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List:       kde-commits
Subject:    branches/kstars/code-in/doc/kstars
From:       Akarsh Simha <akarshsimha () gmail ! com>
Date:       2010-12-17 8:51:00
Message-ID: 20101217085100.1AB3AAC8A8 () svn ! kde ! org
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SVN commit 1207243 by asimha:

More patching from Ana. Thanks, Ana!

CCMAIL: constansin5@gmail.com



 M  +24 -30    telescopes.docbook  


--- branches/kstars/code-in/doc/kstars/telescopes.docbook #1207242:1207243
@@ -12,7 +12,7 @@
 <para>
 Invented in Holland at the beginning of the 17th century, telescopes are the tools \
used by astronomers  and astrophysicists for their observations. With the development \
                of modern science, telescopes are
-nowadays used for observing in all ranges of the electromagnetic spectrum, inside \
and outside Earth's +nowadays used for observing in all ranges of the electromagnetic \
spectrum, inside and outside Earth's  atmosphere. Telescopes work by collecting light \
with a large surface aerie called objective that makes  the incoming light to \
converge. The final image will be viewed by using an eyepiece.  </para>
@@ -31,7 +31,7 @@
 describes the light gathering power of a telescope. <quote>Fast</quote> telescopes \
have smaller focal ratios, as they   obtain brighter images in a smaller exposure \
time. As the focal ratio gets bigger, the telescope needs   more exposure time in \
order to obtain a bright image, which is why it is <quote>slower</quote>. The focal \
                ratio is
-usually noted as <quote>f/n</quote>, where n is the ratio of the focal length to the \
aperture. +usually denoted as <quote>f/n</quote>, where n is the ratio of the focal \
length to the aperture.  </para>
 </sect2>
 
@@ -41,13 +41,13 @@
 </indexterm>
 
 <para>
-In order to obtain an image, telescopes use lenses or mirrors. Unfortunately, using \
                both of them results
-in image distortions known as <firstterm>aberrations</firstterm>. Some aberrations \
are common for both  +In order to obtain an image, telescopes use lenses or mirrors. \
Unfortunately, if we use both of them we obtain +image distortions known as \
<firstterm>aberrations</firstterm>. Some aberrations are common for both   lenses and \
mirrors, like <firstterm>astigmatism</firstterm> and <firstterm>curvature of \
field</firstterm>.  
 <firstterm>Astigmatism</firstterm> appears when different parts of the lens or \
mirror make the rays of the incoming   light to converge in slightly different \
                locations on the focal plane. When corrected for astigmatism, \
                <firstterm>curvature 
-of field</firstterm> may appear on the surface of the lens/ mirror, which results in \
the converging of light on a curve +of field</firstterm> may appear on the surface of \
the lens/ mirror, which makes the light to converge on a curve  rather than on a \
plane.  
 Still, there are also lens specific aberrations and mirror specific aberrations.
@@ -58,7 +58,7 @@
 diminished by adding correcting lenses into the system. \
<firstterm>Spherical</firstterm> aberration may also   be a problem for lenses, \
resulting from their shape. Spheroid surfaces will not make the incoming light to \
converge to  a single point, which is why other optical surfaces like paraboloids are \
                preferred. Even by using them
-we aren't still out of trouble, as a coma aberration appears in this case. It \
results from the dependence +we aren't still out of trouble, as coma aberration \
appears in this case. It results from the dependence  of the focal length on the \
angle between the direction of the incoming ray and the optical axis of the  system. \
Thus, images of points that lie off the optical axis are elongated, rather than being \
simple  points, as it would be normal.
@@ -73,9 +73,9 @@
 </indexterm>
 
 <para>
-<firstterm>Magnification</firstterm> is described as the ratio between the focal \
length of the objective and the  +<firstterm>Magnification</firstterm>, the increase \
in angular size of an object as viewed in a telescope, is described as the ratio of \
the focal length of the objective to the   focal length of the eyepiece. So the \
                greater the focal length of the objective, the greater the \
                magnification. If 
-you want to have a large image then you will need a long focal length objective and \
a short focal length eyepiece. +you want to have a large image then you need a long \
focal length objective and a short focal length eyepiece.  
 As an example, if you have a 500 mm objective and a 25 mm eyepiece the resulting \
magnification will be  500 / 25, which is 20, or 20X.
@@ -83,13 +83,13 @@
 </sect2>
 
 <sect2 id="field">
-<title>Field of view</title>
+<title>Field of View</title>
 <indexterm><primary>Telescopes</primary>
 </indexterm>
 
 <para>
-<firstterm>The apparent</firstterm> field of view of a telescope is determined only \
                by the eyepiece. It is a 
-specific characteristic of the eyepiece, usually around 52 degrees. In order to find \
the <firstterm>true field  +The field of view is the angle covered on the sky by the \
telescope.<firstterm>The apparent</firstterm> field of view of a telescope is \
determined only by the eyepiece. It is a  +specific characteristic of it, usually \
around 52 degrees. In order to find the <firstterm>true field   of view</firstterm> \
of a telescope, you need to divide the apparent field of view by the magnification. \
The true   field of view is the actual angle covered on the sky by the telescope.
 </para>
@@ -118,29 +118,23 @@
 
 
 <sect2 id="types">
-<title>Types of telescopes</title>
+<title>Types of Telescopes</title>
 <indexterm><primary>Telescopes</primary>
 </indexterm>
 
 <para>
 As telescopes are used in observations over the entire electromagnetic spectrum, \
                they are classified in
-Optical Telescopes, Ultraviolet, Gamma Ray, X-Ray, Infrared and Radio Telescopes. \
                Each one of them is
-important for a detailed analysis of a celestial object.
+Optical Telescopes, Ultraviolet, Gamma Ray, X-Ray, Infrared and Radio Telescopes. \
Each one of them has its +own, well defined role in obtaining a detailed analysis of \
a celestial object.  </para>
 </sect2>
 
