共查询到20条相似文献，搜索用时 156 毫秒
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弧分和弧秒──易误解的单位广东读者蔡明问，在天文学中“弧秒”是不是“弧度”的六六？天文学中常以“角分”和“角秒”为单位来表示微小角度的大小。例如，太阳和月亮的角直径常用“角分”表示；恒星和行星的角直径、双星系统中两子星的角距离、天体引力产生的光线的偏... 相似文献
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根据对河外射电源3C454.3第二历元327MHz的VLBI观测数据的多分量模型拟合，得到该源5个分量的模型拟合结构。该结构的尺度从几百毫角秒延伸到几个角秒。与Merlin的观测结果比较，有迹象表明存在一个新的分量C4。 相似文献
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译文:从地球上看,月球的视直径为31′,在口径40cm,焦距254cm的望远镜的焦面上所成月像的直径是多少?画图解释你的计算。 解答:对于焦距为F(单位为mm)的望远镜,其焦面上的线尺寸l与对应的天空张角α之间的关系为:l=Ftgα,当α较小时,有l≈Fα,当l取毫米作单位,α取角秒作单位时,有l=Fα″sin1″,由上式可得望远镜的底 相似文献
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使用一具附有测微器的光学望远镜配合赤道式射电望远镜进行极轴精密调整,不需用精确的度盘和记时设备。极轴测量和校准精度可达6角秒左右。本文详细叙述了这种方法的测量原理和操作步骤。 相似文献
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目目特(MMT)原来是多镜面望远镜的意思。它位于亚利桑纳州图桑市南60千米的霍普金斯山顶。在1974年建成时,它由6个跨径1.8米的正六边形镜面组合成等效口径4.5米的一架望远镜。但是在1985年,研究人员们决定将它改建成一架由一个口径6.5米的主镜构成的单口径望远镜。改建后不仅可以使聚光本领加倍,而且可以把角视场加大到15倍。1998年3月2日,它停止了观测并被拆卸了。1998年8月6日,安装了能够支承口径6.5米主镜的镜室。1999年3月25日,由施蒂瓦尔德天文台镜面实验室浇 相似文献
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“高于角秒分辨率的射电天文学会议”于1992年7月20—24日在英国曼彻斯特大学召开,它是由该校所属的Nuffield射电天文实验室主办的。该会议受到剑桥大学出版社,皇家天文协会,曼彻斯特大学,Interferometrics Inc.(美国),MAN(德国),URSI,皇家协会等8个单位的资助。 会议集中讨论利用HST哈勃空间望远镜), 相似文献
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TM65 m射电望远镜指向模型的建立 总被引：1，自引：0，他引：1
《天文学报》2015,(2)
介绍了建立上海天文台天马65 m射电望远镜(简称TM65 m)指向模型的过程.采用"十字扫描"的方法对单点数据进行采集,采用带有高斯项和非线性项的曲线模型进行偏差拟合,并对单点扫描过程中源角径导致的波束展宽量进行了仿真分析,通过使用射电源预报来提高建立模型的效率.用最小二乘法对全天区数据进行拟合,得出了8个天线参数的指向模型,并在实际中验证,最后建立了TM65 m望远镜X波段指向模型.盲指误差达到12.36角秒,满足了X波段及以下波段的指向要求. 相似文献
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对于用佘山40厘米折射望远镜拍摄的10组底片，用底片常数法和中心重叠法分别重新作了归算；对于饮食大时角底片的组，归算中使用在恒星常数中加进折射项的办法计入了大气色散改正。给出了15颗星的相对视和自行，以及由重叠解换算的绝对视差，对视差测定值的精度作了讨论。 相似文献
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William A. Sloan 《Solar physics》1968,5(3):329-337
The intensity of the sun was measured in the Lyman- emission line with 2.5 arc-seconds of resolution. The experiment was flown in an Aerobee-150 rocket on April 28, 1966. It contained a Cassegrain telescope with a pinhole aperture placed at the focus followed by a gas-gain ionization chamber whose spectral response was 1050 Å to 1350 Å.An isophote map 1.5 by 3 arc-minutes in size made from a composite of 90 linear scans shows an enhanced region and adjacent to it a prominent dark lane 20 arc-seconds wide. The measured intensity ratio of these two regions is nine. Bright features between 6 and 20 arc-seconds in size showed typical peak intensities of 20% greater than the surrounding chromosphere. The smallest features observed were 2.5 arc-seconds in size. A direct measurement of the absolute intensity at 1216 Å gave a value of 5.9 × 104 erg cm–2 s–1 sterad–1 in the quiet chromosphere.Based on observations made by the author at the E. O. Hulburt Center for Space Research (supported jointly by the Office of Naval Research and the National Science Foundation) at the Naval Research Laboratory. 相似文献
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Roland Vanderspek John P. Doty Geoffrey B. Crew George R. Ricker 《Astrophysics and Space Science》1995,231(1-2):483-486
The High Energy Transient Experiment (HETE) will be able to perform multiwavelength observations of-ray and X-ray bursts. HETE will potentially be able to localize-ray bursts to a precision of 20 arc-minutes if significant X-ray flux is detected from the burst; a precision of 20 arc-seconds is possible if there is also significant UV radiation from the burst. HETE will broadcast information about bursts detected within seconds of their detection. This VHF-band broadcast will be received at a number of secondary ground stations (SGS) dedicated to HETE, and forwarded to a central distribution site at MIT, from which it is sent to interested observers via Internet. 相似文献
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天王星卫星的CCD观测与分析解的比对 总被引：2，自引：0，他引：2
本文给出了处理天王星卫星ＣＣＤ图象位置资料的新方法,并将我们在１９９５年取得的重要资料与两种理论模型位置进行了比较计算,结果表明经处理后的天王星五颗主要卫星ＣＣＤ观测精度有了较大提高。 相似文献
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Yasunori Fujiwara Yoshiyuki Hamaguchi Takuji Nakamura Masaki Tsutsumi Makoto Abo 《Earth, Moon, and Planets》2008,102(1-4):309-314
The MU radar of RISH (Research Institute for Sustainable Humanosphere, Kyoto University), which is a MST radar (46.5 MHz,
1 MW peak power), has been successfully applied to meteor studies by using its very high versatility. The system has recently
renewed with 25 channel digital receivers which significantly improved the sensitivity and precision of interferometer used
