Commit ea0a312b authored by Lauri Watts's avatar Lauri Watts
Browse files

Cleanup

svn path=/trunk/kdeedu/doc/kstars/; revision=186644
parent 359a735a
......@@ -31,7 +31,7 @@ are not committed until you press the <guibutton>Ok</guibutton> button.
</para><para>
In the <guilabel>Catalogs</guilabel> tab, you determine which object catalogs
are displayed in the map. The SAO star catalog also allows you to set the
"faint limit" for stars, and the magnitude (brightness) limit for displaying
<quote>faint limit</quote> for stars, and the magnitude (brightness) limit for displaying
the names and/or magnitudes of stars. Below the stars section, there is a box
containing a list of checkboxes for the available deep-sky object catalogs.
You can add your own custom object catalogs by pressing the <guibutton>Add
......@@ -47,7 +47,7 @@ or images, and whether name labels should be attached to the Planets.
The <guilabel>Guides</guilabel> tab lets you toggle whether non-objects are
displayed (&ie;, constellation lines, constellation names, Milky Way contour,
celestial equator, ecliptic, horizon line, and opaque ground). You can also
choose whether you would like to see Latin constellation names, IAU-standard
choose whether you would like to see Latin constellation names, <acronym>IAU</acronym>-standard
three-letter abbreviations, or names using your local language.
</para><para>
The <guilabel>Colors</guilabel> tab allows you to set the color scheme, and to
......
<sect1 id="ai-cpoles">
<sect1info>
<author>
<firstname>Jason</firstname>
<surname>Harris</surname>
</author>
</sect1info>
<title>The Celestial Poles</title>
<para>
The sky appears to drift overhead from east to west, completing a full circuit
around the sky in 24 (<link linkend="ai-sidereal">Sidereal</link>) hours. This
phenomenon is due to the spinning of the Earth on its axis. The Earth's
spin axis intersects the <link linkend="ai-csphere">Celestial Sphere</link> at
two points. These points are the <firstterm>Celestial Poles</firstterm>. As the
Earth spins; they remain fixed in the sky, and all other points seem to rotate
around them. The celestial poles are also the poles of the <link
linkend="equatorial">Equatorial Coordinate System</link>, meaning
they have <firstterm>Declinations</firstterm> of +90 degrees and -90 degrees
(for the North and South celestial poles, respectively).
</para><para>
The North Celestial Pole currently has nearly the same coordinates as
the bright star <firstterm>Polaris</firstterm> (which is Latin for <quote>Pole Star</quote>).
This makes Polaris useful for navigation: not only is it always above the North
point of the horizon, but its <link
linkend="horizontal">Altitude</link> angle is always (nearly)
equal to the observer's <link linkend="ai-geocoords">Geographic Latitude</link>
(however, Polaris can only be seen from locations in the Northern hemisphere).
</para><para>
The fact that Polaris is near the pole is purely a coincidence. In fact,
because of <link linkend="ai-precession">Precession</link>, Polaris is only near
the pole for a small fraction of the time.
</para>
<tip>
<para>Exercises:</para>
<para>
Use the <guilabel>Find Object</guilabel> window
(<keycombo action="simul">&Ctrl;<keycap>F</keycap></keycombo>) to locate
Polaris. Notice that its Declination is almost (but not exactly) +90 degrees.
Compare the Altitude reading when focused on Polaris to your location's
geographic latitude. They are always within one degree of each other.
They are not exactly the same because Polaris isn't exactly at the Pole.
(you can point exactly at the pole by switching to Equatorial
coordinates, and pressing the up-arrow key until the sky stops scrolling).
</para><para>
Use the <guilabel>Time Step</guilabel> spinbox in the toolbar to accelerate time
to a
step of 100 seconds. You can see the entire sky appears to rotate around
Polaris, while Polaris itself remains nearly stationary.
</para><para>
We said that the celestial pole is the pole of the Equatorial coordinate
system. What do you think is the pole of the horizontal (Altitude/Azimuth)
coordinate system? (The <link linkend="ai-zenith">Zenith</link>).
