Details and explanations for "Sun, Moon & Earth Applet"



Horizon view of Sun and Moon

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The positions of the Sun and Moon are displayed on the horizon in equirectangular projection.
Altitude (elevation) 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.

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.

The current value can be found in the Java Console:

Click the horizon picture to get displayed the altitude, azimuth and time (for the Sun at this azimuth angle).

Twilight

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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Before sunrise and after sunset the sky is partially illuminated by scattered sunlight (sun below the horizon, elevation < 0).


Twilight:


dark
astr.
naut.
civil
day-light

 

The times of sunrise, sunset and twilight (civil, nautical and astronomical) are displayed on a clock.

 

 

 

Twilight duration at 50° latitude (minutes before rise):

 

 

 

Twilight duration at 0° latitude (minutes before rise):

 

 

 

Twilight duration at 30° latitude (minutes before rise):

 

 

 

Twilight duration at 60° latitude (minutes before rise):

twilight

 

 

 


civil
naut.
astron.

Mar 21

32
70
110

Jun 21

45
110
-

Sep 23

32
70
110

Dec 21

39
80
120


civil
naut.
astron.

Mar 21

21
45
69

Jun 21

23
49
75

Sep 23

21
45
69

Dec 21

23
49
75


civil
naut.
astron.

Mar 21

24
52
80

Jun 21

28
61
97

Sep 23

24
52
80

Dec 21

27
56
86


civil
naut.
astron.

Mar 21

42
92
146

Jun 21

107
-
-

Sep 23

42
92
146

Dec 21

58
115
166

civil twilight:
0 ° < elevation < - 6 °

nautical twilight:
- 6 ° < elev. < - 12 °

astronomical twilight:
- 12 ° < elev. < - 18 °

Details:

Lighting-Up Time, Sunrise/Sunset and Twilights (Royal Greenwich Observatory)

"Rise, Set, and Twilight Definitions" (U.S. Naval Observatory)

Sun clock

 

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A new window with a large clock can be opened showing the times of sunrise, sunset and twilight.

Rise, Transit and Setting

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The times of rise, transit (meridian passage), 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.
Details transit and culmination

Details:
"Rise, Set, and Twilight Definitions" (U.S. Naval Observatory)
Lighting-Up Time, Sunrise/Sunset and Twilights (Royal Greenwich Observatory)

Altitude (Elevation) and Azimuth of Sun and Moon

 

 

 

 

 

 

 

 

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the altitude (elevation) is the angular distance measured above the horizon,

the azimuth is the angular distance measured along the horizon,
the compass direction is given in brackets (Sun bearing):

0 deg. = N, 90 deg. = E
180 deg. = S, 270 deg. = W

 

azimuth angle

In nautics, the azimuth is measured eastwards from the North point, in astronomy westwards from the South point.

Azimuth

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

For summer solstice (delta = +23.5°) and beta=45° N:

Azo = 56°

and for winter solstice (delta = -23.5°):

Azo = 124°

animation

Sun and Moon on the world map

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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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.

An observer positioned in the Geographical Position (GP) will see the Sun or Moon directly in the vertical, above his head.

Clicking the map

 

 

 

 

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displays the red shadow of a 50 pixel vertical stick (gnomon) on the horizontal plane at the new location.

Shadows are cut off if exceeding the right or upper border of the map.

 

and the geographical coordinates of the clicked location (latitude N/S, longitude E/W).

 

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Age of the Moon, phase, illumination

 

 

 

 

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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.

Age

Symb.


Illumin.

0 d

New

0 %


Waxing crescent


7.38 d

First quarter

50 %


Waxing gibbous


14.77 d

Full

100 %


Waning gibbous


22.15 d

Third quarter

50 %


Waning crescent


The phases of the Moon and the illuminated fraction are (practically) independent of the observer's location on the Earth.

more details and illustrations

Terminator,
bright limb of the Moon

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the terminator NBS (an ellipse) is the line separating the dark and the illuminated part of the Moon.

The angle of the Moon's bright limb to the local zenith is listed in the Java console.

Prev./Next
New Moon

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For the current month, date and time (UT) of the previous or next New Moon are computed.

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Distance of the Moon

The distance of the Moon from Earth varies between 356410 km (perigee) and 406740 km (apogee).

.

user input /
latitude, longitude:

 

 

 

 

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for a new location:
enter latitude, and press return key
(not enter key !)

- degrees latitude as
a non-negative integer or decimal (0 to 90 deg.),
and select "N" or "S"

enter longitude, and press return key
(not enter key !)

- degrees longitude as a
non negative integer or decimal (0 to 180 deg.),
and select "E" or "W"

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.

The coordinates of the user location are stored (during applet's lifetime) and can be recalled by the location menu item "User Input".

home location

 

 

 

 

 

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Open "Sme.html" in Netscape's Composer or in any HTML or text editor. Enter the parameter values of "location", "latitude" and "longitude" parameters:


enter southern latitude and western longitudes with minus sign !

<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>

Look up your coordinates:
location database of  (Heavens-Above): 1 million towns and villages world-wide, or in my database here !

Time Zone Offset

 

 

 

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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:

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.

Declination and GHA

 

 

 

 

 

 

 

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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

Equation of time

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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).

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)

 

Data Window

 

 

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To write the data to the browser's "Java Console" / "Java Messages" window, check the box and press the "now" button or select date and time. The Java window can be opened from the browser's main menu, and then be printed.

Netscape 4.5:
select main menu "Communicator",
item "tools", sub-item "Java Console".

Set options "Web Browser" "Java" before.

Example of data output.

Date and Time Menus

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Instead of using the menus for hour, date and month, ...

You may use the keys "m", "d", "h", "n" to increase the month, date, hour, or minute
or shift key and "m", "d", "h", "n" to decrease he month, date, hour, or minute !

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Moon orbit and celestial equator

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Check the "Moon" box to see the diurnal path of the moon (green),
select "Equator on/off" from the "Details" menu to draw the celestial equator (blue).


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

Example: 2001 Jan 9

Example: 2001 June 21

Parallactic Angle of the Sun
The parallactic angle of the Sun is the angle "at the Sun".
parallectic angle
parallactic
                  angle
The parallactic angle on the prime vertical is equal to 90°-latitude.

 

 

Details for the orbital phases of the Moon

watch animation (by Chris Dolan)

Looking to the North Pole of the Earth:

 

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


New Moon

New Moon:

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



New Moon Phase
(age 1 - 6 days):

rises at dawn, sets at dusk.


First Quarter

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.



First Quarter Phase
(age 7 - 13 days):

rises at noon, sets at midnight.


Full Moon

Full Moon:

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 Eclipses:
1998 Mar 13
1998 Aug 08



Full Moon Phase
(age 14 - 21 days):

rises at dusk, sets at dawn.


Third Quarter

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.



Last Quarter Moon
(age 22 -27 days):

rises at midnight, sets at noon.


USNO Master Clock

Check Your System Clock

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.)

 

 

Last modified: 2012, May 26