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Horizon
view of Sun and Moon
 top
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The positions of the Sun and Moon are displayed on the
horizon in equirectangular projection.
Altitude and azimuth angles are the
coordinates in the horizontal system of the observer.
Sun and Moon are drawn according to their actual topocentric
diameters (about 0.5 deg.), enlarged by a factor of 20.
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The elongation of the Moon
from the Sun is the angular distance of the two bodies as
viewed from the selected location on the Earth.
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The current value can be found in the Java Console:
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Click the horizon picture to
get displayed the altitude, azimuth and time (for the Sun at
this azimuth angle).
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Twilight
top
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Before sunrise and after sunset the sky is partially
illuminated by scattered sunlight (sun below the horizon,
altitude < 0).
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Twilight:
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dark
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astr.
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naut.
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civil
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day-light
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The times of sunrise, sunset and
twilight (civil, nautical and astronomical) are displayed on
a clock.
Twilight duration at 0 deg latitude (minutes before
rise):
Twilight duration at 30 deg latitude (minutes before
rise):
Twilight duration at 60 deg latitude (minutes before
rise):
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civil
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naut.
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astron.
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Mar 21
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21
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45
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69
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Jun 21
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23
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49
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75
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Sep 23
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21
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45
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69
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Dec 21
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23
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49
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75
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civil
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naut.
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astron.
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Mar 21
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24
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52
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80
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Jun 21
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28
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61
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97
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Sep 23
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24
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52
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80
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Dec 21
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27
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56
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86
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civil
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naut.
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astron.
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Mar 21
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42
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92
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146
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Jun 21
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107
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-
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-
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Sep 23
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42
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92
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146
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Dec 21
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58
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115
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166
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civil twilight:
0 < altitude< - 6 deg.
nautical twilight:
- 6 deg. < alt. < - 12 deg.
astronomical twilight:
- 12 deg. < alt. < - 18 deg.
Details:
"Rise,
Set, and Twilight Definitions" (U.S. Naval
Observatory)
Lighting-Up
Time, Sunrise/Sunset and Twilights (Royal Greenwich
Observatory)
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Sun
Clock
top
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A new window with a large clock can be opened showing the
times of sunrise, sunset and twilight.
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Rise,
Transit and Setting
top
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The times of rise, transit (culmination, greatest
altitude above the horizon) and setting for Sun and Moon are
local times. They should coincide within 1 or 2 minutes with
the values computed by more complex algorithms. The results
are written to the Java Console
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Details:
"Rise,
Set, and Twilight Definitions" (U.S. Naval
Observatory)
Lighting-Up
Time, Sunrise/Sunset and Twilights (Royal Greenwich
Observatory)
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Elevation
(Altitude) and Azimuth of Sun and
Moon
top
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the elevation (altitude) is
the angular distance measured above the horizon,
the azimuth is the angular
distance measured along the horizon,
the direction is given in brackets (Sun Bearing):
0 deg. = N, 90 deg. = E
180 deg. = S, 270 deg. = W
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In nautics, the azimuth is measured eastwards from the
North point, in astronomy westwards from the South point.
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Azimuth
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The azimuth angle at rise and set
(Azo) depends on the
current declination (delta) and on the latitude (beta) of
the observer:
cos (Azo) = sin delta / cos beta
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For summer solstice (delta =
+23.5°) and beta=45° N:
Azo =
56°
and for winter solstice (delta = -23.5°):
Azo =
124°
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Sun and Moon in the
world map
top
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The symbols are the sub-solar and sub-lunar points
(Geographical Position) of Sun
and Moon, where the line from
the Sun or Moon to the centre of the Earth intersects its
surface. The coordinates of the Geographical Position
(latitude and longitude) are the same as the declination
and Greenwich Hour Angle (GHA).
The illuminated part of the moon is displayed as it is
seen from the Sun.
The Tropic of Cancer
(parallel of latitude 23.5° north of the equator) is
the northernmost place in the world where the sun is ever
directly overhead.
The Tropic of Capricorn
(parallel of latitude at 23.5° south of the equator;
marks the farthest point south at which the sun can be seen
directly overhead at noon; south of the parallel the sun
appears less than 90° from the northern horizon at any
day of the year. The sun reaches its vertical position over
the Tropic of Capricorn at about Dec. 22, the summer
solstice for the Southern Hemisphere.
The Arctic Circle at
66.5°N latitude, i.e., 23.5° south of the North
Pole, marks the northernmost point at which the sun can be
seen at the winter solstice (about Dec. 22) and the
southernmost point of the northern polar regions at which
the midnight sun is visible.
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An observer positioned in the Geographical Position
(GP) will see the Sun or Moon
directly in the vertical, above his head.