in meteor observation. The transmission is now synchronized to GPS signals, and two external receiving sites with a ranging
capability has additionally been operated in order to determine the trajectories and speeds of meteoroids. 相似文献
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利用新发表的高精度、高密度天体测量星表UCAC2,对天王星的五颗主要卫星的CCD观测图像重新进行量测,采用不同方法作定标归算,并使用两种理论模型(GUST86和GUST06模型)计算卫星的理论位置。对不同方法所得到的卫星位置的O-C结果的分析和比较表明,本文获得的卫星位置精度,除天卫五(Miranda)有显著提高,其他4颗卫星的位置精度基本相同。本文中天卫一和天卫三的结果与"亮卫星定标法"的结果在精度上相当,天卫二的位置精度与其他天王星卫星的位置精度具有较好的一致性,这从另一方面证明了我们的"亮卫星定标法"的可靠性。此外我们还获得了天卫四的位置与精度。 相似文献
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JØrgen Christensen-Dalsgaard 《Solar physics》2004,220(2):137-168
The physics of solar and stellar oscillations determines their observable properties: frequencies, amplitudes, lifetimes,
line asymmetries and phase relations. In the solar case these quantities have been measured, often with high precision, and
much has been learned about the properties of the solar interior, and the properties of the oscillations. With recent advances
in observational techniques, such seismic investigations are now being extended to solar-like oscillations in distant stars.
I provide a brief overview of the basic properties of stellar oscillations, and of the information about stellar properties
that may be inferred from them, concentrating mostly on the low-degree modes for which information may be expected for distant
stars. In addition, I consider the current state of investigations of solar-like oscillations in other stars, and the prospects
for an improved understanding of the physics of such oscillations. 相似文献
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Shu Zhang 《Chinese Astronomy and Astrophysics》1998,22(4):419-422
The COMPTEL observation of the γ-ray burst GRB 910601 has been reanalyzed using a direct demodulation method. The imaging result indicates that the location of GRB 910601 is closer to the annulus obtained by the Ulysses-BATSE system than that with the maximum-likelihood method. This confirms the feasibility of processing γ-ray bursts, a kind of transient source with good signal-to-noise ratio but poor statistics, with a direct demodulation method. The precision of locating γ-ray bursts by imaging can also be improved using this method. 相似文献
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Accurate Mars Express orbits to improve the determination of the mass and ephemeris of the Martian moons 总被引：1，自引：0，他引：1
P. Rosenblatt V. Lainey S. Le Maistre J.C. Marty V. Dehant M. Ptzold T. Van Hoolst B. Husler 《Planetary and Space Science》2008,56(7):1043-1053
The determination of the ephemeris of the Martian moons has benefited from observations of their plane-of-sky positions derived from images taken by cameras onboard spacecraft orbiting Mars. Images obtained by the Super Resolution Camera (SRC) onboard Mars Express (MEX) have been used to derive moon positions relative to Mars on the basis of a fit of a complete dynamical model of their motion around Mars. Since, these positions are computed from the relative position of the spacecraft when the images are taken, those positions need to be known as accurately as possible. An accurate MEX orbit is obtained by fitting two years of tracking data of the Mars Express Radio Science (MaRS) experiment onboard MEX. The average accuracy of the orbits has been estimated to be around 20–25 m. From these orbits, we have re-derived the positions of Phobos and Deimos at the epoch of the SRC observations and compared them with the positions derived by using the MEX orbits provided by the ESOC navigation team. After fit of the orbital model of Phobos and Deimos, the gain in precision in the Phobos position is roughly 30 m, corresponding to the estimated gain of accuracy of the MEX orbits. A new solution of the GM of the Martian moons has also been obtained from the accurate MEX orbits, which is consistent with previous solutions and, for Phobos, is more precise than the solution from the Mars Global Surveyor (MGS) and Mars Odyssey (ODY) tracking data. It will be further improved with data from MEX-Phobos closer encounters (at a distance less than 300 km). This study also demonstrates the advantage of combining observations of the moon positions from a spacecraft and from the Earth to assess the real accuracy of the spacecraft orbit. In turn, the natural satellite ephemerides can be improved and participate to a better knowledge of the origin and evolution of the Martian moons. 相似文献