共查询到19条相似文献，搜索用时 203 毫秒
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讨论了经过大气后天文图象的象质衰减,研究了对这种衰减进行描述的视宁度参数ｒ０及其它几个大气光学参数,介绍了几种测量象质衰减参数的方法,重点介绍了我们将差分像运动法运用于白日视宁度测量的尝试以及新设计的可兼顾昼夜的视宁度测量仪,仪器已用于云台白日的视宁度测量。最后对近场近似假设进行了定量分析,在此基础上给出了新确定的近场近似成立的范围,这一范围比以前所给的要更大些。 相似文献
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大气视宁度是衡量台址大气光学品质的重要指标。差分像运动视宁度监测仪(Differential Image Motion Monitor,DIMM)被广泛应用于国内外天文选址的视宁度测量作业。介绍了一种优良的视宁度测量方法——差分像运动视宁度优化监测(Improved to Differential Image Motion Monitor,I-DIMM)法。首先对I-DIMM的结构设计和视宁度计算方法进行了详细描述;随后通过设置0. 36 m和0. 12 m两种口径望远镜进行视宁度的模拟测量,将I-DIMM测量结果与传统的DIMM测量的结果进行对比,均证明I-DIMM视宁度计算方法比DIMM更为精确;最后对模拟结果进行了分析,证明了I-DIMM相比于DIMM的优势。 相似文献
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讨论了经过大气后天文图象的象质衰减,研究了对这种衰减进行描述的宁度参数ｒ０及其它几个大气光学参数,介绍了几种测量象质衰减参数的方法,重点介绍了我们将差分像运动法运用于白日视宁度测量的尝试以及新设计的可兼顾昼夜的视宁度测量仪,仪器已用于云台白日的视宁度测量。最后对近场近似假设进行了定量分析,在此基础上给出新确定的近场近似成立的范围,这一范围比以前所给的要更大些。 相似文献
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《天文研究与技术》2020,(2)
圆顶引起望远镜附近的大气湍流,造成望远镜成像质量与观测精度下降,较差的圆顶视宁度浪费了优秀台址的观测条件。圆顶通风是大型望远镜圆顶设计中必不可少的部分,可以有效解决圆顶视宁度问题。为了减小兴隆2.16 m望远镜圆顶视宁度对观测的影响,将圆顶吊装通道改造为通风口,并使用计算流体动力学软件对通风效果进行分析。分析结果表明,将圆顶吊装通道改造为通风口可以提高圆顶内外热平衡速率,使圆顶内空气更稳定,从而降低圆顶视宁度对观测的影响。根据通风效果模拟结果,可对通风策略进行优化设计。圆顶通风的研究可为2.16 m望远镜圆顶通风改造提供参考依据,以提高望远镜成像质量和观测效率。 相似文献
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白日视宁度监测仪和在抚仙湖的初步观测结果 总被引：1，自引：1，他引：0
报导了用南方基地云南天文台太阳差分像运动视宁度监测仪和美国国立太阳天文台的太阳闪烁仪,在云南省澄江县抚仙湖老鹰地红外太阳塔选址点进行的对比观测,简要地介绍了这两种视宁度测量方法的原理,对观测的初步结果进行了分析。 相似文献
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Jacques M. Beckers 《Experimental Astronomy》2001,12(1):1-20
In this article I describe a site survey facility, which measures the signals of the solar equivalent of a Differential Image Motion Monitor (S-DIMM) and of a six element linear array of solar scintillometers. Combining the S-DIMM r
o andscintillometer I observations allows the determination of the fractions of the seeing in the free atmosphere and in the ground/lake layer. From the scintillometer array observations C
n
2
(h) is determined for heights corresponding to the first 500 m along the line-of-sight. With minor changes this seeing monitor can also be used for other extended objects like the Moon and planets. 相似文献
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Jagdev Singh 《Journal of Astrophysics and Astronomy》2008,29(1-2):345-351
Sun’s atmosphere is an ideal place to study and test many magnetohydrodynamic (MHD) processes controlling turbulent plasma. We wish to resolve some of the finest solar features (which remain unresolved presently) and study their dynamics. Indian Institute of Astrophysics has proposed to design, fabricate and install a 2-meter class solar telescope at a suitable site in India to resolve features on the Sun of the size of about 0.1 arcsec. The focal plane instruments will include a high resolution polarimeteric package to measure polarization with an accuracy of 0.01 per cent; a high spectral resolution spectrograph to obtain spectra in 5 widely separated absorption lines simultaneously and high spatial resolution narrow band imagers in various lines. The Himalayan region appears to be a good choice keeping in view the prevailing dry and clear weather conditions. We have started detailed analysis of the weather conditions in the area and at some other locations in India. The site characterization will be done using the Sun-photometer, S-DIMM and SHABAR techniques to determine the seeing conditions. 相似文献