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Clicking
the map
top
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displays the red shadow of a
50 pixel vertical stick (gnomon) on the horizontal plane at
the location you clicked.
Shadows are cut off if exceeding the right or upper
border of the map.
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and the geographical coordinates
of the clicked location (latitude N/S, longitude
E/W).
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Age
of the Moon, phase,
illumination
top
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The time taken by the Moon on its orbit, from New Moon to
next New Moon, is 29,53 days.
The illuminated fraction is
the ratio of the apparent illuminated area of the disk to
the total area of the disk, as seen from the Earth.
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Age
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Symb.
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Illum.
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0 d
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New
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0 %
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Waxing crescent
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7,38 d
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First quarter
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50 %
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Waxing gibbous
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14.77 d
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Full
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100 %
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Waning gibbous
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22.15 d
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Third quarter
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50%
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Waning crescent
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The phases of the Moon and the illuminated fraction are
(practically) independent of the observer's location on the
Earth.
more details and illustrations
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Terminator,
bright limb of the Moon
top
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the terminator
NBS (an ellipse) is the line
separating the dark and the illuminated part of the Moon.
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The angle of the Moon's bright
limb to the local zenith is listed in the Java
console.
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Prev./Next
New Moon
top
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For the current month, date and time (UT, GMT) of the
previous or next New Moon are computed.
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Distance
of the Moon
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The distance of the Moon from Earth varies between 356410
km (perigee) and 406740 km (apogee).
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user
input /
latitude,
longitude:
top
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Look up your
coordinates:
location
database of DLR (Deutsches Zentrum für Luft- und
Raumfahrt): 2 million towns and villages world-wide or my
database here !
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for a new location:
enter latitude, and press
return key
(not enter key !)
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- degrees latitude as
a non-negative integer or decimal (0° to 90),
and select "N" or "S"
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.
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enter longitude, and press
return key
(not enter key !)
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- degrees longitude as a
non negative integer or decimal (0 to 180),
and select "E" or "W"
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You may also enter a new location by
clicking the word map,
the geographical coordinates of the clicked location
(latitude N/S, longitude E/W) are displayed.
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The coordinates of the user location are stored (during
applet's lifetime) and can be recalled by the location menu
item "User Input".
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home
location
top
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Open "Sme.html" in
Netscape's Composer or in any HTML or text editor. Edit the
parameter values of "location",
"latitude" and
"longitude" parameters
of the applet tag in the upper part of the page.
Enter southern latitude and
western longitudes with a
minus sign !
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<APPLET
CODE="SunMoonEarthxxx.class"
NAME="Sun, Moon & Earth" WIDTH=650 HEIGHT=690
ALIGN=bottom
archive="applet/JavaClasses.jar">
<PARAM name="email" value="replace">
<PARAM name="password"
value="12345">
<PARAM NAME=location VALUE="Berlin">
<PARAM NAME=latitude VALUE="52.51">
<PARAM NAME=longitude VALUE="13.41">
<PARAM NAME=server VALUE=0>
</APPLET>
"xxx" is the version number.
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Look up your
coordinates:
location
database of DLR (Deutsches Zentrum für Luft- und
Raumfahrt): 2 million towns and villages world-wide or my
database here !
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Time
Zone Offset
top
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time difference between local zone time and Greenwich
Time (GMT ),
e.g. +02:00 hours
+ 1 h is the value computed
from the longitude value, without respect to the DST and
which may differ from the actual time zone offset.
The GMT date may be different from the local date:
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Central European Daylight Time = GMT + 2 hours
Central European Time = GMT + 1 hour
"time zone offset is +2 h" (for
Central European Daylight Time)
If necessary, select the correct time zone offset from the
menu.
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Declination
and GHA
top
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The declination and Greenwich Hour Angle (GHA) are the
coordinates (latitude and longitude) of the Geographical
Position (GP) of Sun or Moon,
where the line from the Sun or Moon to the centre of the
Earth intersects its surface.
The local hour angle is:
LHA = GHA +/- longitude
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Equation
of Time
top
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The Equation of
Time is the difference between the time determined by a
sundial and the clock time. It is due to the obliquity of
the Earth's axis and the unequal motion of the Earth
(ellipse). The value, computed for 12:00 UT, is between -14
:20 min (near Feb 12) and +16:24 min (near Nov 4).
The length of the current solar day (i.e. the time interval
between culmination of the Sun on prev. and curent day) is
not exactly 24 hours; the difference is given in brackets
(e.g. +18.8 s).
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For detailed information:
Royal
Greenwich Observatory: 'The Equation of Time'
Sundials
on the Internet:
The Equation of Time
Equation
of Time -- Problem in Astronomy
(M. Müller)
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Data
Window
top
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All data are written to a Data Window (and can be printed
by Copy and Paste)
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See example of data output.
