Optimal Baffle Design in a Cassegrain Telescope

An exact analytical procedure is described for the optimum design of baffles for any Cassegrain telescope with conicoid type mirrors. Here, `optimum' means the least obstruction coefficient given perfect blocking of direct light by baffles. The corresponding algorithm is based on the ray-tracing formulas in a two-mirror telescope with arbitrary position of the aperture stop. The optimal configuration of baffles is unique. The dependence of the obstruction coefficient upon the telescope characteristics is studied. The optical system can be designed in such a way that the obstruction is equal to a predefined value. As examples, the Hubble Space Telescope and the Ritchey–Chretien system with the obstruction coefficient 0.25 are considered.     

New telescopes in China

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.     

Optimal Baffle Design in a Cassegrain Telescope

An exact analytical procedure is described for the optimum design of baffles for any Cassegrain telescope with conicoid type mirrors. Here, `optimum' means the least obstruction coefficient given perfect blocking of direct light by baffles. The corresponding algorithm is based on the ray-tracing formulas in a two-mirror telescope with arbitrary position of the aperture stop. The optimal configuration of baffles is unique. The dependence of the obstruction coefficient upon the telescope characteristics is studied. The optical system can be designed in such a way that the obstruction is equal to a predefined value. As examples, the Hubble Space Telescope and the Ritchey–Chretien system with the obstruction coefficient 0.25 are considered. This revised version was published online in July 2006 with corrections to the Cover Date.     

The university of New South Wales automated patrol telescope

The Automated Patrol Telescope is a wide-field CCD imaging telescope of novel design. The telescope is a converted Baker-Nunn satellite tracking camera that has undergone extensive modification to its optical, mechanical and electronic systems. Telescope operation is entirely under computer control, and the instrument is to be used for a variety of astronomical survey and monitoring projects.     

Development of a Speckle Interferometer and the Measurement of Fried's Parameter (ro) at the Telescope Site

A new optical speckle interferometer for use at the 2.34 meter Vainu Bappu Telescope (VBT), at Vainu Bappu Observatory (VBO), Kavalur, India, has been designed and developed. Provisions have been made for observation both at the prime focus (f/3,25), as well as at the Cassegrain focus (f/13) of the said telescope. The technical details of this sensitive instrument and the design features are described. An interface between the telescope and the afore-mentioned interferometer is made based on a concept of eliminating the formation of eddies due to the hot air entrapment. The performances of this instrument has been tested both at the laboratory, as well as at the Cassegrain end of the telescope. It is being used routinely to observe the speckle-grams of close-binary (separation < 1 arc second) stars. The size of the Fried's parameter, r_o, is also measured.     

Prospects for astrometry with the Hubble Space Telescope

The Hubble Space Telescope (HST), a large optical telescope having an aperture of 2.4 meters and a length of 8.8 meters, is being developed by the National Aeronautics and Space Administration. This telescope will be placed into earth orbit by the space shuttle. Astrometric observations with the HST are made using a Fine Guidance Sensor which is capable of measuring the position of one object relative to another with an accuracy of ±0.002 arcseconds. The astrometric user of HST will be provided with an Astrometric Data Reduction Software package (ADRS). The variety of astrometric problems to be investigated with HST is discussed.     

European Solar Telescope: Progress status

In this paper, the present status of the development of the design of the European Solar Telescope is described. The telescope is devised to have the best possible angular resolution and polarimetric performance, maximizing the throughput of the whole system. To that aim, adaptive optics and multi‐conjugate adaptive optics are integrated in the optical path. The system will have the possibility to correct for the diurnal variation of the distance to the turbulence layers, by using several deformable mirrors, conjugated at different heights. The present optical design of the telescope distributes the optical elements along the optical path in such a way that the instrumental polarization induced by the telescope is minimized and independent of the solar elevation and azimuth. This property represents a large advantage for polarimetric measurements. The ensemble of instruments that are planned is also presented (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Optical photometry using Bradford robotic telescope

The Bradford Robotic Telescope (BRT) is located on Mount Teide at Tenerife and is working, taking observations since 2003. It is a fully automated telescope. The hardware and software used for the working of the telescope are described here. Twenty four BL Lac objects are observed since 2005 and magnitudes of the objects are calculated. We describe in this paper the working of BRT and optical BVR photometry of BL Lac objects, observed during 2005–2007.     

The NST: First results and some lessons for ATST and EST

In January 2009, first light observations with the NST (New Solar Telescope) in Big Bear Solar Observatory (BBSO) were made. NST has a 1.7 m primary with a 1.6 m clear aperture. First observational results in TiO and Hα are shown and discussed. The NST primary mirror is the most aspheric telescope mirror deployed to date. The NST is early in its commissioning, and the plans for this phase will be sketched. Lessons learned in building and implementing the NST are germane for the ATST and EST telescopes and will be discussed. The NST has an off‐axis Gregorian configuration consisting of a parabolic primary, heat‐stop, elliptical secondary and diagonal flats. The focal ratio of the primary mirror is f/2.4. The working wavelength range covers from 0.4 to 1.7 µm in the Coudé Lab beneath the telescope and all wavelengths including the far infrared at the Nasmyth focus on the dome floor (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Hopes and expectations with GREGOR

