The calculator above uses Javascript to generate the local circumstances for the eclipse from any location or city.
Since the calculator uses Javascript, it does not depend on
any CGI script or web server to do its work - all the calculations are done by your computer in your web browser.
The software to do the calculations is hidden within this web page making this an "intelligent" web page!
To use the calculator while not connected to the Internet, choose "File", "Save as..." from your browser's menu, and
save to a location on your hard drive.
Then you can load the saved file into your browser at any time by finding the saved file on your hard drive and double-clicking it!
The 2003 eclipse calculator was developed by Chris O'Byrne.
Please check for
updates to the calculator.
To find the local circumstances of an eclipse, enter your location and time zone information in the Geographic Coordinates section.
Then click on the "Click to calculate eclipse circumstances" button.
The precicted eclipse circumstances will appear in the table below that button.
The times and local circumstances of the eclipse from your location are given in the Predicted Eclipse Circumstances section.
The information given in the first five lines is -
Eclipse event
The local date and time of the event
If the event occurs while the Sun is below the horizon, an asterisk (*) will appear
Alt - The altitude of the Sun, in degrees, above the horizon
Azi - The azimuth of the Sun (0 = due north, 90 = due east, etc.)
P - The angle between the north point on the Sun's disk and the contact point with the Moon
V - The "o'clock" position on the Sun's face of the contact point with the Moon (eg V=12.0 means
that the contact point is in the "12 o'clock" position - ie the top of the Sun's disk).
This differs from the definition of V in the "Annular and Total Solar Eclipses of 2003" (NASA TP 2002-211618) bulletin,
where V is measured counter-clockwise in degrees.
LC - The calculator may be able to determine a correction factor to the time of the start and end of
the annular eclipse due to the fact that the Moon's limb is not smooth. If it is, then the correction
it has applied (in seconds) is given.
The information in the bottom three lines is -
Eclipse type - the type of the eclipse as seen at your location (taking into account that the Sun may
not be above the horizon until the eclipse is in progress, etc.)
Duration - the duration of the annular eclipse. (This box will display "n/a" if the eclipse is
partial only, or "???" if the annular eclipse is underway at sunrise or sunset)
Coverage - the percentage of the Sun's disk covered at mid eclipse. (This box will display "???" if
the Sun is below the horizon at mid eclipse)
Magnitude - the fraction of the Sun's diameter covered by the Moon at mid eclipse
Ratio - the ratio of the apparent size of the Moon to that of the Sun
Antumbral depth - the percentage of the way from the edge of the annular eclipse to the centre
line that this location is at
Limitations
This calculator does not account for atmospheric refraction, which makes a difference if the eclipse occurs close to sunrise or sunset
It is not possible to predict the exact value of Delta T in advance, although the extrapolated value should be good to better that 0.5 seconds.
Acknowledgements
Fred Espenak (aka Mr. Eclipse), who provided the solar
eclipse elements data and the lunar limb correction data upon which this page depends!
Jean Meeus - for his excellent books Elements of Solar Eclipses 1951-2200 and Astronomical
Formulae for Calculators, which provided the algorithms for this page
Stephen McCann - who wrote the eclipse duration code
