Astronomical mirrors

Special coating unit to metallize large astronomic mirrors at the Calar Alto observatory in Spain (BALZERS). 

Many investigations to coat astronomical mirrors have been performed by Strong... 

Sputtered silver mirrors are used for solar energy (qv) collectors and astronomical telescope mirrors. Approximately 3 t/yr of silver are used in the United States for low emissivity windows. 

Micro-Opto-Electro-Mechanical Systems (MOEMS) will be widely integrated in new astronomical instruments for future Extremely Large Telescopes, as well as for existing lOm-class telescopes. The two major applications are programmable slit masks for Multi-Object Spectroscopy (see Ch. 12) and deformable mirrors for Adaptive Optics systems. Eirst prototypes have shown their capabilities. However, big efforts have stiU to be done in order to reach the requirements and to realize reliable devices. 

If this happens, then the components are said to be matched to the beam (see Fig. 2). The requirements of Eq. (30) can be converted into surface quality requirements, concerning chiefly the surface figure and the homogeneity of the reflection factor. In terms familiar to astronomers, the surface figure requirements for gw detectors are in the (A/100, A/200) range on about 1000 cm surfaces (see Fig. 2).This requirement is in practice very difficult to fulfill, and new mirror manufacturing methods had to be developed (see Ch. 19). 

As gamma rays pay no heed to lenses and mirrors, INTEGRAL is a rather special telescope, resembhng rather a nuclear physics installation than an astronomical instrument. As a result, its resolving power will be much lower than that of an optical, UV or X-ray telescope. The identification of gamma sources will thus require support from more conventional forms of astronomy. INTEGRAL is an ESA project. 

AMATEUR ASTRONOMER S HANDBOOK. J.B. Sidgwick. Timeless, comprehensive coverage of telescopes, mirrors, lenses, mountings, telescope drives, micrometers, spectroscopes, more. 189 illustrations. 576pp. 5K 8V. 

Perhaps the most interesting application of a parabola is in the design of mirrors for astronomical telescopes. The rays of light from a star, a galaxy, or even such a nearby celestial object as a planet are essentially parallel. The reflective property of a parabola sends a ray that is parallel to the parabola s axis through the focus. Therefore, if one grinds a mirror with its surface in the shape of a parabola rotated around its axis and if one tilts such a mirror so that its axis points at a star, all the light from that star which strikes the mirror will be concentrated at the mirror s focus. 

The method widely used for silvering the mirrors of astronomical reflecting telescopes and other optical parts is a modification... 

At the same time Hass [29] invented the silicon oxide protected aluminum surface mirror. Protection against mechanical damage became important in mirror fabrication with the exception of Al mirrors for astronomical applications. And finally, for use in the near ultra violet range, pure aluminum films have to be protected primarily against degrading oxidation on exposure to air by covering them with layers of MgF, or LiF, as was found out by Hass et al. [30] in the time between 1955 and 1961. 

A large batch coating system especially designed to coat astronomical telescope mirrors with A1 films is shown in Fig. 37. The mirror substrate to be coated is made of glass ceramics, its thickness is 60 cm and the weight is about 14 tons. 

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