This data service provides the times of rise, set, and transit for the major solar system bodies and selected bright stars. The output table also includes azimuth at rise and set as well as altitude at transit.
Be sure to read the Notes section (on this page beyond the two forms) for definitions and additional details on the data.
Form A - U.S. Cities or Towns
Form B - Locations Worldwide
Notes on the data:
For information on the definitions of terms used, see Rise, Set, and Twilight Definitions.
Altitude (Alt.): the angular distance of a celestial body above or below the horizon, measured along the great circle passing through the body and the zenith. Altitude is 90° minus the zenith distance.
Azimuth (Az.): the angular distance measured eastward along the horizon from a specified reference point (in this data service, north). Azimuth is measured to the point where the great circle determining the altitude of an object meets the horizon.
The altitude and azimuth values are for the center of the apparent disk of the object. The altitude values include the effect of atmospheric refraction when the object is above the horizon. The azimuth values are computed with respect to true north (not magnetic). For instructions on using a true azimuth (bearing) with a compass, see NOAA's Geomagnetism FAQs. To determine the magnetic declination for a specific location and date, see NOAA's Geophysical Data Center - Magnetic Declination calculator.
Horizon: a plane perpendicular to the line from an observer through the zenith.
The user can specify the height of the observer, which can range from the surface of the Earth to a maximum of 10,999 m (the top of the troposphere). It is assumed that the observer's horizon is flat (i.e. no geometric 'dip' is applied) and unobstructed. However, since the light at altitude passes through less atmosphere than it does at sea level, the refraction of the light does vary with height. In most circumstances these changes are small, usually less than a minute in rise/set time. Since the rise/set times are printed only to the nearest minute, most users will not see any differences. However, at high latitudes, the times can vary by several minutes (e.g., see Barrow, Alaska around January 22-25).
This data service incorporates a model that determines the angular refraction by numerically integrating a ray passing through a simple polytropic atmosphere. The model is based on the method described by Hohenkerk and Sinclair  and by Hohenkerk .
For U.S. cities or towns (Form A), the times of the phenomena are presented in the standard time of the place requested, using the current time zone of the place. Standard time in time zones was introduced in the U.S. in 1883, but the time zone boundaries have evolved considerably since then, with places shifting from one zone to another. There is no attempt here to track such changes.
Daylight time is implemented only for U.S. cities or towns (Form A) and only for years 1967 and later, in accordance with the Uniform Time Act of 1966 and subsequent legislation. Daylight time is not used for places currently exempt from it.
Rise and set times are tabulated to a precision of one minute only (i.e. no seconds are tabulated). This is because the observed times of rise and set are affected by random changes in local atmospheric conditions and other local variables which cannot be accurately modeled. Thus, tabulating the times to a higher precision is not practical or normally useful.
Output Table Symbols and Blanks
Blanks may occur in a rise/set table for the Sun, Moon or other objects. This indicates that this particular rise or set event did not occur on the given day. These blanks may occur for a couple of reasons. Blanks occur in the tables in high latitude situations where the object may rise and then be continuously above the horizon for an extended period of time, or conversely finally set after being above the horizon for an extended period of time. Blanks may also occur in a rise/set table as the time of rise/set changes across a day boundary (e.g. Sun sets later and later in the day as summer approaches). Blanks may also occur in the moonrise/moonset table because the time between successive moonrises or moonsets is about 25 hours or about one hour longer than the 24 hour day. Consequently, these gaps in the moonrise/moonset table occur approximately once every 25 days.
The following symbols may appear in the output table:
|*****||There is no event because the object is continually above the horizon.|
|----||There is no event because the object is continually below the horizon.|
|N||Altitude at local transit is measured from the northern horizon.|
|S||Altitude at local transit is measured from the southern horizon.|
|?????||Phenomenon is indeterminate.|
For Sun calculations for high latitudes, one may also see these symbols in the twilight columns:
|/////||There is no event because the Sun is continually above the twilight zenith distance.|
|----||There is no event because the Sun is continually below the twilight zenith distance.|