及其优缺点。对图像噪声类型及滤波方法进行了分析。在上海天文台1．56m望远镜上开展了双星斑点干涉观测实验,目标星等4～7mag,双星目标星等差小于2。分别采用斑点干涉术和迭代位移叠加法成功实现了双星目标的高分辨率成像,初步证明了在1．56m望远镜上进行斑点干涉成像实验,能够达到接近望远镜衍射极限的分辨率水平。     

斑点图的重心与波前倾斜

论述了斑点图重心与瞬时波前倾斜的关系,证明了斑点图重心位置与瞬时波前倾斜的一致性,这种一致性无论光瞳孔径是否大于大气相干长度均是成立的.这一结论并未严格受限于近场近似条件,结论的一个重要推论是:用重心对准的位移叠加法对斑点图进行统计后所得到的传递函数就是大气望远镜综合系统的平均短曝光传递函数,该推论对于自适应光学和高分辨率图像重建技术均具有非常重要的意义.     

云南天文台新型斑点象探测系统

斑点成象技术能有效地消除地球大气湍流的不良影响,实现地基大型天文望远镜的衍射受限分辨率成象,其所需的原始数据是天文目标及参考星的一系列的短曝光斑点象,它们取自望远镜的终端设备：斑点象探测系统。文中对比该技术对原始数据的要求：介绍了云南天文台研制的新型斑点象探测系统的结构和性能。实际观测结果表明,该系统基本能满足要求。     

应用自适应光学望远镜所取得的天文观测成果

自适应光学技术已经成为现代地基天文光学望远镜的重要部分。在世界各地的天文台中 ,许多大型光学望远镜的自适应光学系统正在建造 ,不少的系统已经投入使用。自适应光学技术经过二十多年的发展 ,取得了越来越多的令人激动的天文观测成果 ,自适应光学正在接近成熟并正向天文实际应用的阶段转化。本文根据近几年来自适应光学望远镜在天文中的应用 ,对其所取得的天文成果给予介绍 ,并讨论了自适应光学系统所能开展的天文研究课题。     

天文像复原迭代位移叠加法中初始信息的选择

给出了天文像复原“迭代位移叠加法”的第一步中确定位移基准点的方法-将目标像结构的初始信息与目标斑点图间的互相关性运算的极大值点作为基准点，按此基准点对目标斑点图进行位移叠加，第一步中初始信息的选择是展开迭代位移叠加过程的关键。讨论了目标初始信息的性质和提取方法。     

基于相位差方法的天文目标高分辨率成像研究

基于相位差方法的天文目标高分辨率成像,是利用在焦面和离焦位置上同时采集的一对或者多对短曝光图像,对目标和大气湍流引入的波前相位分布进行估计．在计算机模拟望远镜成像系统和相位差方法图像采集过程的基础上,利用信号估计和最优化理论,确定了高斯噪声模型下的目标函数,采用适合于大规模无约束优化的有限内存拟牛顿法对图像恢复问题进行了数值求解．恢复结果表明,基于相位差方法的高分辨成像技术,可以有效地克服大气湍流的影响,解决天文扩展目标的图像恢复问题．     

天文高分辨率像复原

本文以大气、望远镜和终端接收器组成的成像系统的分辨率的讨论为出发点,从傅里叶光学和统计光学观点阐明高分辨率天文像复原的确切含义,并按统一的思路讨论了几种典型的方法。最后对此领域的现状和发展进行了评论.     

天文斑点成象中的数据预处理

主要讨论了由云南天文台的斑点象探测系统引入斑点数据中的两种噪声：斑点图记录噪声和由大气视宁度差异引起的系统误差，叙述了用于克服噪声的预处理方法，噪声改正的实验结果表明：这些预处理对于实现天文目标的高分辨率象复原是有效的和必须的     

应用自适应光学望远镜所取得的天文观测成果

自适应光学技术已经成为现代地基天文学学肓远镜的重要部分。在世界各地的天文台中,许多大型光学望远镜的自适应光学系统正在建造,不少的系统已经投入使用。自适应光学技术经过二十多年的发展,取得了越来越多的令人激动的天文观测成果,自适应光学正在接近成熟并正向天文实际应用的阶段转化。本文根据近几年来自适应光学望远镜在天文中的应用,对其所取得的天文成果给予介绍,并讨论了自适应光学系统所能开展的天文研究课题。     

