Horizon view of Sun and Moon go back top			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                                                     go back top	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):	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   go back top		A new window with a large clock can be opened showing the times of sunrise, sunset and twilight.
Rise, Transit and Setting go back top		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                 go back top		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	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                             go back top		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         go back top		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).	..
Age of the Moon, phase, illumination         go back top	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 go back top		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 go back top		For the current month, date and time (UT) of the previous or next New Moon are computed.	.
Distance of the Moon		The distance of the Moon from Earth varies between 356410 km (perigee) and 406740 km (apogee).	.
user input / latitude, longitude:         go back top		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           go back top	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       go back top		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               go back top		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 go back top		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     go back top		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 go back top	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 !	.
Moon orbit and celestial equator go back top		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     go back top	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".		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: 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: 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: 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: 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