 <sect2 id="optical">
-<title>Optical telescopes</title>
+<title>Optical Telescopes</title>
 <indexterm><primary>Telescopes</primary>
 </indexterm>
 
 <para>
-As telescopes are used in observations over the entire electromagnetic spectrum, \
                they are classified in
-Optical Telescopes, Ultraviolet, Gamma Ray, X-Ray, Infrared and Radio Telescopes. \
                Each one of them is
-important for a detailed analysis of a celestial object.
-</para>
-
-<para>
 Used for observations in the visible field of view, Optical Telescopes are mainly \
Refractors and  Reflectors, the difference between the two of them being the way of \
collecting light from a star.  </para>
@@ -169,7 +163,7 @@
 <para>
 <firstterm>The Newtonian</firstterm> one uses an additional flat mirror placed in \
the vicinity of the prime focus, in the path  of the reflected light. This results in \
                moving the focal point to a different location, on one of the sides \
                of
-the telescope, more accessible for observing. Of course, a mirror place in the path \
of the reflected light +the telescope, more accessible for observing. Of course, a \
mirror placed in the path of the reflected light  will also block part of the \
incoming one, but if the ratio of the surface aeries of the primary mirror to the  \
second one is big enough, the amount of the blocked incoming light is negligible.  \
</para> @@ -177,7 +171,7 @@
 <para>
 <firstterm>The Cassegrain</firstterm> telescope is similar to the Newtonian one but \
this time the secondary mirror reflects  light to the bottom of the telescope. There \
                is a hole at the center of the primary mirror that lets the
-reflected light to go on its way until it converges in the focal point. The \
secondary mirror needs to be +reflected light to go on its way until it converges to \
the focal point. The secondary mirror needs to be  convex, as it is increasing the \
focal length of the optical system. The primary mirror of a Cassegrain  Telescope is \
a paraboloid. By replacing it with a hyperboloid we obtain a Ritchey-Chretien \
telescope. The  advantage of using a <firstterm>Ritchey-Chretien</firstterm> \
telescope is that it removes the coma of the classical reflectors. @@ -187,7 +181,7 \
@@  <firstterm>The Coude</firstterm> type consists of more than one mirror that \
reflects the light to a special room, the Coude  room, which is located below the \
telescope. The advantages of using a Coude telescope are varied, from  obtaining a \
long focal length useful in different fields of astronomy and astrophysics, like \
                spectroscopy
-or just avoid using a massive instrument. But there are also disadvantages to using \
a Coude telescope, as +to avoiding the usage of a massive instrument. But there are \
also disadvantages in using a Coude telescope, because  the more mirrors are placed \
in the system, the less amount of light arrives at the detector. This happens  \
because by using Aluminum mirrors, only 80 % of the incident light gets reflected.  \
</para> @@ -205,7 +199,7 @@
 </sect2>
 
 <sect2 id="other">
-<title>Other wavelengths of telescopes</title>
+<title>Observations in Other Wavelengths</title>
 <indexterm><primary>Telescopes</primary>
 </indexterm>
 
@@ -219,9 +213,9 @@
 is the Arecibo telescope from Puerto Rico that uses a huge dish of 300 m diameter. \
In order to solve  the problem for resolutions, astronomers have developed a new \
technique called interferometry. The  basic principal of interferometry is that by \
                observing the same object with two distinct telescopes we
-can obtain a final image by "connecting" the two initial ones. Nowadays, the most \
efficient observatory +can obtain a final image by "connecting" the two initial ones. \
Nowadays, the most efficient observatory  that uses interferometry is the Very Large \
                Array located near Socorro, New Mexico. It uses 27 telescopes
-placed in a "Y" shape, with 25 m aperture each. There also exists a technique called \
Very Long Baseline +placed in a "Y" shape, with 25 m aperture each. There also exists \
a technique called Very Long Baseline  Interferometry (VLBI) that allows astronomers \
to resolve images over the size of continents. The biggest  project of the century in \
this domain is the building of the Atacama Large Military Array (ALMA), which  will \
be using 50 telescopes placed in the United States, Europe and Japan. @@ -229,12 \
+223,12 @@  </sect2>
 
 <sect2 id="space">
-<title>Other wavelengths of telescopes</title>
+<title>Space-Based Observations</title>
 <indexterm><primary>Telescopes</primary>
 </indexterm>
 
 <para>
-Because Earth-based observations are affected by extinction due Earth's atmosphere, \
observations +Because Earth-based observations are affected by extinction due Earth's \
atmosphere, observations  carried out in space are more successful. We mention the \
<firstterm>Hubble Space Telescope (HST)</firstterm> that has a 2.4,  f/24 primary \
mirror, the smoothest mirror ever constructed. The Hubble Space Telescope is placed \
on a  low-orbit around Earth and because of the lack of atmosphere it can observe \
very faint objects. @@ -243,7 +237,7 @@
 known as the Second Lagrange Point (L2). Here the gravitational attractions due to \
both Sun and Earth  balances the centrifugal force of an object set in motion around \
the Sun. This point has the special  property that if an object is placed here, it is \
                in equilibrium with respect to the Sun-Earth system.
-The second Lagrange Point lies on the line connecting Sun and Earth, on the other \
side of Earth. So a +The second Lagrange Point lies on the line connecting Sun and \
Earth, on the other side of the Earth. So a  telescope placed here will receive less \
thermal radiation, which will improve Infrared Observations.  </para>
 </sect2>


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