天文斑点成象中的数据预处理

主要讨论了由云南天文台的斑点象探测系统引入斑点数据中的两种噪声：斑点图记录噪声和由大气视宁度差异引起的系统误差，叙述了用于克服噪声的预处理方法，噪声改正的实验结果表明，这些预处理对于实现天文目标的高分辨率象复原是有效的和必须的。     

The hybrid energy spectrum of Telescope Array’s Middle Drum Detector and surface array

The Telescope Array experiment studies ultra high energy cosmic rays using a hybrid detector. Fluorescence telescopes measure the longitudinal development of the extensive air shower generated when a primary cosmic ray particle interacts with the atmosphere. Meanwhile, scintillator detectors measure the lateral distribution of secondary shower particles that hit the ground. The Middle Drum (MD) fluorescence telescope station consists of 14 telescopes from the High Resolution Fly’s Eye (HiRes) experiment, providing a direct link back to the HiRes measurements. Using the scintillator detector data in conjunction with the telescope data improves the geometrical reconstruction of the showers significantly, and hence, provides a more accurate reconstruction of the energy of the primary particle. The Middle Drum hybrid spectrum is presented and compared to that measured by the Middle Drum station in monocular mode. Further, the hybrid data establishes a link between the Middle Drum data and the surface array. A comparison between the Middle Drum hybrid energy spectrum and scintillator Surface Detector (SD) spectrum is also shown.     

The Data Flow, from Observations to the Archive: Simulating the Case of TNG

The telescopes of the new generation allow an archive to be built as a section of data management; nevertheless, careful planning is needed and data handling needs to be designed together with the control system of the telescope itself, both for space-borne and for ground-based facilities. Simulations are essential to understand how observations will be archived, and to build and test an archiving system capable of dealing efficiently with the expected data flow.The TNG (Telescopio Nazionale Galileo) will be one of the first ground-based observing facilities where archiving of both technical and scientific data will be made directly at the telescope as a natural extension of the data handling chain. The results obtained testing the prototype implementation of the archive system at the TNG with a simulated data flow will be shown.     

A quantitative treatment of solar ‘seeing’, I

Measurements of temperature-fluctuation statistics in a locally homogeneous, isotropic turbulent atmosphere above level land are shown to enable the quality of telescopic images of celestial objects to be calculated. Data obtained with captive-balloon-borne apparatus are used, together with other existing data, to calculate the modulation transfer function and Strehl Definition for both long- and short-exposure images formed by typical solar telescopes operating under a variety of meteorological conditions. The size of telescope may thus be matched to the expected atmospheric conditions; the improvement in performance and utilization of the instrument, obtainable by raising it on a tower, may be calculated. An 11-cm aperture telescope, for example, is shown to be atmosphere-limited for long exposures in average daytime conditions; raising it from 2 to 30 m above the ground makes an almost threefold improvement in definition. If observations are confined to intervals of good seeing the full resolution of such a telescope may be realized. The existence of such intervals is attributed to convective thermal structure in the atmosphere and observational statistics of periods of below-average temperature fluctuation are given for a range of general meteorological conditions.     

Adaptive Optics on Large Telescopes

Observations withground based telescopes suffer from atmospheric turbulence.Independent of the telescope size the angular resolution inthe visible is equivalent to that of a telescope with adiameter of 10–20 cm. This effect is caused by the turbulentmixing of air with different temperatures in the atmosphere.Thus, the perfect plane wave from a star at infinity isaberrated before it enters the telescope. In the following,we will discuss the physical background of imaging throughturbulence, using Kolmogorov statistics, and the differenttechniques to sense and to correct the wave-front aberrationswith adaptive optics. The requirements for the control loop ofan adaptive optics system are discussed including formulas forthe limiting magnitude of the guide star as a function of thewave-front sensing method, of the quality of the wave-frontsensor camera, and of the degree of correction. Finally, ashort introduction to deformable mirror technology will begiven followed by the presentation of a new method to measureand to distinguish individual turbulent layers in order toincrease the isoplanatic angle.     

