Key to Javascript Lunar Eclipse Explorer
Fred Espenak
Instructions
The Javascript Lunar Eclipse Explorer can compute the local circumstances for every lunar eclipse visible from a city for any century from -1999 to 3000 (2000 BCE to 3000 CE). The followig key describes the data found in the local circunstances tables.
Column Heading Definition/Description
1 Calendar Calendar Date when the eclipse begins.
Date Gregorian Calendar is used for dates after 1582 Oct 15.
Julian Calendar is used for dates before 1582 Oct 04.
2 Ecl. Eclipse Type where:
Type N = Penumbral Eclipse.
P = Partial Eclipse.
T = Total Eclipse.
3 Pen. Penumbral magnitude is the fraction of the Moon's
Mag. DIAMETER obscured by Earth's penumbral shadow.
For penumbral eclipses, it is usually less than 1.0.
4 Umb. Umbral magnitude is the fraction of the Moon's
Mag. DIAMETER obscured by Earth's umbral shadow.
For partial eclipses, it is greater than 0 but less than 1.0.
For total eclipses, it is equal or greater than 1.0.
5 Pen. Local Time when the penumbral eclipse begins.
Eclipse (not visible to the naked eye)
Begins
6 Alt Moon's altitude (in degrees) when penumbral eclipse begins.
7 Partial Local Time when the partial eclipse begins.
Eclipse
Begins
8 Alt Moon's altitude (in degrees) when partial eclipse begins.
9 Total Local Time when the total eclipse begins.
Eclipse
Begins
10 Alt Moon's altitude (in degrees) when total eclipse begins.
11 Mid. Local Time at mid-eclipse.
Eclipse
12 Alt Moon's altitude (in degrees) at mid-eclipse.
13 Total Local Time when the total eclipse ends.
Eclipse
Ends
14 Alt Moon's altitude (in degrees) when total eclipse ends.
15 Partial Local Time when the partial eclipse ends.
Eclipse
Ends
16 Alt Moon's altitude (in degrees) when partial eclipse ends.
17 Pen. Local Time when the penumbral eclipse ends.
Eclipse (not visible to the naked eye)
Ends
18 Alt Moon's altitude (in degrees) when penumbral eclipse ends.
All times are displayed in local time using the value from the Time Zone field in Section 1 (you must add 1 hour if Daylight Saving Time is in effect).
Predicted events shown in gray occur below the horizon and can not be seen from the selected location. The calendar date of an eclipse refers to the start time of the eclipse, even if the Moon is below the horizon at that time. If an eclipse begins before midnight and ends after midnight, the latter phases occur on the following calendar date.
Although the start and end times of penumbral phases are listed in the predictions below, they are only of academic interest. These events are not visible to the eye. For detailed descriptions, see Visual Appearance of Lunar Eclipses. More information is available on the how, what, when, where, and why of lunar eclipses at Lunar Eclipses for Beginners.
The JavaScript Solar Eclipse Explorer is a similar web tool for determining the visibility of solar eclipses from any city.
Acknowledgments
The Javascript Lunar Eclipse Explorer was developed by Chris O'Byrne and Fred Espenak. It features drop-down menus for city coordinates and buttons to select any century from -1999 to 3000 (2000 BCE to 3000 CE). It can be used to explore the frequency and circumstances of all lunar eclipses visible from any location on Earth.
The Besselian elements and values of ΔT used in Javascript Lunar Eclipse Explorer are the same as those used by the Five Millennium Canon of Lunar Eclipses: -1999 to +3000. For the purposes of calculating eclipse circumstances from a given place, the growing uncertainty in the value of ΔT and the corresponding longitude become unacceptably large outside time period of -1999 to 3000 (2000 BCE to 3000 CE).
Permission is freely granted to reproduce this data when accompanied by an acknowledgment:
"Eclipse Predictions by Fred Espenak and Chris O'Byrne (EclipseWise.com)"