2017 August 21 Total Solar Eclipse
Astronomical Applications Dept. Astronomical Applications Dept.
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If, during the progress of a total [solar] eclipse, the gradually diminishing crescent of the sun is watched, nothing remarkable is seen until very near the moment of its total disappearance. But, as the last ray of sunlight vanishes, a scene of unexampled beauty, grandeur, and impressiveness breaks upon the view. The globe of the moon, black as ink, is seen as if it were hanging in mid-air, surrounded by a crown of soft, silvery light, like that which the old painters used to depict around the heads of saints. Besides this "corona", tongues of rose-colored flame of the most fantastic forms shoot out from various points around the edge of the lunar disk. Of these two appearances, the corona was noticed at least as far back as the time of Kepler; indeed, it was not possible for a total eclipse to happen without the spectators seeing it. But it is only within a century that the attention of astronomers has been directed to the rose-colored flames, although an observation of them was recorded in the Philosophical Transactions nearly two centuries ago. They are known by the several names of "flames," "prominences," and "protruberances."
— Simon Newcomb. 1878. Popular Astronomy. New York: Harper & Brothers. p. 252

On 2017 August 21, a total solar eclipse will be visible to fortunate observers in the United States along a narrow band, approximately 73 miles (118 km) wide, that crosses twelve states from Oregon to South Carolina.

Calculate local circumstances

Major U.S. cities in the path of totality: Casper, WY; Kansas City, KS; Jefferson City, MO; Kansas City, MO; Lincoln, NE; Salem, OR; Columbia, SC; Greenville, SC; Nashville, TN, St. Louis, MO; Charleston, SC

Use the forms below to calculate the local circumstances. For cities or towns in the U.S. or its territories, use Form A. For all other locations, use Form B.

Form A - U.S. Cities or Towns

  2017 August 21 (Total)



The place name you enter above must be a city or town in the U.S. The place's location will be retrieved from a file with over 22,000 places listed. Either upper- or lower-case letters or a combination can be used. Spell out place name prefixes, as in "East Orange", "Fort Lauderdale", "Mount Vernon", etc. The only exception is "St.", which is entered as an abbreviation with a period, as in "St. Louis". You need only enter as many characters as will unambiguously identify the place. The city or town name may be left blank if the State or Territory is District of Columbia.

Form B - Locations Worldwide

  2017 August 21 (Total)


The place name you enter above is merely a label for the table header; you can enter any identifier, or none (avoid using punctuation characters). The data will be calculated for the longitude and latitude you enter below.

Note: Coordinate components should be entered as integers (no decimals).


For other eclipses, try our Solar Eclipse Computer. Times are given in UT1; for help converting them to local time, see U.S. Time Zones. Notes on the local eclipse circumstances are located at the bottom of this page.

View US map and circumstances

Her Majesty's Nautical Almanac Office (HMNAO), United Kingdom Hydrographic Office provides a 2017 total solar eclipse map. The map contains detailed information about the eclipse for selected US cities, including local circumstances, animations, and diagrams. Please click on the image to visit the full map.

link to a map of the 2017 Solar Eclipse circumstances in the US

View global map and circumstances (USNO Eclipse Portal)

The USNO Eclipse Portal provides diagrams and animations showing the global circumstances and local circumstances at selected locations. The Portal is a joint effort with Her Majesty's Nautical Almanac Office (HMNAO), United Kingdom Hydrographic Office.

Times are given in UT; for help converting them to local time, see World Time Zone Map.

View global visibility map (The Astronomical Almanac)

Preliminary Eclipse Visibility Map from The Astronomical Almanac (explanation of map).

For visibility maps of other eclipses, see Eclipses of the Sun and Moon.

View circumstances at Shawnee National Forest, Illinois, site of maximum eclipse

Local circumstance diagram for the location of maximum duration of totality (from HMNAO).

General eclipse resources


The table of local circumstances gives the UT1 time of each eclipse "event" that is visible from the location. The altitude and azimuth of the Sun at each of the events is given as well. The azimuth is reckoned eastward from North. The altitude is corrected for refraction assuming standard atmospheric conditions.

The computation of Eclipse Local Circumstances is started by iteratively computing topocentric positions of the Sun and Moon to find the time of Maximum Eclipse. Another series of position computations is performed going backwards and forwards from the time of Maximum Eclipse to find the times of contacts. The solar and lunar angular diameters are calculated at each position using radius values from DE405 (Sun 696000km; Moon 1737.4 km) to determine if contact conditions have occurred. Lunar limb profiles and center of mass/center of figure corrections are not used.

After contact times have been computed, a check is made to determine if Sunrise and/or Sunset occurred during the course of the eclipse. If so, the time of Sunrise and/or Sunset is computed.

The body of the table contains the time of each contact point, the Sun's topocentric position at that time, and its Position and Vertex Angles. The time of sunrise or sunset is also noted in the table if it occurs during the eclipse. The summary at the bottom contains the Duration, Magnitude, and Obscuration.

The Position Angle of a given contact point on the solar limb is measured eastward (counterclockwise) around the solar limb, from the point on the Sun that is farthest north.

Vertex Angle is similar to Position Angle, except that it is measured from the point on the Sun that has the highest local altitude.

Duration is the amount of time from the beginning of the eclipse to the end.

Duration of Totality is the amount of time from the beginning of the central phase eclipse to the end of the central phase. For an annular solar eclipse, it will read Duration of Annularity .

Magnitude of the eclipse is the fraction of the apparent diameter of the solar disk covered by the Moon at the time of greatest phase, expressed in units of solar diameter.

Obscuration is the percentage of the area of the apparent solar disk obscured by the Moon at maximum eclipse.

Additional eclipse definitions

from The Astronomical Almanac Glossary

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.
the angular distance measured eastward along the horizon from a specified reference point (usually north). Azimuth is measured to the point where the great circle determining the altitude of an object meets the horizon.
the difference between Terrestrial Time (TT) and Universal Time (UT): ΔT=TT − UT1.
the obscuration of a celestial body caused by its passage through the shadow cast by another body.
eclipse, solar:
actually an occultation of the Sun by the Moon in which the Earth passes through the shadow cast by the Moon. It may be total (observer in the Moon's umbra), partial (observer in the Moon's penumbra), annular, or annular-total.
the obscuration of one celestial body by another of greater apparent diameter; especially the passage of the Moon in front of a star or planet, or the disappearance of a satellite behind the disk of its primary. If the primary source of illumination of a reflecting body is cut off by the occultation, the phenomenon is also called an eclipse. The occultation of the Sun by the Moon is a solar eclipse.
1. The portion of a shadow in which light from an extended source is partially but not completely cut off by an intervening body. 2. The area of partial shadow surrounding the umbra.
the portion of a shadow cone in which none of the light from an extended light source (ignoring refraction) can be observed.