</para>
</tip>
</sect1>
......@@ -72,15 +72,16 @@ Calculator</quote> by Peter Duffet-Smith</para></listitem>
Meeus</para></listitem>
</itemizedlist>
</para>
<para>
Special thanks: To the &kde; and &Qt; developers for providing the
world with a peerless set of free API libraries. To the KDevelop
team, for their excellent IDE, which made developing &kstars; so much
easier and more fun. To everyone on the KDevelop message board, the
KDE mailing lists, and on irc.kde.org, for answering my frequent
questions. Thank you to Anne-Marie Mahfouf, for inviting KStars to
join the KDE-Edu module. Finally, thanks to everyone who has submitted
bug reports and other feedback. Thank you, everyone.
<para> Special thanks: To the &kde; and &Qt; developers for providing
the world with a peerless set of free <acronym>API</acronym>
libraries. To the <application>KDevelop</application> team, for their excellent
<acronym>IDE</acronym>, which made developing &kstars; so much easier
and more fun. To everyone on the <application>KDevelop</application> message board, the &kde;
mailing lists, and on irc.kde.org, for answering my frequent
questions. Thank you to Anne-Marie Mahfouf, for inviting &kstars; to
join the &kde;-Edu module. Finally, thanks to everyone who has
submitted bug reports and other feedback. Thank you, everyone.
</para>
<para>
......
......@@ -17,28 +17,25 @@ Scientists are now quite comfortable with the idea that 90% of the
mass is the universe is in a form of matter that cannot be seen.
</para>
<para>
Despite comprehensive maps of the nearby universe that cover the
spectrum from radio to gamma rays, we are only able to account of 10%
of the mass that must be out there. As Bruce H. Margon, an astronomer
at the University of Washington, told the New York Times in 2001:
"It's a fairly embarrassing situation to admit that we can't find 90
percent of the universe".
</para>
<para> Despite comprehensive maps of the nearby universe that cover
the spectrum from radio to gamma rays, we are only able to account of
10% of the mass that must be out there. As Bruce H. Margon, an
astronomer at the University of Washington, told the New York Times in
2001: <citation>It's a fairly embarrassing situation to admit that we
can't find 90 percent of the universe</citation>. </para>
<para>
The term given this "missing mass" is <firstterm>Dark
Matter</firstterm>, and those two words pretty well sum up everything
we know about it at this point. We know there is "Matter", because we
can see the effects of its gravitational influence. However, the
matter emits no detectable electromagnetic radiation at all, hence it
is "Dark". There exist several theories to account for the missing
mass ranging from exotic subatomic particles, to a population of
isolated black holes, to less exotic brown and white dwarfs. The
term 'missing mass' might be misleading, since the mass itself is not
<para> The term given this <quote>missing mass</quote> is
<firstterm>Dark Matter</firstterm>, and those two words pretty well
sum up everything we know about it at this point. We know there is
<quote>Matter</quote>, because we can see the effects of its
gravitational influence. However, the matter emits no detectable
electromagnetic radiation at all, hence it is <quote>Dark</quote>.
There exist several theories to account for the missing mass ranging
from exotic subatomic particles, to a population of isolated black
holes, to less exotic brown and white dwarfs. The term <quote>missing
mass</quote> might be misleading, since the mass itself is not
missing, just its light. But what is exactly dark matter and how do
we really know it exists, if we can't see it?
</para>
we really know it exists, if we can't see it? </para>
<para>
The story began in 1933 when Astronomer Fritz Zwicky was studying the
......@@ -98,26 +95,24 @@ to be spinning apart, there must be mass in the galaxy that we are not
accounting for when we add up all the parts we can see.
</para>
<para>
Several theories have surfaced in literature to account for the
missing mass such as WIMPs (Weakly Interacting Massive Particles),
MACHOs (MAssive Compact Halo Objects), primordial black holes, massive
neutrinos, and others; each with their pros and cons. No single
theory has yet been accepted by the astronomical community, because
we so far lack the means to conclusively test one theory against the
other.
</para>
<para> Several theories have surfaced in literature to account for the
missing mass such as <acronym>WIMP</acronym>s (Weakly Interacting
Massive Particles), <acronym>MACHO</acronym>s (MAssive Compact Halo
Objects), primordial black holes, massive neutrinos, and others; each
with their pros and cons. No single theory has yet been accepted by
the astronomical community, because we so far lack the means to
conclusively test one theory against the other. </para>
<tip>
<para>
You can see the galaxy clusters that Professor Zwicky studied to
discover Dark Matter. Use the KStars Find Object Window
(<keycombo><keycap>Ctrl</keycap><keycap>f</keycap></keycombo>) to
center on "M 87" to find the Virgo Cluster, and on "NGC 4884" to find
the Coma Cluster. You may have to zoom in to see the galaxies.
