NOTICE TO USERS
Commander, Naval Meteorology and Oceanography Command is consolidating the command's web presence in accordance with Department of Defense (DoD) and Navy guidance. The U.S. Naval Oceanography portal will be the single access point for all public facing Meteorology and Oceanography products and services. This publicly-accessible portal is currently online at http://www.usno.navy.mil and is being populated. In the near future, non-DoD users will be redirected to this portal.
DoD customers can access all operational data, products and services via the NIPRnet Naval Oceanography Portal site at https://oceanography.navy.mil (CAC required).
Search within our Astronomical Information Center pages:
Terms used on this website
Phenomena of the Sun and Moon
- Rise, Set, and Twilight Definitions
- Lengths of Longest and Shortest Days
- Length of Day and Night at the Equinoxes
- The Dark Days of Winter
- Visibility of the Crescent Moon
- References on Eclipses
- Phases of the Moon and Percent of the Moon Illuminated
Time
- Universal Time and Greenwich Mean Time
- Computing Greenwich Apparent Sidereal Time
- What are the U.S. Time Zones?
- World Time Zone Map
- When Does Daylight Time Begin and End?
Calendars and Historical Events
- Introduction to Calendars
- Leap Years
- U.S. Holidays
- The International Date Line
- The 21st Century and the 3rd Millennium
- The First Sunrise of the New Millennium
Computing Astronomical Data and Phenomena
- Converting Between Julian Dates and Gregorian Calendar Dates
- Computing Times of Rise and Set
- Approximate Solar Coordinates
- Computing Greenwich Apparent Sidereal Time
- Computing Altitude and Azimuth
Other Topics
- Astronomical Data Used for Litigation
- Celestial Navigation Resources
- Astronomy Education Links
- The Seasons and the Earth's Orbit
- Variation in Times of Perihelion and Aphelion
- International Celestial Reference System (ICRS)
- When Did the Asteroids Become Minor Planets?
- Masses of the Largest Asteroids
- "Explaining The Moon Illusion" - why the Moon looks larger close to the horizon (by Lloyd Kaufman and James Kaufman for the Proceedings of the National Academy of Sciences)
- What is a Blue Moon? (by David Harper)
- An Introduction to Green Flashes (by Andrew T. Young, San Diego State University)
- Photographs of an Inferior-Mirage Sunset - strange Sun shapes near the horizon and related phenomena (by Andrew T. Young, San Diego State University)
- Sunspots and Solar Activity
- Weather and Climate
- Sky conditions for astronomical observing
- Tides
- Maps