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Starting November 1999 we are carrying out simultaneous seeing observations with the Solar Differential Image Motion Monitor (S-DIMM) at the Fuxian Lake station of the Yunnan Observatory and a solar scintillometer of the type used in the recent site survey by one of us (Beckers et al., 1997). The purpose was to compare the two methods of assessing the daytime atmospheric seeing for a lake site. We report here the first results of this comparison. We find that the relation between the seeing as measured by the S-DIMM (the Fried parameter r
0) and the scintillation in the solar irradiance (I) differs greatly from the relation found by Seykora (1993) for NSO/Sac Peak. We conclude that the I measurements give a good indication for the amount of near-Earth seeing but that they are a poor proxy for the total atmospheric seeing. We interpret the simultaneous (r
0, I) observations in terms of an atmospheric seeing model and find good quantitative agreement with a model in which a fraction () of the seeing originated near the Earth (ground or water) and the rest (1–) originates at higher layers. For lake sites is small all day and the seeing is determined primarily by the refractive index variations at higher atmospheric layers. For land sites is small in the early morning but rapidly increases as the day progresses, near-Earth seeing dominating there most of the time. 相似文献
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We present an implementation of the extended Knox-Thompson (EKT) speckle reconstruction algorithm dedicated to solar observations.
EKT speckle imaging yields nearly diffraction-limited images from bursts of short exposure solar observations under a wide
range of seeing conditions. Our implementation supports field dependent amplitude calibration to permit analyzing data obtained
with a partially compensating adaptive optics systems. The principles of the method and some technical details of our implementation
are discussed. We have performed various tests using simulated data of representative solar scenes. The simulations include
the effects of seeing and noise with the exception of anisoplanatism. The expected photometric error of a reconstructed image
amounts to a few percent of the mean intensity under seeing conditions ranging from poor to excellent. We also present sample
reconstructions of real data and discuss issues arising from anisoplanatism. 相似文献
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New vacuum solar telescope and observations with high resolution 总被引：1，自引：0，他引：1
Zhong Liu Jun Xu Bo-Zhong Gu Sen Wang Jian-Qi You Long-Xiang Shen Ru-Wei Lu Zhen-Yu Jin Lin-Fei Chen Ke Lou Zhi Li Guang-Qian Liu Zhi Xu Chang-Hui Rao Qi-Qian Hu Ru-Feng Li Hao-Wen Fu Feng Wang Men-Xian Bao Ming-Chan Wu Bo-Rong Zhang 《天文和天体物理学研究(英文版)》2014,(6):705-718
The New Vacuum Solar Telescope(NVST) is a one meter vacuum solar telescope that aims to observe fine structures on the Sun. The main goals of NVST are high resolution imaging and spectral observations, including measurements of the solar magnetic field. NVST is the primary ground-based facility used by the Chinese solar research community in this solar cycle. It is located by Fuxian Lake in southwest China, where the seeing is good enough to perform high resolution observations. We first introduce the general conditions at the Fuxian Solar Observatory and the primary science cases of NVST. Then, the basic structures of this telescope and instruments are described in detail. Finally, some typical high resolution data of the solar photosphere and chromosphere are also shown. 相似文献