Note that the Virgo Cluster appears to be much larger on the
sky. In reality, Coma is the larger cluster; it only appears smaller
because it is further away.
discover Dark Matter. Use the &kstars; Find Object Window
(<keycombo action="simul">&Ctrl;<keycap>F</keycap></keycombo>) to
center on <quote>M 87</quote> to find the Virgo Cluster, and on
<quote>NGC 4884</quote> to find the Coma Cluster. You may have to
zoom in to see the galaxies. Note that the Virgo Cluster appears to
be much larger on the sky. In reality, Coma is the larger cluster;
it only appears smaller because it is further away.
</para>
</tip>
</sect1>
<sect1 id="ai-ecliptic">
<sect1info>
<author>
<firstname>John</firstname>
<surname>Cirillo</surname>
</author>
</sect1info>
<title>The Ecliptic</title>
<para>
The ecliptic is an imaginary <link linkend="ai-greatcircle">Great Circle</link>
on the <link linkend="ai-csphere">Celestial Sphere</link> along which the Sun
appears to move over the course of a year. Of course, it is really the
Earth's orbit around the Sun causing the change in the Sun's apparent
direction. The ecliptic is inclined from the <firstterm>Celestial
Equator</firstterm> by 23.5 degrees. The two points where the ecliptic crosses
the celestial equator are known as the <link
linkend="ai-equinox">Equinoxes</link>.
</para><para>
Since our solar system is relatively flat, the orbits of the planets are
also close to the plane of the ecliptic. In addition, the constellations of the
zodiac are located along the ecliptic. This makes the ecliptic a very useful
line of reference to anyone attempting to locate the planets or the
constellations of the zodiac, since they all literally <quote>follow the
Sun</quote>.
</para><para>
The <firstterm>Altitude</firstterm> of the ecliptic above the Horizon changes
over the course of the year, because of the 23.5 degree tilt of the Earth's spin
axis. This causes the seasons. When the ecliptic (and therefore the Sun) is
high above the horizon, the days are longer, and you have Summer. When the
ecliptic is low in the sky, you have Winter.
</para>
<tip>
<para>Exercises:</para>
<para>
Open the <guilabel>View Options</guilabel> window, and switch to Horizontal
coordinates, with the Opaque Ground shown. Open the <guilabel>Set
Time</guilabel> window
(<keycombo action="simul">&Ctrl;<keycap>S</keycap></keycombo>),and change the
Date to sometime in the middle of Summer, and the Time to 12:00 Noon. Back in
the Main Window, point toward the Southern Horizon (press <keycap>S</keycap>).
Note the height of the Sun above the Horizon at Noon in the Summer. Now, change
the Date to something in the middle of Winter (but keep the Time at 12:00 Noon).
The Sun is now much lower in the Sky.
</para>
</tip>
</sect1>
......@@ -11,21 +11,19 @@
<title>Elliptical Galaxies</title>
<para>
Elliptical galaxies are spheroidal concentrations of stars that
resemble Globular Clusters on a
grand scale. They have very little internal structure; the density of
stars declines smoothly from the concentrated center to the diffuse
edge, and they can have a broad range of ellipticities (or aspect
ratios). They typically contain very little interstellar gas and
dust, and no young stellar populations (although there are exceptions
to these rules). Edwin Hubble referred to Elliptical galaxies as
"early-type" galaxies, because he thought that they evolved to become
Spiral Galaxies (which he called "late-type" galaxies). Astronomers
actually now believe the opposite is the case (i.e., that Spiral
galaxies can turn into Elliptical galaxies), but Hubble's early- and
late-type labels are still used.
</para>
<para> Elliptical galaxies are spheroidal concentrations of stars that
resemble Globular Clusters on a grand scale. They have very little
internal structure; the density of stars declines smoothly from the
concentrated center to the diffuse edge, and they can have a broad
range of ellipticities (or aspect ratios). They typically contain
very little interstellar gas and dust, and no young stellar
populations (although there are exceptions to these rules). Edwin
Hubble referred to Elliptical galaxies as <quote>early-type</quote>
galaxies, because he thought that they evolved to become Spiral
Galaxies (which he called <quote>late-type</quote> galaxies).
