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Sky Maps: Your Sky, Heavens-above
Longitude and Latitude:
  Martinsville, NJ: LAT: 40° 35' 00 N:  LON 74° 32 37 W - EST=UTC-5, EDT=UTC-4
        Boston, MA: LAT: 42° 21'24" N   LON: 71° 3'24"W
      Homewood, CA: LAT: 39° 5' N       LON: 120° 10' PST=UTC-8, PDT=UTC-7
Clair Tappaan Ldge: LAT: 39° 19' N      LON: 120° 22' PST=UTC-8, PDT=UTC-7
         Davis, CA: Lat: 38° 33' 17" N  Lon: 121° 45' 45" W

Astronomical dawn is the time at which the sun is 18 degrees below the horizon in the morning. Astronomical dawn is that point in time at which the sun starts lightening the sky. Prior to this time, the sky is completely dark.
Astronomers can easily make observations of point sources such as stars, but faint diffuse objects such as nebulae and galaxies can only be properly observed beyond the limit of astronomical dawn.
The time at which Muslims begin their fast during Ramadan.

Nautical dawn is the time at which the sun is 12 degrees below the horizon in the morning. Nautical dawn is defined as that time at which there is just enough sunlight for objects to be distinguishable. Sometimes known as "frist light".

Dawn or civil dawn is the time at which the sun is 6 degrees below the horizon in the morning. Civil dawn is defined as that time at which there is enough light for objects to be distinguishable and that outdoor activities can commence.
The horizon is clearly defined and the brightest stars are visible under good atmospheric conditions in the absence of moonlight or other illumination. The picture to the right was taken at Civil Dawn.

Twilight is the time between the above.
Twilight is the time before the sun rises and after it sets (see below). The length of twilight after sunset and before sunrise is heavily influenced by the latitude of the observer; , while at the equator, it can go from day to night in as little as 20 minutes, at Anchorage Alaska it takes over 40 min..
E.g. Astronomical Twilight is the time between Astronomical dawn and Nautical dawn.
Civil Twilight begins in the morning when the center of the Sun is less than 6° below the horizon, and ends at sunrise.

Dusk is the evening equivalent of dawn.
Nautical dusk is also called "nightfall".

In New York City (Lat: 40° 43')

June 21 EDT
Nautical Dawn: 4:08 (1:17 before sunrise)
Civil Dawn: 4:51 (34 min before sunrise)
Sunrise: 5:25 
Sunset: 20:30 
Civil Dusk: 21:04 (34 min after sunset)
Nautical Dusk: 21:47 (1:17 after sunrise)
Dec. 21: EST
Nautical Dawn: 6:11 (1:05 before sunrise)
Civil Dawn: 6:45 (31 min. before sunrise)
Sunrise: 7:16  
Sunset: 16:31 
Civil Dusk: 17:02 (31 min. after sunset)
Nautical Dusk: 17:37 (1:06 after sunset)
Length of twilight (Time between Civil Dawn and Sunrise) at:
Place Latitude Mar 21 June 21 Sep 21 Dec 21 June 21
Sunrise Sunset Day Length
Honolulu † 21° 18' 22 min 25 min 22 min 24 min 5:50† 19:16 13h 25m
Miami 25° 46' 23 min 26 23 min 25 6:30 20:15 13h 45m
New York 40° 43' 28 min 34 27 min 31 5:25 20:30 15H 5m
Seattle 47° 36' 31 min 40 31 min 36 5:11 21:11 15h 59m
Anchorage 61° 13' 43 min * 43 min 1:02 4:20 23:43 19h 22m
* From June 8th to July 4th at Anchorage (just below the artic circle) there is no nighttime. There is 19 hrs. of daylight and 5 hrs of twilight.
† Hawaii does not observe daylight savings.

Sunrise, Sunset, twilight, dusk and dawn times at: U.S. Naval Observatory (,,

Times above are computed for the Winter Solstice (usually Dec 21 or 22) and Summer Solstice (longest day) June 20 or 21st and Spring Equinox (Mar 20 or 21) and Fall Equinox (Sep. 22 or 23).
The solstice is when the sun is at its greatest distance from the equatorial plane. This is the shortest day of the year (9h 15m in New York) in the winter solstice and longest day (15h 05m in New York) for the summer solstice. Within the polar circles (latitude 66 degrees, 32 minutes)(artic circle and antartic circle), 24-hour daylight is encountered in summer.

The solstice is not the day when the sun rises earliest in the morning nor when it sets latest at night. This varies by location.
For example in New York City the earliest sunrise (5:24) occurs from June 8-20 and latest sunset (20:31) occurs between June 22 and July 2nd.
The latest sunrise (7:20) is from Dec. 31 to Jan. 9th; the earliest sunset (16:28) is from Dec. 3 - 12.

For Miami the earliest sunrise (5:41) occurs between June 11-14.
The latest sunrise (7:00) occurs from Jan. 3-12th.

Location June 21 Dec 21
Azimuth Solar Noon Azimuth Solar Noon
Sunrise sunset time Altitude Sunrise sunset time Altitude
New York 40° 43' 57° 303° 12:57 72.7° 121° 239° 11:54 25.9°
Solar Noon - Sun's position will be right above a location on the same longitude. Newarak NJ is 1 minute after New York City.

Universal Time (UT) Table (UT is the time in the Greenwich time zone which used to be called Grenwich Mean Time)
UT 0 3 6 9 12 15 18 21

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last updated 9 Dec 2006