Transmitting telescope

The projector chosen for Keck is an afocal Gregorian telescope (see Ch. 3) which expands the beam to a full 50-cm round profile. The final lens is placed with the plane surface facing the sky and the aspheric surface ground to give a 1/10 wave (rms) transmitted wave front. A back reflection from the last surface is used to monitor the quality of the wave front as it leaves the dome. 

The SSI (solid-state imaging) camera on board the Galileo spacecraft transmitted impressive high-resolution pictures of Io s volcanic activity. Active lava lakes, lava curtains , calderas, mountains and plateaus can be seen (McEwen et al., 2000). The Hubble telescope detected both S2 gas and SO2 in a SO2 to S2 ratio of 1 4 in the smoke trail of the volcano Pele. This value suggests an equilibrium between silicate magmas in the neighbourhood of the quartz-fayalite-magnetite buffer (see Sect. 7.2.2). 

Human DNA contains almost twice as much information as is needed to code for all the substances produced in the body. Likewise, the digital data sent from Voyager 2 contain one redundant bit out of every two bits of information. The Hubble space telescope transmits three redundant bits for every bit of information. How is entropy related to the transmission of information What do you think is accomplished by having so many redundant bits of information in both DNA and the space probes ... 

Measurements were done with the HEGRA CT1 telescope during November l-8th 2002. The standalone HEGRA CT1 telescope has a reflector area of 10 m2 and a camera of 127 PMs, each one with 0.25° FOV. Datasets were obtained with the Crab in the central pixel, and OFF source runs were also taken to check for any systematics. For optical observations the central pixel PM was modified. The DC branch, designed to monitor the DC current of the pixel, was adjusted to detect pulses of ms (timescale of the pulse width), and the AC branch, which is designed to transmit the ns fast signals generated by the Cherenkov showers was removed (De Ona-Wilhelmi et al.). 

All sources of error can be divided into systematic and casual. The instrumental polarization (IP) of a telesc ope-polarimeter system is of the first type. It is stipulated, mainly, by that fact that the polarization degree of the light (both reflected and transmitted) varies with incident angle on the optical elements. In astronomical observations such surfaces are the telescopic mirrors, monochromator mirror, diffraction grating, filters, polarizers, SPSP etc. Therefore, even unpolarized light that falls on the main telescope mirror becomes partially elliptically polarized. The contribution of the polarization attributable to the instrument (see [2], for example) is Pj, (pj Qj, Uj and Vj. 

Lenses have been made using glass since microscopes and telescopes were first invented. When visible light is used, this is still generally the case. For transmitted light, the challenge is usually to minimize absorption some telescopes, such as that on Moimt Palomar, use a very wide coated glass reflector. The critical factor is now not transmission but thermal expansion. 

The laser resonator emits an almost parallel beam of light through a partial transmitting output mirror at one end of the resonator. The beam may then be shaped to a different diameter and divergence by a collimator (telescope) optic. Figure 2 illustrates the beam delivery system. 

A nearly parallel Gaussian beam is expanded by a telescope with two lenses of focal lengths / = 1 cm and fi = 10 cm. The spot size at the entrance lens is If = 1 mm. An aperture in the common focal plane of the two lenses acts as a spatial filter to improve the quality of the wavefront in the expanded beam (why ). What is the diameter of this aperture, if 95% of the intensity is transmitted ... 

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