图像移位堆叠方法用于暗天然卫星的天体测量

暗弱天然卫星与主带小行星相比,具有亮度低、速度变化快的特点.在观测这类天体时,不能简单地延长曝光时间来提高其信噪比.尝试观测多幅短曝光的CCD (chargecoupled device)图像,采用移位堆叠(shift-and-add)方法,希望提高目标成像的信噪比,获得暗弱天然卫星的精确测量结果.使用2018年4月9—12日夜间,中国科学院云南天文台1 m望远镜(1 m望远镜)拍摄的木星5颗暗卫星的229幅CCD图像,实施了移位堆叠试验.为了验证结果的正确性,与相近日期中国科学院云南天文台2.4 m望远镜(2.4 m望远镜)观测的相同木卫图像的测量结果进行了比较和分析.位置归算采用了JPL (Jet Propulsion Laboratory)历表.结果表明,对CCD图像使用移位堆叠方法,通过叠加约10幅曝光时间100 s的图像, 1 m望远镜能观测暗至19等星的不规则天然卫星,而且测量的准确度与2.4 m望远镜的测量结果有良好的一致性.     

Monte Carlo studies of medium-size telescope designs for the Cherenkov Telescope Array

We present studies for optimizing the next generation of ground-based imaging atmospheric Cherenkov telescopes (IACTs). Results focus on mid-sized telescopes (MSTs) for CTA, detecting very high energy gamma rays in the energy range from a few hundred GeV to a few tens of TeV. We describe a novel, flexible detector Monte Carlo package, FAST (FAst Simulation for imaging air cherenkov Telescopes), that we use to simulate different array and telescope designs. The simulation is somewhat simplified to allow for efficient exploration over a large telescope design parameter space. We investigate a wide range of telescope performance parameters including optical resolution, camera pixel size, and light collection area. In order to ensure a comparison of the arrays at their maximum sensitivity, we analyze the simulations with the most sensitive techniques used in the field, such as maximum likelihood template reconstruction and boosted decision trees for background rejection. Choosing telescope design parameters representative of the proposed Davies–Cotton (DC) and Schwarzchild–Couder (SC) MST designs, we compare the performance of the arrays by examining the gamma-ray angular resolution and differential point-source sensitivity. We further investigate the array performance under a wide range of conditions, determining the impact of the number of telescopes, telescope separation, night sky background, and geomagnetic field. We find a 30–40% improvement in the gamma-ray angular resolution at all energies when comparing arrays with an equal number of SC and DC telescopes, significantly enhancing point-source sensitivity in the MST energy range. We attribute the increase in point-source sensitivity to the improved optical point-spread function and smaller pixel size of the SC telescope design.     

Fast guiding and small telescopes in the 8-m era

Fast guiding may improve the images delivered by telescopes. It may be implemented fairly cheaply and offers an upgrade path to smaller telescopes, which will make them more useful in the 8-m era. However, the detailed performance of a fast guiding system must depend on many parameters and this makes it difficult to assess its precise scientific benefits. This paper provides a comprehensive mathematical framework for calculating the performance of fast guiding systems. A range of models has been calculated that illustrates the benefits for telescopes of various sizes in various wavelength ranges. Three measures of performance have been examined: FWHM, 50 per cent encircled energy diameter and energy concentration in a 0.35-arcsec aperture. Typical gains over natural seeing are found to be in the 20 to 40 per cent range at useful levels of sky coverage. Other things being equal, small telescopes do not benefit as much as large ones from fast guiding. The sensitivity of these benefits to assumptions has also been examined, and this highlights the need to operate in the correct wavelength range for the aperture in question. The largest perturbations to ideal models are likely to be the result of telescope windshake and the outer scale of turbulence. If there is appreciable windshake, fast guiding will yield larger benefits than expected from the natural seeing. A short outer scale (a few hundred metres) will, however, lose most of the gains.     

射电望远镜的发展和前景

在近代科学技术发展的基础上诞生和成长起来的射电天文学已经走过了66年的历程,作为射电天文学主要探测工具的射电望远镜有了长足的进步,面临21世纪人类社会和自然科学技术包括天文学发展的挑战,射电望远镜及射电天文学将迈出新的步伐．从射电天文学和射电望远镜发展的关系、射电望远镜几个主要发展方向和目前水平、自90年代以来逐步勾画而明确起来的未来发展方向等方面阐明了射电望远镜的发展和前景,以作为我国发展新一代射电望远镜的参考．