Wide Angle Lenses Ebook
The development of array detectors has permitted deep, wide-field surveys at near-infrared wavelengths. These arrays offer two advantages first, larger areal coverage in a single exposure, with a higher spatial resolution than is possible with aperture photometry and second, simultaneous measurement of the sky background, and therefore more accurate sky subtraction. At optical wavelengths, arrays of large-format CCDs provide both wide-angle coverage and 10 times more sensitivity than the photographic plates used for the Palomar and UK Schmidt sky surveys.
Where A is the wavelength of the observations, and 206,265 is the number of arcseconds in a radian. Thus, the human eye, with an effective aperture of 5 mm, has an angular resolution of 20 arcsec an 8-inch (20-cm) telescope can resolve double stars separated by 1 arcsec and the 200-inch (5-metre) Hale telescope at Mount Palomar has a diffraction limit of 0.02 arcsec at visual wavelengths, although atmospheric turbulence (seeing) prevents this resolution being attained in direct observations.
During STS-32, this 'L-cubed' instrument was used by crew members to take repeat photographs of a geographical feature every 15 seconds the data was then fed into an onboard computer, which calculated two possible sets of latitudinal and longitudinal coordinates. The crew, by knowing whether the target was 'north' or 'south' of their flight path, could then determine which set was correct. The instrument, which utilised a modified Hasselblad large-format camera with a wide-angle lens, proved extremely successful.
In all instances, only a single tooth of any one molar type was included for each individual. Thus, unlike the studies by Suwa et al. (1994, 1996), antimeric values were not averaged. As detailed by Smith (1999), cusp area measurements for the living apes were recorded by placing the individual molars in occlusal view below a Canon Hi8 video camera equipped with a 10x macro lens. Each crown was orientated such that the occlusal crown area was maximized. For the fossil specimens, occlusal photographs of either the original specimens or high definition casts were taken following the same method of crown orientation. This method of orientation is likely equivalent to that of Suwa et al. (1994, 1996), in which the area of the occlusal fovea was maximized to define horizontal. It differs somewhat from the methods employed by Wood et al. (1983), who used plane of the cervical line, and Bailey (2004), who used the buccal and distal cervices of upper molars for orientation. Nevertheless, such...
The first case deals with images of Miranda, a satellite of Uranus. Pictures were taken by Voyager 2 on January 24, 1986. Normally one considers the shutter action of a Vidicon camera an instantaneous event, much as the shutter action in a conventional photographic camera. This is not so, however, for several reasons. The problem of taking pictures of Miranda can be compared to the task of taking photographs of a speeding car with a telephoto lens under low light conditions and with a slow film. The light level at Uranus (19.2 Astronomical Units from the Sun) is only 1 368 of that available at the distance of Earth, while the Vidicon sensitivity corresponds to an ASA film rating of two. These factors require an exposure time of 15 s. The spacecraft moved with a speed of 17km s-1 through the Uranian system and the focal length of the narrow angle camera is 1.5 m. Substantial smear would have occurred if the camera pointing had not precisely followed Miranda during the exposure....
Because of the limitation set by seeing, telescopes with very large apertures do not show any greater detail of the Martian surface than do smaller instruments. According to R. S. Richardson, the planet looks as if all the color has been washed out of it when viewed with the full aperture of the 100-inch reflector telescope of the Mount Wilson Observatory, California. The sharpness of the image, he goes on to say, can be considerably improved by diaphragming down, or partially covering, the secondary mirror.
A prominent feature of EUV images is noise. Noise can hide the existing plasmaspheric structures, but it also might create artificial structure. Both effects would compromise the drift analysis. Noise strongly influences the correlation coefficient analysis of image pairs. Figure 16 (left panel) is an example of how noise manifests itself in this analysis for the cross-correlation of the consecutive images shown in Fig. 15. The red arrows indicate the derived plasma flow, where the legend defines the arrow length scaling. The yellow regions mark the overlap between individual EUV imaging sensors. The flow pattern looks much more systematic when a noise mitigation technique is applied first (Fig. 16, right panel). A filter is used here that replaces each pixel by the median value in its surrounding 1 RE x
Figure 9.3 shows the one in South Africa. You can see that it consists of eight telescopes. In fact these are standard cameras, each with an aperture D 200 mm. Such a small aperture puts faint stars beyond the reach of SuperWASP, but the eight cameras between them cover a huge field of view - roughly 2,500 times the area of the Moon in the sky. The SuperWASPs can thus survey much of the sky, and they are doing so, repeatedly. Over the few years it has been operating, brightness variations in many stars have been recorded, but as of October 2007 just three of these have proved to be planets, giant planets, though there are a few promising candidates awaiting confirmation of planetary mass by Doppler spectroscopy. Many more planets are expected to be discovered in the years to come.
