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The Houghton telescope or Lurie–Houghton telescope is a design that uses a wide compound positive-negative lens over the entire front aperture to correct spherical aberration of the main mirror. If desired, the two corrector elements can be made with the same type of glass, since the Houghton corrector's chromatic aberration is minimal.
Adaptive thin shell mirror. [5]Adaptive optics was first envisioned by Horace W. Babcock in 1953, [6] [7] and was also considered in science fiction, as in Poul Anderson's novel Tau Zero (1970), but it did not come into common usage until advances in computer technology during the 1990s made the technique practical.
Comparison of nominal sizes of apertures of the above extremely large telescopes and some notable optical telescopes. An extremely large telescope (ELT) is an astronomical observatory featuring an optical telescope with an aperture for its primary mirror from 20 metres up to 100 metres across, [1] [2] when discussing reflecting telescopes of optical wavelengths including ultraviolet (UV ...
The Arecibo Telescope was a 305 m (1,000 ft) spherical reflector radio telescope built into a natural sinkhole at the Arecibo Observatory located near Arecibo, Puerto Rico.A cable-mount steerable receiver and several radar transmitters for emitting signals were mounted 150 m (492 ft) above the dish.
The 100-inch (2.54 m) Hooker reflecting telescope at Mount Wilson Observatory near Los Angeles, USA, used by Edwin Hubble to measure galaxy redshifts and discover the general expansion of the universe. A telescope is a device used to observe distant objects by their emission, absorption, or reflection of electromagnetic radiation. [1]
The photography term "one f-stop" refers to a factor of √ 2 (approx. 1.41) change in f-number which corresponds to a √ 2 change in aperture diameter, which in turn corresponds to a factor of 2 change in light intensity (by a factor 2 change in the aperture area). Aperture priority is a semi-automatic shooting mode used in cameras.
The f-number N is given by: = where f is the focal length, and D is the diameter of the entrance pupil (effective aperture).It is customary to write f-numbers preceded by "f /", which forms a mathematical expression of the entrance pupil's diameter in terms of f and N. [1]
Since the early '50s, Aperture Science has been working hard on some pretty impressive shower curtain technology, perfecting something called the "Heimlich Counter-Maneuver" (designed to interrupt ...