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KStars keeps track of thousands of comets and asteroids.
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It uses orbital data published by NASA's Jet Propulsion
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Laboratory (JPL); these data are known as "orbital elements".
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Because these small bodies are easily perturbed as they
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wander about the solar system, their orbital elements must
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be updated regularly. Updating the elements will also add
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any recently-discovered bodies.
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How to update the orbital elements of comets and asteroids:
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-=( 1 )=- The Easy Way.
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Start KStars, then open the "Get New Stuff" Tool by selecting
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"Download Data..." from the File menu, or by pressing Ctrl+D.
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If a new "ephemerides" package is available, select it and press
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the Install button. Voila!
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-=( 2 )=- Doing it Manually.
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It is possible that the ephemerides package is not completely
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up-to-date. Fortunately, it's relatively simple to update the
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files manually whenever you want.
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::NOTE:: If you find that the ephemerides package is woefully
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outdated, and you follow this manual-install procedure, PLEASE
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send your final comets.dat and asteroids.dat files to
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kstars-devel@kde.org! Now is your chance to be a KStars Hero!
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Step 1: The JPL Webpage
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Point your browser to the following URL:
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http://ssd.jpl.nasa.gov/sb_elem.html
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Step 2: The Comets
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Under "ASCII Files", click on the "Comets" link, and save
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this file as ~/.kde/share/apps/kstars/comets.dat (or as
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$TDEDIR/share/apps/kstars/comets.dat for a system-wide install).
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Step 3: The Asteroids
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Under "ASCII Files", click on the "Numbered Asteroids" link,
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and save this file in a working directory as "asteroids.full.dat".
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This file contains about 100,000 asteroids, far more than we
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want to deal with in KStars. I ship KStars with 2000 asteroids;
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you may feel free to keep as many as you want (but be aware that
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larger numbers will require more RAM and will use the CPU more).
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So, how do we pick which of the 100,000 asteroids to keep? I
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think the most sensible option is to sort the list from biggest
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to smallest, and then just keep the 2000 largest (or however
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many you are keeping). However, there isn't a "size" column to
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sort by! Ah, but there *is* an "absolute magnitude" column
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(column 10). Absolute magnitude is a measure of the asteroid's
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intrinsic brightness, which is a good indicator of its size.
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Smaller numbers are brighter, so sorting the file such that the
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magnitudes increase means that the biggest asteroids are at the
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top of the list.
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Use the "sort" command to sort, and the "head" command to cut
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out the first 2000 lines, like this:
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% sort -n -k 10 asteroids.full.dat | head -n 2000 > asteroids.dat
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[[ WARNING: There is (at least) one asteroid with spaces in its
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name ("van de Hulst"), which messes up the columns for that object.
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You may want to rename this object before sorting.]]
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FInally, copy "asteroids.dat" to ~/.kde/share/apps/kstars/ (for
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single-user install) or $TDEDIR/share/apps/kstars/ (for system
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install).
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