Astronomers actually now believe the opposite is the case (&ie;, that
Spiral galaxies can turn into Elliptical galaxies), but Hubble's
early- and late-type labels are still used. </para>
<para>
Once thought to be a simple galaxy type, ellipticals are now known to
......@@ -45,57 +43,72 @@ dwarf Ellipticals just a bit brighter than the average globular
cluster. They are divided to several morphological classes:
</para>
<itemizedlist>
<listitem><para>cD Galaxies: Immense and bright objects that can
<variablelist>
<varlistentry>
<term>cD galaxies:</term>
<listitem><para>
Immense and bright objects that can
measure nearly 1 Megaparsec (3 million light years) across. These
titans are only found near the centers of large, dense clusters of
galaxies, and are likely the result of many galaxy
mergers.</para></listitem>
</varlistentry>
<listitem><para>Normal Elliptical galaxies: Condensed Object with
<varlistentry>
<term>Normal Elliptical galaxies</term>
<listitem><para>Condensed Object with
relatively high central surface brightness. They include the giant
ellipticals (gE'e), intermediate-luminosity ellipticals (E's), and
compact ellipticals.</para></listitem>
</varlistentry>
<listitem><para>Dwarf elliptical galaxies (dE's): This class of
<varlistentry>
<term>Dwarf elliptical galaxies (dE's)</term>
<listitem><para> This class of
galaxies is fundamentally different from normal ellipticals. Their
diameters on the order of 1 to 10 kiloparsec with surface brightness
that is much lower than normal ellipticals, giving them a much more
diffuse appearance. They display the same characteristic gradual
decline of star density from a relatively dense core out to a diffuse
periphery.</para></listitem>
</varlistentry>
<listitem><para>
Dwarf spheroidal galaxies (dSph's): Extreme low-luminosity, low
<varlistentry>
<term>Dwarf spheroidal galaxies (dSph's)</term>
<listitem><para>Extreme low-luminosity, low
surface-brightness and have only been observed in the vicinity of the
Milky Way, and possibly other very nearby galaxy groups, such as the
Leo group. Their absolute magnitudes are only -8 to -15 mag.
The Draco dwarf spheroidal galaxy has an absolute magnitude of -8.6,
making it fainter than the average globular cluster in the Milky Way!
</para></listitem>
</varlistentry>
<listitem><para>
Blue compact dwarf galaxies (BCD's): Small galaxies that are unusually
<varlistentry>
<term>Blue compact dwarf galaxies (BCD's)</term>
<listitem>
<para> Small galaxies that are unusually
blue. Thehave photometric colors of B-V = 0.0 to 0.30 mag, which is
typical for relatively young stars of <firstterm>spectral type</firstterm> A.
This suggests that BCDs
are currently actively forming stars. These systems also have
abundant interstellar gas (unlike other Elliptical galaxies).
</para></listitem>
</itemizedlist>
</varlistentry>
</variablelist>
<tip>
<para>
You can see examples of Elliptical galaxies in KStars, using the Find
You can see examples of Elliptical galaxies in &kstars;, using the Find
Object window
(<keycombo><keycap>Ctrl</keycap><keycap>f</keycap></keycombo>).
(<keycombo action="simul">&Ctrl;<keycap>F</keycap></keycombo>).
Search for NGC 4881, which is the Giant cD galaxy in the Coma
cluster of galaxies. M 86 is a normal Elliptical galaxy in the Virgo
cluster of galaxies. M 32 is a dwarf Elliptical that is a satellite
of our neighbor, the Andromeda galaxy (M 31). M 110 is another
satellite of M 31 that is a borderline dwarf spheroidal galaxy
("borderline" because it is somewhat brighter than most other dwarf
spheroidals).
(<quote>borderline</quote> because it is somewhat brighter than most other
dwarf spheroidals).
</para>
</tip>
</sect1>
......@@ -3,7 +3,6 @@
"dtd/kdex.dtd" [
<!ENTITY kappname "&kstars;">
<!ENTITY package "kdeedu">
<!ENTITY astroinfo SYSTEM "astroinfo.docbook">
<!ENTITY blackbody SYSTEM "blackbody.docbook">
<!ENTITY colorandtemp SYSTEM "colorandtemp.docbook">
......@@ -111,8 +110,8 @@
<legalnotice>&FDLNotice;</legalnotice>
<date>2002-09-10</date>
<releaseinfo>0.09.01</releaseinfo>
<date>2002-10-08</date>
<releaseinfo>0.9.1</releaseinfo>
<abstract>
<para>
......@@ -158,7 +157,8 @@ the automated bug reporting tool, accessible from the Help menu.