This contribution to the series of GREGOR inauguration articles addresses the history of the GREGOR telescope. It was obvious since a long time that the study of the atmospheric dynamics on the Sun needs telescopes with a large aperture. So the first plans to replace the 40 years old Gregory‐Coudé Telescope, with its 45 cm primary mirror, by a large, 1.5‐meter telescope date back to 1997. After a positive review of the project by the Deutsche Forschungsgemeinschaft in 2000, the large financial support started in 2000. Unfortunately, the new technology of the Cesic mirrors was not yet ripe to produce the large primary mirror with this light‐weight material. So, the project was much delayed. After recollecting for the reader several dates, I also go through some properties of GREGOR. I recall the aims of the project and discuss difficulties and ways to realise the intentions (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Concept and status of the VLT project

The ESO Very Large Telescope project consists of an array of four 8-m telescopes. This concept presents a very great flexibility and covers a broad range of scientific applications. The most far reaching one is the co-phasing of the four telescopes which will open the way to very high resolution imaging.The funding has been granted in December 1987. The first telescope is scheduled for 1995. The whole array is expected to be completed by the 2000.Paper presented at the Symposium on the JNLT and Related Engineering Developments, Tokyo, November 29–December 2, 1988.     

GREGOR ‐ optical design considerations

After many years of successful work the Gregory Coudé Telescope (GCT) is going to be replaced by GREGOR. This new 1.5 m telescope is the result of design considerations which to a wide extent are based on new technologies. Special aspects of the design are presented, including measures to compensate for optical aberrations caused by instrumental and atmospheric effects (Adaptive Optics). First light is expected for the end of 2004.     

Measuring fiber position errors from spectral data

Precise fiber positioning is crucial to a wide field,multi-fiber spectroscopic survey such as the Guoshoujing Telescope(the Large Sky Area Multi-Object Fiber Spectroscopic Telescope,LAMOST).Nowadays,most position error measurements are based on CCD photographic and image processing techniques.These methods only work for measuring errors orthogonal to the telescope optical axis,but there are also errors that lie parallel to the optical axis of the telescope,such as defocusing,and errors caused by the existing deviation angle between the optical axes of a fiber and the telescope.Directly measuring the two latter types of position errors is difficult for an individual fiber,especially during observations.Possible sources of fiber position errors are discussed in brief for LAMOST.By constructing a model of magnitude loss due to the fiber position error for a point source,we propose an indirect method to calculate both the total and systematic position errors for each individual fiber from spectral data.Restrictions and applications of this method are also discussed.     

Optical instruments for JNLT

The plan for optical instruments for the Japanese National Large Telescope is described. Performance of the first-generation instruments is computed on the basis of tentative designs, and the capability of the telescope is demonstrated.Paper presented at the Symposium on the JNLT and Related Engineering Developments, Tokyo, November 29–December 2, 1988.     

YNST光电导行镜机械设计

YNST(云南1m太阳望远镜)光电导行系统的作用除了获取足够清晰的太阳像用作光电导行外,还参与望远镜光轴的校正.介绍了YNST光电导行镜的光学要求、机械设计结果及镜体设计所采用的被动无热化技术.校核了导行镜在阳光辐照下的热变形,计算了导行镜镜筒的最大弯沉,结果表明,所采用的无热化设计是有效的,导行镜刚度满足导行系统要求...     

EMC design for actuators in the FAST reflector

An active reflector is one of the three main innovations incorporated in the Five-hundredmeter Aperture Spherical radio Telescope(FAST).The deformation of such a huge spherically shaped reflector into different transient parabolic shapes is achieved by using 2225 hydraulic actuators which change the position of the 2225 nodes through the connected down tied cables.For each different tracking process of the telescope,more than 1/3 of these 2225 actuators must be in operation to tune the parabolic aperture accurately and meet the surface error restriction.This means that some of these actuators are inevitably located within the main beam of the receiver,and Electromagnetic Interference(EMI)from the actuators must be mitigated to ensure the scientific output of the telescope.Based on the threshold level of interference detrimental to radio astronomy described in ITU-R Recommendation RA.769 and EMI measurements,the shielding efficiency(SE)requirement for each actuator is set to be 80 d B in the frequency range from 70 MHz to 3 GHz.Therefore,Electromagnetic Compatibility(EMC)was taken into account in the actuator design by measures such as power line filters,optical fibers,shielding enclosures and other structural measures.In 2015,all the actuators had been installed at the FAST site.Till now,no apparent EMI from the actuators has been detected by the receiver,which demonstrates the effectiveness of these EMC measures.     

LAMOST网络控制系统结构

LAMOST(大型多天体分光望远镜)建成后将成为世界上视场最大、光谱观测效率最高的4m级口径以上的光学望远镜。它将要同时高效地观测4000颗星的光谱,这对网络控制系统的设计是巨大的挑战。该文主要从LAMOST网络控制系统构建的角度介绍了系统如何在大数据量、多任务的情况下实现各子系统控制、环境监测、授时和无线远程监控等功能,叙述了在该系统中运用的实时分布式操作系统、实时数据库,全球定位系统(GPS)和全球移动通讯系统(GSM)等多项技术．     

30m环形干涉望远镜

简要介绍了云南天文台对下一代地面大型天文光学望远镜进行的初步研究，依据这些研究结果我们提出研制一个新概念的大型地面望远镜：30m环形干涉望远镜（Ringy Interferometric Telescope），它既有单口径望远镜那样的直接成像能力和分辨率，又可以进行综合孔径模式的高分辨率成像，该计划显著地不同于经典的地面大型望远镜，对其中关键技术的研究正在积极进行之中。