共查询到20条相似文献，搜索用时 31 毫秒
1.
Nian-Ping Liu Yu Liu Yun-Deng Shen Xue-Fei Zhang Wen-Da Cao Jean Arnaud 《Chinese Astronomy and Astrophysics》2011,35(4):428
A modern aureole photometer (AP) was developed for the site survey inWest China, in preparation for the installation of future large solar equipments. The performance of this new AP was tested in preliminary observations, and a lot of sky brightness data were accumulated at a few sites in Yunnan Province. The result of data analysis shows that the aureole near the noon time on Jiaozi Snow Mountain is as low as a few millionths of the intensity at the solar disk center, indicating the low internal stray light level of our instrument. The internal stray light of the AP comes mainly from two parts: the edge diffraction of the ferrule for fixing the ND4 filter in the front end of the telescope tube, causing the stray light distributed in the inner region of the field of view, and the edge diffractions of the diaphragms placed inside the telescope tube, causing the stray light distributed in the outer region of the field of view. In order to suppress the stray light of the latter part, the experiment to change the aperture size of an additional diaphragm was performed. The result shows that the stray light in the outer region of the field of view can be effectively suppressed by reducing properly the aperture size of the diaphragm. 相似文献
2.
To achieve high spatial resolution capability for IR solar observations, we suggest the use of a special mask placed before the entrance aperture of large conventional optical telescopes. Such a mask would match well the resolution of a non-redundant array and would provide safe operation of a large telescope used for solar observations. The proposed solution has the additional advantage of relatively low cost because already-existing optical telescopes are used. 相似文献
3.
We present a detailed model of stray-light suppression in the spectrometer channels of the Ultraviolet Coronagraph Spectrometer (UVCS) on the SOHO spacecraft. The control of diffracted and scattered stray light from the bright solar disk is one of the most important tasks of a coronagraph. We compute the fractions of light that diffract past the UVCS external occulter and non-specularly pass into the spectrometer slit. The diffracted component of the stray light depends on the finite aperture of the primary mirror and on its figure. The amount of non-specular scattering depends mainly on the micro-roughness of the mirror. For reasonable choices of these quantities, the modeled stray-light fraction agrees well with measurements of stray light made both in the laboratory and during the UVCS mission. The models were constructed for the bright H i Lyα emission line, but they are applicable to other spectral lines as well. 相似文献
4.
Shu-Mo Gong 《Astrophysics and Space Science》1986,118(1-2):15-20
This paper covers the main aspects of three new optical telescopes: a 1.26 m aperture one for use in the infrared, a 1.56 m aperture one for astrometry, and a 2.16 m reflector for general astrophysical work. It also briefly mentions the 13.7 m telescope designed for the mm wavelength band, the first VLBI in China and the meter wavelength aperture synthesis telescope. All these telescopes, optical and radio, are now being built in China.Paper presented at the IAU Third Asian-Pacific Regional Meeting, held in Kyoto, Japan, between 30 September–6 October, 1984. 相似文献
5.
There is a disconcerting global trend of retiring telescopes of modest aperture, supplanting them instead with fewer expensive telescopes of quite large aperture. As a consequence, the available time and feasibility of following transient objects in astrophysics is diminishing. We show the utility of having a suite of small to moderate aperture telescopes capable of conducting imaging and spectroscopic observations in a service queue mode. The example we provide is the high-cadence early observations of the classical nova V475 Scuti (2003) carried out with the SMARTS suite of telescopes located at CTIO. 相似文献
6.
Martin Nekola René Hudec Martin Jelínek Matůš Kocka Petr Kubánek Filip Münz Cyril Polášek Vojtěch Šimon Jan Štrobl 《Experimental Astronomy》2010,28(1):79-85
We report on two small aperture robotic telescopes called BART and D50 operated in Ondřejov. Both telescopes are capable of
automatic observation of gamma ray burst (GRB) optical afterglows. Coordinates of GRBs are taken from alerts distributed via
Internet. Telescopes observe other interesting high energy sources when there is not any alert. The smaller telescope BART
has aperture D = 254 mm. The bigger telescope D50 has a primary mirror of diameter D = 500 mm. Both telescopes are controlled
by free software package RTS2 and are accessible through Internet. We describe the two telescopes and related software and
show some results such as our first observed optical counterpart of GRB. 相似文献
7.