</para>
</chapter>
&quicktour; <!--A Quick Tour of KStars-->
&quicktour;
<!--A Quick Tour of KStars-->
&config; <!--Configuring KStars-->
&commands; <!--Command Reference-->
&astroinfo; <!--AstroInfo Articles-->
......
<sect1 id="ai-leapyear">
<sect1info>
<author>
<firstname>Jason</firstname>
<surname>Harris</surname>
</author>
</sect1info>
<title>Leap Years</title>
<para>
The Earth has two major components of motion. First, it spins on its rotational
axis; a full spin rotation takes one <firstterm>Day</firstterm> to complete.
Second, it orbits around the Sun; a full orbital rotation takes one
<firstterm>Year</firstterm> to complete.
</para><para>
There are normally 365 days in one <emphasis>calendar</emphasis> year, but it
turns out that a <emphasis>true</emphasis> year (&ie;, a full orbit of the Earth
around the Sun; also called a <firstterm>tropical year</firstterm>) is a little
bit longer than 365 days. In other words, in the time it takes the Earth to
complete one orbital circuit, it completes 365.24219 spin rotations. Don't be
too suprised by this; there's no reason to expect the spin and orbital motions
of the Earth to be synchronized in any way. However, it does make marking
calendar time a bit awkward!
</para><para>
What would happen if we simply ignored the extra 0.24219 rotation at the end of
the year, and simply defined a calendar year to always be 365.0 days long? The
calendar is basically a charting of the Earth's progress around the Sun. If we
ignore the extra bit at the end of each year, then with every passing year, the
calendar date lags a little more behind the true position of Earth around the
Sun. In a few centuries, Winter will begin in September!
</para><para>
In fact, it used to be that all years <emphasis>were</emphasis> defined to have
365.0 days, and the calendar <quote>drifted</quote> away from the true seasons
as a result. In the year 46 <abbrev>BCE</abbrev>, Julius Caeser established the
<firstterm>Julian Calendar</firstterm>, which implemented the world's first
<firstterm>leap years</firstterm>: He decreed that every 4th year would be 366
days long, so that a year was 365.25 days long, on average. This basically
solved the calendar drift problem.
</para><para>
However, the problem wasn't completely solved by the Julian calendar, because a
tropical year isn't 365.25 days long; it's 365.24219 days long! You still have
a calendar drift problem, it just takes many centuries to become
noticeable. And so, in 1582, Pope Gregory XIII instituted the
<firstterm>Gregorian calendar</firstterm>, which was largely the same as the
Julian Calendar, with one more trick added for leap years: even Century years
(those ending with the digits <quote>00</quote>) are only leap years if they are divisible by
400. So, the years 1700, 1800, and 1900 were not leap years (though they would
have been under the Julian Calendar), whereas the year 2000
<emphasis>was</emphasis> a leap year. This change makes the average length of a
year 365.2425 days. So, there is still a tiny calendar drift, but it amounts to
an error of only 3 days in 10,000 years! The Gregorian calendar is still used as
a standard calendar throughout most of the world.
</para>
<note>
<para>
Fun Trivia: When Pope Gregory instituted the Gregorian Calendar, the Julian
Calendar had been followed for over 1500 years, and so the calendar date had
already drifted by over a week. Pope Gregory re-synchronized the calendar by
simply <emphasis>eliminating</emphasis> 10 days! In 1582, the day after October
4th was October 15th!
</para>
</note>
</sect1>
......@@ -9,14 +9,17 @@
</para><para>
2500 years ago, the ancient Greek astronomer Hipparchus classified the
brightnesses of visible stars in the sky on a scale from 1 to 6. He
called the very brightest stars in the sky "first magnitude", and the
very faintest stars he could see "sixth magnitude". Amazingly, two
called the very brightest stars in the sky <quote>first magnitude</quote>, and the
very faintest stars he could see <quote>sixth magnitude</quote>. Amazingly, two
and a half millenia later, Hipparchus's classification scheme is still
widely used by astronomers, although it has since been modernized and
quantified. (Note that the magnitude scale runs backwards to what you
quantified.</para>
<note><para>The magnitude scale runs backwards to what you
might expect: brighter stars have <emphasis>smaller</emphasis>
magnitudes than fainter stars).