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We present a detailed thermal and structural analysis of a 2 m class solar telescope mirror which is subjected to a varying heat load at an observatory site. A 3-dimensional heat transfer model of the mirror takes into account the heating caused by a smooth and gradual increase of the solar flux during the day-time observations and cooling resulting from the exponentially decaying ambient temperature at night. The thermal and structural response of two competing materials for optical telescopes, namely Silicon Carbide – best known for excellent heat conductivity and Zerodur – preferred for its extremely low coefficient of thermal expansion, is investigated in detail. The insight gained from these simulations will provide a valuable input for devising an efficient and stable thermal control system for the primary mirror. 相似文献
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光度特性测量是获取空间目标的物理特性的重要技术手段之一,无论是光变曲线的事后分析还是建立光度变化的仿真模型,都离不开一个重要的参数——太阳相位角（太阳-空间目标-测站的空间夹角）.目前空间目标的位置通常是通过双行根数（TLE）外推获得,存在一定误差,且随外推时间的延长而变大,因而有必要对其计算所得的太阳相位角的精度进行评估.以典型的不同高度的激光测距卫星LAGEOS1、AJISAI、STELLA为研究对象,以全球激光测距资料解算所得的高精度轨道作为参考轨道,对2012年全年利用双行根数计算所得的太阳相位角数据进行了比对分析,结果表明对于LAGEOS1、AJISAI这样的中高轨卫星,由于轨道较高,表征阻力的B＊恒定,计算所得的太阳相位角偏差较小,角分量级,且随外推时间的延长不会导致偏差明显增大;而对于STELLA这样的低轨卫星,因轨道较低、受变化的大气的影响显著,计算所得的太阳相位角偏差较大,尤其是当B＊比较大、变化较快时,偏差显著变大,且随外推时间的延长显著增大,在最差情况下：外推1d约为13＇,外推3d约为50＇,外推7d约为251＇,已超出目前的精度要求.因此,在事后分析中应尽可能使用1d之内的TLE计算太阳相位角,对于B＊较大且变化较快情况尤其需要注意.另外,针对UTC闰秒的情况,提出了一种处理方法,即在双行根数外推时判断外推时段是否跨越了闰秒时刻,若跨越了则进行修正：增加或减少1s,相应地需要修改结果对应的时间戳计算方法. 相似文献
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Rennan Barkana 《Monthly notices of the Royal Astronomical Society》2009,397(3):1454-1463
We explore the ability of measurements of the 21-cm power spectrum during reionization to enable the simultaneous reconstruction of the reionization history and the properties of the ionizing sources. For various sets of simulated 21-cm observations, we perform maximum likelihood fits in order to constrain the reionization and galaxy formation histories. We employ a flexible six-parameter model that parametrizes the uncertainties in the properties of high-redshift galaxies. The computational speed needed is attained through the use of an analytical model that is in reasonable agreement with numerical simulations of reionization. We find that one-year observations, with the Murchison Widefield Array, should measure the cosmic ionized fraction to ∼1 per cent accuracy at the very end of reionization, and a few per cent accuracy around the mid-point of reionization. The mean halo mass of the ionizing sources should be measurable to 10 per cent accuracy when reionization is 2/3 of the way through, and to 20 per cent accuracy throughout the central stage of reionization, if this mass is anywhere in the range 1/3 to 100 billion solar masses. 相似文献
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The daytime atmospheric turbulence profile is crucial for the design of both optical systems and the control algorithm of a solar Multi-Conjugate Adaptive Optics(MCAO) system. The Multi-Aperture Seeing Profiler(MASP) is a portable instrument which can measure the daytime turbulence profile up to~30 km. It consists of two portable small telescopes that can deliver performance similar to a SolarDifferential Image Motion Monitor +(S-DIMM+) on a 1.0 m solar telescope. In the original design of MASP, only two guide stars are used to retrieve the turbulence profile. In this paper, we studied the usage of multiple guide stars in MASP using numerical simulation, and found that there are three main advantages.Firstly, the precision of the turbulence profile can be increased, especially at a height of about 15 km, which is important for characterizing turbulence at the tropopause. Secondly, the equivalent diameter of MASP can be increased up to 30%, which will reduce the cost and weight of the instruments. Thirdly, the vertical resolution of the turbulence profile near the ground increases with the help of multiple guide stars. 相似文献