P. von Ballmoos 《Experimental Astronomy》1995,6(4):85-96
Gamma-ray lines are the fingerprints of nuclear transitions, carrying the memory of high energy processes in the universe. Setting out from what is presently known about line emission in gamma-ray astronomy, requirements for future telescopes are outlined. The inventory of observed line features shows that sources with a wide range of angular and spectral extent have to be handled: the scientific objectives for gamma-ray spectroscopy are spanning from compact objects as broad class annihilators, over longlived galactic radioisotopes with hotspots in the degree-range to the extremely extended galactic disk and bulge emission of the narrow e– e+ line.The instrumental categories which can be identified in the energy range of nuclear astrophysics have their origins in the different concepts of light itself: geometrical optics is the base of modulating aperture systems-these methods will continue to yield adequate performances in the near future. Beyond this, focusing telescopes and Compton telescopes, based on wave- and quantum- optics respectively, may be capable to further push the limits of resolution and sensitivity. 相似文献
8.
I. A. Ipatova A. G. Mikhailov V. V. Mardyshkin M. A. Kharinov 《Solar System Research》2006,40(2):169-173
The possibilities of using the RTF-32 radio telescopes of the interferometric QUASAR network for solar observations are investigated. A technique of solar radio mapping with the RTF-32 telescopes is presented. The software developed at the Institute of Applied Astronomy, Russian Academy of Sciences, for reducing such observations is described. The maps of the Sun at 1.35 cm, derived from observations at the Zelenchukskaya observatory November 4–14, 2004, are presented. 相似文献
9.
10.
V. P. Aleshin E. A. Grishin O. A. Ivlev D. D. Novgorodtsev V. D. Shargorodsky 《Kinematics and Physics of Celestial Bodies》2016,32(5):255-259
Telescopes with aperture higher than 3 m and with travel rate of optical axis of more than 4 angular degrees per second are examined. These telescopes are used for estimating the situation in near-Earth space. Up to now, there are three telescopes with such parameters: SOR, AMOS, SST (all in the United States). A telescope of the same class with aperture of 3.12 m (information telescope TI-3.12) is under completion at Altai Optical Laser Center. The main technical performances of the TI-3.12 telescope are described in the paper. Current problems are defined and ways for their solution are presented. 相似文献
11.
K. S. Gothe T. P. Prabhu P. R. Vishwanath B. S. Acharya R. Srinivasan V. R. Chitnis P. U. Kamath G. Srinivasulu F. Saleem P. M. M. Kemkar P. K. Mahesh F. Gabriel J. Manoharan N. Dorji T. Dorjai D. Angchuk A. I. D’souza S. K. Duhan B. K. Nagesh S. K. Rao S. K. Sharma B. B. Singh P. V. Sudersanan M. Tashi Thsering S. S. Upadhya G. C. Anupama R. J. Britto R. Cowsik L. Saha A. Shukla 《Experimental Astronomy》2013,35(3):489-506
An array of seven atmospheric Cherenkov telescopes was commissioned at a high altitude site in Hanle in the Ladakh region of the Himalayas. The array called HAGAR has been designed to observe celestial γ-rays of energy >100 GeV. Each telescope is altitude-azimuth mounted and carries seven parabolic mirrors whose optic axes are co-aligned with the telescope axis. The telescopes point and track a celestial source using a PC-based drive control system. Two important issues in positioning of each HAGAR telescope are pointing accuracy of telescope axis and co-alignment of mirrors’ optic axes with the telescope axis. We have adopted a three pronged strategy to address these issues, namely use of pointing models to improve pointing accuracy of the telescopes, RA-DEC scan technique to measure the pointing offsets of the mirrors and mechanical fine-tuning of off-axis mirrors by sighting a distant stationary light source. This paper discusses our efforts in this regard as well as the current status of pointing and monitoring of HAGAR telescopes. 相似文献
12.
