To determine whether any stage of a lunar eclipse is visible from a specific geographic location, it is simply a matter of calculating the Moon's altitude during each phase of the eclipse. The calculations can be performed on any pocket calculator having trigonometric functions (SIN, COS, TAN). Armed with the latitude and longitude of the location, you also need the celestial coordinates of the Moon and the Greenwich Siderial Time at 00:00 UT. These data are all available via the Five Millennium Catalog of Lunar Eclipses. For the equations and an example of how to calculate the Moon's altitude for a specific location, see Altitude of the Moon.
For convenience, four Microsoft Excel 97 spreadsheet files have been prepared which perform the above calculations automatically. They cover the present period from 1951 through 2050 and are arranged into four convenient date intervals:
To use a table, you simply enter the desired location name, latitude and longitude. The table then calculates the altitude of the Moon at that location for every contact and for every lunar eclipse during that period.
Please note that these files will not open properly unless you have Excel 97 (or newer) installed on your computer. If you do not have Excel, you can download a free Excel Viewer (for Windows PC's) from Microsoft. When each of the eclipse files is downloaded, it will be opened automatically by Excel where you will be able to enter the coordinates of any geographic location to calculate the lunar eclipse visibility. The spreadsheets are protected so that you can not accidently delete or edit any information required by the calculations. Only the name and coordinates of the geographic location (in the green box of each spreadsheet) may be modified.
Each Excel table includes all lunar eclipses over a 25 year period and contains the following data. The calendar date of the instant of greatest eclipse[1] and the lunar eclipse type (T=Total, P=Partial, or N=Penumbral) are found in the first two columns. The penumbral and umbral magnitudes of the eclipse are defined at greatest eclipse as the fractions of the Moon's diameter obscured by penumbral and umbral shadows, respectively. Each contact time of the Moon with Earth's penumbral and umbral shadows are listed (in Universal Time [2] ). The Moon's Geocentric Right Ascension and Declination at greatest eclipse and the Greenwich Sidereal Time at 00:00 U.T. are also given. For a more detailed description of these fields, see lunar eclipse visibility key.
The final seven columns display the calculated altitude of the Moon at each phase of every eclipse for the currently selected geographic position. If the Moon is above the horizon (i.e. - visible), then the cell is pale yellow in color. Otherwise, the cell is gray to indicate that the Moon cannot be seen at that time. These cells are dynamic. Their values and colors change as the observer's geographic coordinates (green cells) are modified.
The lunar coordinates (RA & Dec) used in these tables are geocentric coordinates for the instant of greatest eclipse. Due to its orbital motion, the Moon's position may differ by up to 1.5 degrees at the start or end of the eclipse. Furthermore, horizontal parallax can shift the Moon's apparent position up to about 1 degree around moonrise and moonset. Consequently, the Moon's actual altitude at any location may differ by up to 2.5 degrees from the tables due to these factors. Such precision is adequate for most applications especially since the approximations greatly simplify the visibility calculations.
[1] Greatest eclipse is defined as the instant when the Moon passes closest to the axis of Earth's shadows. This marks the instant when the Moon is deepest in Earth's shadow(s).
[2] For most practical purposes, Universal Time (UT) is equivalent to Greenwich Mean Time (GMT).
All eclipse calculations are by Fred Espenak, and he assumes full responsibility for their accuracy. Some of the information presented in these tables is based on data originally published in Fifty Year Canon of Lunar Eclipses: 1986 - 2035.
Special thanks to eclipse chaser Michael Gill for enthusiastically and rigorously beta-testing this page and for catching typographic errors. (2004 Feb)
Permission is freely granted to reproduce this data when accompanied by an acknowledgment.