Ehrenreich et al. (2006) have further suggested that future large-aperture instruments (such as GMT, TMT, and OWL) may have sufficient sensitivity to detect the ensemble signature of spectroscopic absorption during transit due to moon atmospheres. This may sound extraordinarily unlikely. Only Titan in our Solar System retains a substantial atmosphere. However, this is unlikely to be truly representative. For masses around 0.12-0.23 M at habitable temperatures, a body is likely to not only retain an atmosphere (even within the magnetosphere of a giant planet), but also sustain tectonic activity vital for atmospheric re-cycling and resupply (Sect. 11.3). Furthermore, giant planets appear to exist within zones of stellar irradiation well suited to 'temperate' surface conditions for any moons they harbor (Fig. 11.4). Thus, a wide range of atmospheric types may be possible. It appears likely that in the near future the existence (or absence) of exomoon systems will be established - first...
Taken from the McDonald Observatory, the extensive 1999-2000 optical photometry from Meech et al. (2005), and the narrowband optical photometry of Schleicher et al. for the 1983 and 1994 apparitions. (We note that the scatter in the data from the IDS at McDonald Observatory is much larger than the scatter in the data from the narrowband photometry. It is not clear why this is the case, but we suggest that it is due at least in part to the relatively small effective aperture in IDS, and to the
Crews would often indulge in a little Moon and Earth photography to use up the spare film in their magazines - there was, after all, no point returning it unexposed. However, midway between the Moon and Earth, neither world was particularly photogenic unless very long lenses were used, which they did not possess. Because of this, the Moon tended to be well photographed as they departed, and due to the timing and geometry of the solar system when the flights occurred, it was usually nearing its full phase. Conversely, Earth often appeared as an increasingly thin crescent that, for some flights, led to the spacecraft entering and then exiting Earth's shadow.
The other main type of eye is the compound eye (Figure 15.7). This is the eye found, for example, in insects. Whereas the camera eye has a single lens forming an image on many receptors, the compound eye has many lenses, each one feeding light to a single receptor. Each lens points in a different direction, and so, as with the camera eye, an image is built up from the signals from the receptors. The compound eye needs to be far larger to achieve the same detail as a camera eye provides, because the sensors are spaced further apart - if we had compound eyes they would need to be about a meter across to give us the visual acuity our camera eyes give us. The compound eye does, however, have the advantages of being very sensitive to fast motion in the image, and of having a large field of view. It has evolved independently at least four times.
Although referred to as 'wide angle', the 200-millimetre-focal-length f 3.5 refractor yields a square image that spans only 3.5 x 3.5 degrees, so by any popular measure it is actually a telephoto. The 'narrow angle' camera uses a 2,000-millimetre-focal-length f 10.5 folded-optics reflecting telescope with a field of view that is ten times narrower. The hardware was supplied by JPL, but C.C. Porco of the University of Arizona is the principal investigator for imaging science.
Injections of ketamine and acepromazine, then anesthetized with inhalant isoflurene. Two of the Felis subjects had postorbital processes and short postorbital ligaments, and one had bilaterally complete postorbital bars, as verified by radiographs. Two small incisions (approximately 1-1.5 cm) were made, one in the infraorbital region and one above the center of the orbit. Small markers (consisting of flat-based metal posts) were glued onto the bone with cyanoacrylate adhesive. A high contrast cotton marker was applied to the cornea and sclera. The purpose of the scleral corneal and bone markers was to allow calculation of eye displacement due to masticatory muscle contraction while simultaneously subtracting ancillary head movements. Indwelling bipolar fine-wire EMG electrodes were inserted into the anterior temporalis and medial pterygoid muscles, and connected to a stimulator. These electrodes consisted of two nickel-chromium alloy fine wires (0.05 mm diameter) with the insulation...
The Imaging Science System (ISS) incorporated a 200-millimetre-focal-length f 3 wide-angle lens boresighted with a 1,500-millimetre-focal-length f 8.5 narrow-angle telescope. The field of view of the 'wide' subsystem was actually only 3 degrees across, comparable to using a 500-millimetre 'telephoto' on a 35-millimetre film camera, and the narrow-angle subsystem's field of view was one-tenth the width, so these were both really telescopic subsystems. Each subsystem had its own camera. Unfortunately, CCD solid-state technology was developed just too late to be exploited by Voyager, and a refined version of the vidicon system developed for the later Mariner spacecraft was used. It had an 11 -millimetre-square selenium-sulphur television tube which was 'read out' by a slow-scan process which took 48 seconds to produce an image comprising 800 lines, each with 800 picture elements (pixels), encoding the brightness on a 256-point scale.1 The images were monochrome, but each camera had an...
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