Figure 3. A two-element telescope composed of a mirror as the objective and a lens for the eyepiece is shown. This telescope forms an image in the same manner as the two-convex-lens telescope already discussed, but it does not suffer from chromatic aberrations. Such telescopes can gather more light, since larger mirrors than lenses can be constructed. A telescope can also be made with a concave mirror as its first element or objective, since a concave mirror acts like a convex lens as seen in Figure 3.
Flat mirrors are often employed in optical instruments to make them more compact or to send light to cameras and other sensing devices. There are many advantages to using mirrors rather than lenses for telescope objectives. Mirrors can be constructed much larger than lenses and can, thus, gather large amounts of light, as needed to view distant galaxies, for example. Large and relatively flat mirrors have very long focal lengths, so that great angular magnification is possible.
Telescopes, like microscopes, can utilize a range of frequencies from the electromagnetic spectrum. Figure 4a shows the Australia Telescope Compact Array, which uses six m antennas for mapping the southern skies using radio waves.
Figure 4b shows the focusing of x rays on the Chandra X-ray Observatory—a satellite orbiting earth since and looking at high temperature events as exploding stars, quasars, and black holes. X rays, with much more energy and shorter wavelengths than RF and light, are mainly absorbed and not reflected when incident perpendicular to the medium.
But they can be reflected when incident at small glancing angles, much like a rock will skip on a lake if thrown at a small angle. The mirrors for the Chandra consist of a long barrelled pathway and 4 pairs of mirrors to focus the rays at a point 10 meters away from the entrance. The mirrors are extremely smooth and consist of a glass ceramic base with a thin coating of metal iridium. Four pairs of precision manufactured mirrors are exquisitely shaped and aligned so that x rays ricochet off the mirrors like bullets off a wall, focusing on a spot.
Figure 4. X rays ricochet off 4 pairs of mirrors forming a barrelled pathway leading to the focus point. The project will use cutting-edge technologies such as adaptive optics in which the lens or mirror is constructed from lots of carefully aligned tiny lenses and mirrors that can be manipulated using computers.
A range of rapidly changing distortions can be minimized by deforming or tilting the tiny lenses and mirrors. The use of adaptive optics in vision correction is a current area of research. Figure 5. Skip to main content. Vision and Optical Instruments. Can u give diagrams Please. Mike - There are two basic types of telescopes, refracting and reflecting. Refracting telescopes use lenses to focus the light, and reflecting telescopes use mirrors. Refracting telescopes work by using two lenses to focus the light and make it look like the object is closer to you than it really is.
Convex lenses work by bending light inwards like in the diagram. This is what makes the image look smaller. Like the Reflector, uses a concave mirror as its primary objective to focus the incoming light. Usually compound telescopes have a shorter tube than comparable reflectors; yet they are more expensive inch-per-inch than ian reflectors. Radio Telescopes use a metallic usually mesh or solid concave dish to focus the radio waves onto a collector.
Privacy Policy. Skip to main content. Module 5: Telescope and Observing. Search for:. Telescope Optical Types The type of telescope primarily depends on the optical combinations used to collect the incoming light or Electromagnetic Radiation EMR. Binoculars are a type of Refractor; occasionally you will find reflecting binoculars.
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