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Date
and Time Menus
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Instead of using the menus for
hour,
date and
month, ...
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you may use the
keys
"h",
"d",
"m" to increase hour,
date, month,
or shift key and
"h",
"d",
"m" to decrease hour,
date, month !
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moon
orbit and celestial equator
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Check the "Moon" box to see the daily orbit of the moon
(green) and the celestial equator (blue).
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visibility of the
moon
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Eclipses
of the Sun and the Moon
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An Eclipse of the sun may occur at New Moon, an eclipse
of the Moon at New Moon,
Check the moon
phases
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Example: 2001 Jan 9
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Example: 2001 June 21
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top
Details for the
orbital phases of the Moon
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Looking to the North Pole
of the Earth:
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1 = New
(conjunction)
2 = Waxing crescent
3 = First
quarter
4 = Waxing gibbous
5 = Full
(opposition)
6 = Waning gibbous
7 = Third
quarter
8 = Waning crescent
1 = New
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New:
Moon transits about the same time as the Sun.
Longitude difference on the map is 0 deg.
Moon in conjunction to Sun: Sun Moon and Earth in a line.
An eclipse of the Sun occurs when declinations are
(nearly) equal.
Solar Eclipses:
1998 Feb 26
1998 Aug 22
1999 Aug 11
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New Moon Phase
(age 1 - 6 days):
rises at dawn, sets at dusk.
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First
quarter:
Moon transits about 6 hours after the Sun.
Longitude difference on the map is 90 deg.
Rectangular position of Moon, Earth and Sun, with right
angle at Earth.
Moon east of Sun,
visible in the evening at west.
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First Quarter Phase
(age 7 - 13 days):
rises at noon, sets at midnight.
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Full:
Longitude difference on the map is 180 deg.
Moon in opposition to Sun, Sun, Earth and Moon in a line.
An eclipse of the Moon occurs when declinations are
(nearly) equal.
Moon is rising when Sun is setting,
at south at midnight.
Lunar Eclipse:
2000 Jan 21
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Full Moon Phase
(age 14 - 21 days):
rises at dusk, sets at dawn.
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Third
quarter:
Moon transits about 6 hours before the Sun.
Longitude difference on the map is 270 deg.
Rectangular position of Moon, Earth and Sun, with right
angle at Earth.
Moon west of Sun.
Moon rising before Sun and then visible at east.
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Last Quarter Moon
(age 22 -27 days):
rises at midnight, sets at noon.
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My
Astronomy Sources
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Meeus, Jean:
Astronomische Algorithmen, Aus d. Engl. v. Dill,
Verlag Barth, J, 2. durchges. Aufl. 1994, 460 S.,
39 Abb. - 24 x 16 cm. - 875. - Gebunden, ISBN
3-335-00400-0
Meeus, Jean:
Astronomical Algorithms
Willmann-Bell; Hardcover (December 1991), ISBN:
0943396352
Meeus, Jean:
Astronomical Formulae for Calculators;
Willmann-Bell; Softcover, ISBN: 0943396220
Montenbruck, Oliver
/ Pfleger, Thomas:
Astronomie mit dem Personal Computer
Springer Bln, 2., überarb. u. stark erw. Aufl.
1994, XI,306 S. 45 Abb., MS DOS Diskette 3,5". -
625. - Gebunden, ISBN 3-540-57701-7
Montenbruck, Oliver
/ Pfleger, Thomas:
Astronomy on the Personal Computer. Inkl. 3
1/2'-Diskette;
Springer Bln, 2nd, corr. and enl. ed. 1994,
XIII,312 pp. 45 figs., 1 MS-DOS Diskette 3,5". -
635. - Hard, ISBN 3-540-57700-9
Montenbruck,
Oliver: Grundlagen der Ephemeridenrechnung, Eine
Zusammenstellung der wichtigsten Formeln und Daten
zur Berechnung der Bahnen von Körpern im
Sonnensystem
Sterne und Weltraum Taschenbücher 00010,
Verlag Sterne u. Weltraum, 5. Aufl. 1992, 172 S.,
41 Abb. - 21 x 15 cm. - 220. - Kartoniert, ISBN
3-87973-913-7
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Web
Links:
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USNO
Master Clock Animated GIF Clocks
U.S. Naval Observatory (Astronomical
Applications Department):
Upcoming
& Recent Eclipses of the Sun and Moon
Frequently
Asked Questions (Rise, Set, and Twilight
Definitions, phases of the Moon, etc.)
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Home
Page: http://www.GeoAstro.de
Juergen
Giesen: jgiesen@t-online.de
GeoAstro
Applet Collection
Last
modified :
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