</para><para>
</para>
</note>
<para>
The modern magnitude scale is a quantitative measurement of the
<firstterm>flux</firstterm> of light coming from a star, with a
logarithmic scaling:
......@@ -67,8 +70,8 @@ can image stars nearly as faint as 30th magnitude, which is one
</para><para>
A final note: the magnitude is usually measured through a color filter
of some kind, and these magnitudes are denoted by a subscript
describing the filter (i.e., m_V is the magnitude through a "visual"
describing the filter (&ie;, m_V is the magnitude through a <quote>visual</quote>
filter, which is greenish; m_B is the magnitude through a blue filter;
m_pg is the photographic plate magnitude, etc.).
m_pg is the photographic plate magnitude, &etc;).
</para>
</sect1>
......@@ -19,7 +19,7 @@
Because the Earth is in orbit around the Sun, we observe the sky from
a constantly moving position in space. Therefore, we should expect
to see an <firstterm>annual parallax</firstterm> effect, in which the
positions of nearby objects appear to "wobble" back and forth in
positions of nearby objects appear to <quote>wobble</quote> back and forth in
response to our motion around the Sun. This does in fact happen, but
the distances to even the nearest stars are so great that you need to
make careful observations with a telescope to detect
......@@ -53,8 +53,8 @@ larger
arcsecond". One parsec is the distance a star would have if its
observed parallax angle was one arcsecond. It is equal to 3.26
light-years, or 31 trillion kilometers<footnote><para>Astronomers
like this unit so much that they now use "kiloparsecs" to measure
galaxy-scale distances, and "Megaparsecs" to measure intergalactic
like this unit so much that they now use <quote>kiloparsecs</quote> to measure
galaxy-scale distances, and <quote>Megaparsecs</quote> to measure intergalactic
distances, even though these distances are much too large to have an
actual, observable parallax. Other methods are required to determine
these distances</para></footnote>.
......
<sect1 id="ai-precession">
<sect1info>
<author>
<firstname>Jason</firstname>
<surname>Harris</surname>
</author>
</sect1info>
<title>Precession</title>
<para>
<firstterm>Precession</firstterm> is the gradual change in the direction of the
Earth's spin axis. The spin axis traces a cone, completing a full circuit in
26,000 years. If you've ever spun a top or a dreidel, the
<quote>wobbling</quote> rotation of the top as it spins is precession.
</para><para>
Because the direction of the Earth's spin axis changes, so does the location of
the <link linkend="ai-cpoles">Celestial Poles</link>.
</para><para>
The reason for the Earth's precession is complicated. The Earth is not a
perfect sphere, it is a bit flattened, meaning the
<link linkend="ai-greatcircle">Great Circle</link> of the equator is longer
than a <quote>meridonal</quote> great circle that
passes through the poles. Also, the Moon and Sun lie outside the Earth's
Equatorial plane. As a result, the gravitational pull of the Moon and Sun on
the oblate Earth induces a slight <emphasis>torque</emphasis> in addition to a
linear force. This torque on the spinning body of the Earth leads to the
precessional motion.
</para>
<tip>
<para>Exercise:</para>
<para>
Precession is easiest to see by observing the <link
linkend="ai-cpoles">Celestial Pole</link>. To find the pole, first switch to
Equatorial Coordinates in the <guilabel>View Options</guilabel> window, and
then hold down the <keycap>Up arrow</keycap> key until the display stops scrolling. The
declination displayed in the center of the <guilabel>Info Panel</guilabel>
should be +90 degrees, and the bright star Polaris should be nearly at the
center of the screen. Try slewing with the left and right arrow keys. Notice
that the sky appears to rotate around the Pole.
</para><para>
We will now demonstrate Precession by changing the Date to a very remote year,
and observing that the location of the Celestial Pole is no longer near Polaris.
