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Planet Finder Documentation and Source CodeTo use the PlanetFinder applet in your broswer, click here. |
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(1) The program needs to know your location in order to predict
what the sky will look like. Initially, it
just guesses the biggest city in your time zone. If this is
incorrect, you can set your location either by
typing in your latitude and longitude or by choosing a city from
the list (which only includes those with
populations greater than 3 million).
(2) Use 24-hour time for setting the time, e.g. 13:00 means 1
pm.
(3) In the U.S., daylight savings time lasts from 2 am on the
first
sunday of April until 2 am on the last sunday of October. The
program handles this by default. If you are
not in the U.S., you may need to set daylight savings time
manually.
(4) The compass directions may look wrong, but that is because
the screen represents the way
the sky looks when you look straight up. The compass directions
are therefore a mirror image
of the compass directions on a map, which represents a view of
the land looking down from above.
(5) The spherical sky has to be projected onto the flat screen.
This projection produces distortion,
just as a map of the earth inevitably has some distortion. The
greatest distortion occurs near the
horizon.
(6) The disks of the sun, moon, and planets are not drawn to
scale. Their brightnesses are given as magnitudes
to the right of their names. A more negative magnitude means a
brighter planet. The magnitudes given for Saturn
do not include the brightness of the rings, so Saturn will
usually be brighter than indicated.
(7) This program is only designed to have a limited degree of
accuracy, sufficient for most
naked-eye astronomy applications. More detailed information is given
below.
You are welcome either to link to my Planet Finder page or to have the
applet appear in your own page. A possible advantage of the latter is that
in your html code you can set an appropriate language, latitude, and longitude
for the people who visit your page. The following html example shows
how you would include the Danish-language version ("da") in your page,
with the default latitude and longitude set for Copenhagen:
<applet archive="http://www.lightandmatter.com/PlanetFinder.jar"
code="PlanetFinder.class"
width=600 height=400
alt="Sorry, your browser does not support Java.">
<param name="language" value="da">
<param name="latitude" value="56">
<param name="longitude" value="12">
</applet>
Note that, due to a bug, the latitude and longitude as set in the html code must be integers. (The user can type in noninteger values in the applet, and that works fine.)
If you would like to do this, please e-mail me your translation of the following words and phrases. First comes a list of phrases to translate that occur on the web page. After that is some computer code, in which you only need to translate what's inside the quotes. You can just indicate accents in any way that's convenient for you (e.g., "e'" and "o`", or with Unicode), and I'll try to code them correctly for the computer. Of course you should change the references to Italian so they refer to your own language. Thanks!!
Planet Finder [can be translated as something like "Planets Now"
or "Planets Today" -- I leave it up to your judgment to pick whatever sounds
best in your language]
"Light and Matter" web page [You can decide whether quotes are appropriate in your language]
an applet that shows the current locations of the stars and planets in the night sky
Italian version of Planet Finder
Sorry, but I am unable to respond to e-mail in Italian.
Light and Matter home page (in English)
Thanks to (your name) for the Italian translation.
daylightSavings = "Daylight savings";
auto = "Auto";
manual = "Manual";
northLetter = "N";
southLetter = "S";
eastLetter = "E";
westLetter = "W";
sky = "Sky";
innerSolarSystem = "Inner solar system";
outerSolarSystem = "Outer solar system";
update = "Update";
nakedEyePlanetsOnly = "Naked-eye planets only";
timeZone = "Time zone";
monthNames[0] = "Jan"; monthNames[3] = "Apr"; monthNames[6] = "Jul"; monthNames[9] = "Oct";
monthNames[1] = "Feb"; monthNames[4] = "May"; monthNames[7] = "Aug"; monthNames[10] = "Nov";
monthNames[2] = "Mar"; monthNames[5] = "Jun"; monthNames[8] = "Sep"; monthNames[11] = "Dec";
planetNames[0] = "Mercury"; planetNames[3] = "Mars"; planetNames[6] = "Uranus";
planetNames[1] = "Venus"; planetNames[4] = "Jupiter"; planetNames[7] = "Neptune";
planetNames[2] = "Earth"; planetNames[5] = "Saturn"; planetNames[8] = "Pluto";
sun = "Sun";
moon = "Moon";
latitude = "Latitude";
longitude = "Longitude";
localTime = "Local time";
(1) The applet does not quit gracefully, so when you reload the page you get
a bunch of Java errors.
(2) If you program the default latitude and longitude into your html, you
must use integers.
The source code is subject to the GPL open source license. Source code: here.
Kostas Giannakakis has created a C++-language port of PlanetFinder for the Symbian operating system that runs on cell phones.
Planet Finder calculates everything based almost entirely on
Kepler's laws, so it is no good for extremely high-
precision work or for projections many centuries into the past or
future.
The only nonkeplerian behavior incorporated into the program is
the precession of the moon's orbit and the
first few correction terms for the moon's motion given by Paul Schlyter.
The parallax due to the rotation of the earth is taken into
account, but the program does not calculate the
effect of the earth's oblateness or of the time taken for light
to travel from the planets to us. The sun's
motion relative to the solar system's center of mass is taken
into account. Refraction
in the earth's atmosphere is not taken into account, which is
why the times of sunrise and sunset will not agree exactly with
what is listed in the newspaper.
For high-precision calculations,
you may want to check out
Solar System Live, a web page that displays a map of the locations of
the planets in the solar system (not a map of the sky),
or Your Sky, which is a planetarium
applet like this one but fancier and not quite as easy to use.
.
I am very grateful to Paul Schlyter and Dave Williams for their help with the celestial mechanics. Thanks to Kristian Pedersen for the Danish translation.
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(c) Copyright 1998 Benjamin Crowell. All rights reserved. |