Well sampled light curves of BL Lac objects are very useful to understand the physical processes responsible for the highly
variable emission from this class of AGN. The best way to perform the necessary high number of observations is the use of
automatic small aperture telescopes. We present some results of the Perugia-Roma monitoring program concerning the recent
active phase of BL Lac and the Intra-Day Variability of S5 0716+714.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
13.
A. Bianco C. Bertarelli M. C. Gallazzi G. Zerbi E. Giro E. Molinari 《Astronomische Nachrichten》2005,326(5):370-374
Modern astronomical spectroscopy makes use of multi‐aperture slits placed in the focal plane of telescopes before light enters the spectrograph. Multiple object spectroscopy (MOS) allows several spectra to be obtained simultaneously with a multiplexing gain from the order of dozens of objects in 4m class telescopes to few hundreds in larger 8 m telescopes. Many of these devices make use of metal plates which are punched, milled or laser cut and can be used only for observation of a given astronomical target. A typical observing night requires from 4 to 20 MOS masks, which have to be prepared during an off‐line procedure, usually days before. Here we report an innovative technique to carry out multi object spectroscopy based on changes of properties of photochromic materials. Photochromic MOS masks consist of polymer thin films which can be made opaque or transparent in a restricted wavelength range using alternatively UV and visible light. Slit patterns can thus be easily written by means of a red diode laser on a UV preflashed plate. Writing time for a 10 × 10 arcmin plate is a few minutes and the whole procedure can be performed promptly after the acquisition of the field image and without mechanical debris as in milling or laser cutting. A computer controlled writing device suited for the AFOSC camera of the Asiago 1.8m telescope was built. The same focal plane mask can be UV erased and used more than 450 times. High contrasts have been reached by means of an appropriate passband filter in the light beam of the spectrograph. Our first successful observation run took place in January 2003. Spectra of selected stars in the crowded M67 cluster field and emission lines from the gaseous planetary nebula M97 were obtained. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
14.
Rolf Brahde 《Solar physics》1972,26(2):318-334
A numerical method for correction of stray light in solar observations has been developed. In particular a regular sunspot, where the circular contours of penumbra and umbra are projected as ellipses, has been studied. When a specified set of values for the stray light parameters is given, and also tentative values for the relative intensities of penumbra and umbra, the integration of stray light can be performed in any point. The result will be the observable intensity if the conditions were as given by these initial values.By means of limb observations the stray light parameters may be improved, and finally a variation of the penumbra- and umbra intensities in the computation, enables a determination of these quantities by comparison with observations.The method is tested on observations of the transit of Mercury, May 9, 1970. Calculation of isophotes with Mercury close to the limb shows the black drop phenomenon; which thus may be explained as an effect of stray light only.It is also shown that the Wilson effect on a sunspot cannot be produced by stray light alone. 相似文献
15.