Open the <guilabel>Set Time</guilabel> window
(<keycombo action="simul">&Ctrl;<keycap>S</keycap></keycombo>), and set the date
to the year 8000 (currently, &kstars; cannot handle dates much more remote than
this, but this date is sufficient for our purposes). Notice that the sky
display is now centered at a point between the constellations Cygnus and
Cepheus. Veryify that this is actually the pole by slewing left and right: the
sky rotates about this point; in the year 8000, the North celestial pole will no
longer be near Polaris!
</para>
</tip>
</sect1>
......@@ -3,7 +3,7 @@
<para>
This chapter introduces most of the useful features of &kstars;, in the
form of a guided tour.
form of a guided tour.</para>
<screenshot>
<screeninfo>
......@@ -18,27 +18,25 @@ Here's a screenshot of the &kstars; main window:
</textobject>
</mediaobject>
</screenshot>
</para>
<para>
In the above screenshot, you can see the sky display centered
<para> In the above screenshot, you can see the sky display centered
on the constellation Orion, which is about to set below the western
horizon. Stars are displayed with realistic colors and relative
brightnesses. The brightest stars have their names labeled (&eg;,
Betelgeuse). M 42, the Orion Nebula, is visible below Orion's "belt"
stars, just above the horizon. In three corners of the Sky display,
there are on-screen text labels displaying data on the current time
("LT: 11:38:34 09/10/02"), the current Geographic Location
("Greenwich, United Kingdom"), and the current object in the center of
the display ("Focused on: nothing"). Above the sky display, there are
two toolbars. The main toolbar contains shortcuts for menu functions,
as well as a time-step widget which controls how fast the simulation
clock runs. The view toolbar contains buttons that toggle the display
of different kinds of objects in the sky. At the bottom of the
window, there is a status bar which displays the name of any object
you click on, and the sky coordinates (Right Ascension and
Declination) of the mouse cursor.
</para>
Betelgeuse). M 42, the Orion Nebula, is visible below Orion's
<quote>belt</quote> stars, just above the horizon. In three corners
of the Sky display, there are on-screen text labels displaying data on
the current time (<quote>LT: 11:38:34 09/10/02</quote>), the current
Geographic Location (<quote>Greenwich, United Kingdom</quote>),
and the current object in the center of the display
(<quote>Focused on: nothing</quote>). Above the sky display,
there are two toolbars. The main toolbar contains shortcuts for menu
functions, as well as a time-step widget which controls how fast the
simulation clock runs. The view toolbar contains buttons that toggle
the display of different kinds of objects in the sky. At the bottom
of the window, there is a status bar which displays the name of any
object you click on, and the sky coordinates (Right Ascension and
Declination) of the mouse cursor. </para>
<sect1 id="geolocation">
<title>Where am I?</title>
......@@ -73,13 +71,14 @@ window:
</para>
<para>
In the upper right, there is a list of over 2000 predefined cities.
There is a list of over 2000 predefined cities available to choose from.
You set your location by highlighting a city from this list. Each
city is represented in the world map as a small dot, and when a city
is highlighted in the list, a red crosshairs appears on its location
in the map.
</para><para>
It isn't practical to scroll through the full list of 2000 locations,
</para>
<para>It isn't practical to scroll through the full list of 2000 locations,
looking for a specific city. To make searches easier, the list can be
filtered by entering text in the boxes below the map. For example, in
the screenshot, the text <quote>Ba</quote> appears in the
......@@ -142,11 +141,13 @@ pressing the <guiicon>hourglass</guiicon> icon in the toolbar. The
widget, coupled with three spinboxes for setting the hours, minutes and
seconds. If you ever need to reset the clock back to the current time,
just select <guimenuitem>Set Time to Now</guimenuitem> from the
<guimenu>Time</guimenu> menu. [NB: the current version of KStars cannot
<guimenu>Time</guimenu> menu.</para>
<note><para>The current version of &kstars; cannot
accept dates before October 1, 1752, nor dates after the year 8000.
These are limitations of the Qt Date/Time class. We may implement our
own date/time class in a future version.]
</para>
These are limitations of the &Qt; Date/Time class. We may implement our
own date/time class in a future version.</para></note>
</sect1>
<sect1 id="lookaround">
......@@ -157,18 +158,25 @@ You can pan the display using the arrow keys. If you hold down the
&Shift; key before panning, the scrolling speed is doubled. The
display can also be panned by clicking and dragging with the mouse. Note
that while the display is scrolling, not all objects are displayed. This
is done to cut down on the CPU load of recomputing object positions, which