Dainis Dravins Stephan LeBohec Hannes Jensen Paul D. Nuñez 《New Astronomy Reviews》2012,56(5):143-167
Using kilometric arrays of air Cherenkov telescopes at short wavelengths, intensity interferometry may increase the spatial resolution achieved in optical astronomy by an order of magnitude, enabling images of rapidly rotating hot stars with structures in their circumstellar disks and winds, or mapping out patterns of nonradial pulsations across stellar surfaces. Intensity interferometry (once pioneered by Hanbury Brown and Twiss) connects telescopes only electronically, and is practically insensitive to atmospheric turbulence and optical imperfections, permitting observations over long baselines and through large airmasses, also at short optical wavelengths. The required large telescopes (～10 m) with very fast detectors (～ns) are becoming available as the arrays primarily erected to measure Cherenkov light emitted in air by particle cascades initiated by energetic gamma rays. Planned facilities (e.g., CTA, Cherenkov Telescope Array) envision many tens of telescopes distributed over a few square km. Digital signal handling enables very many baselines (from tens of meters to over a kilometer) to be simultaneously synthesized between many pairs of telescopes, while stars may be tracked across the sky with electronic time delays, in effect synthesizing an optical interferometer in software. Simulated observations indicate limiting magnitudes around mV = 8, reaching angular resolutions ～30 μarcsec in the violet. The signal-to-noise ratio favors high-temperature sources and emission-line structures, and is independent of the optical passband, be it a single spectral line or the broad spectral continuum. Intensity interferometry directly provides the modulus (but not phase) of any spatial frequency component of the source image; for this reason a full image reconstruction requires phase retrieval techniques. This is feasible if sufficient coverage of the interferometric (u, v)-plane is available, as was verified through numerical simulations. Laboratory and field experiments are in progress; test telescopes have been erected, intensity interferometry has been achieved in the laboratory, and first full-scale tests of connecting large Cherenkov telescopes have been carried out. This paper reviews this interferometric method in view of the new possibilities offered by arrays of air Cherenkov telescopes, and outlines observational programs that should become realistic already in the rather near future. 相似文献
16.
Over the last few years, several interesting observations were obtained with the help of solar Adaptive Optics (AO). In this paper, few observations made using the solar AO are enlightened and briefly discussed. A list of disadvantages with the current AO system are presented. With telescopes larger than 1.5 m expected during the next decade, there is a need to develop the existing AO technologies for large aperture telescopes. Some aspects of this development are highlighted. Finally, the recent AO developments in India are also presented. 相似文献
17.
苏定强 《紫金山天文台台刊》2003,(1)
目前 ,已有 1 0架口径 8～ 1 0m的地面大望远镜建成并投入科学观测。在近红外波段 ,自适应光学和干涉术已在大望远镜上获得成功。Hubble空间望远镜发射至今已逾 1 2年。为了研究早期宇宙 ,探测类地行星等 ,2 0 0 2年 9月NASA已与TWR公司签约 ,研制口径≥ 6m的下一代空间望远镜JWST ,计划2 0 1 0年发射。许多口径 30～ 1 0 0m的地面未来巨型望远镜FGT项目已经提出。本报告 ,也介绍了我国正在研制或预研中的三个大项目 :LAMOST、FAST和SST ,这些项目虽较小 ,但完成后都会对天文学的一个方面作出有份量的贡献。最后 ,报告人建议我国参与到与国外合作研制FGT或NGST的工作中 ,特别强调要有天文学家和工程专家参与进去 相似文献
18.
19.
Jenkins 《Monthly notices of the Royal Astronomical Society》1998,294(1):69-92
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. 相似文献
20.
Adriana Valio P. Kaufmann C. G. Giménez de Castro J.-P. Raulin L. O. T. Fernandes A. Marun 《Solar physics》2013,283(2):651-665
We present a new system of two circular polarization solar radio telescopes, POEMAS, for observations of the Sun at 45 and 90 GHz. The novel characteristic of these instruments is the capability to measure circular right- and left-hand polarizations at these high frequencies. The two frequencies were chosen so as to bridge the gap at radio frequencies between 20 and 200 GHz of solar flare spectra. The telescopes, installed at CASLEO Observatory (Argentina), observe the full disk of the Sun with a half power beam width of 1.4°, a time resolution of 10 ms at both frequencies, a sensitivity of 2?–?4 K that corresponds to 4 and 20 solar flux unit (=104 Jy), considering aperture efficiencies of 50±5 % and 75±8 % at 45 and 90 GHz, respectively. The telescope system saw first light in November 2011 and is satisfactorily operating daily since then. A few flares were observed and are presented here. The millimeter spectra of some flares are seen to rise toward higher frequencies, indicating the presence of a new spectral component distinct from the microwave one. 相似文献