Obscuration for solar and lunar eclipses

This release provides a new field obscuration in the data structures for lunar eclipses, global solar eclipses, and local solar eclipses. Obscuration is a floating point number that ranges from 0 to 1.

In a solar eclipse, obscuration is the fraction of the Sun's apparent disc area that is blocked from view by the Moon, as seen by the observer on the Earth. In a "global" solar eclipse calculation, the observer's location is given as the ideal location for the maximum eclipse. In a "local" solar eclipse calculation, the caller supplies the desired geographic location for the observer. The value of obscuration is 1 for a total eclipse, and somewhere between 0 and 1 for a partial or annular eclipse.

In a lunar eclipse, obscuration is the fraction of the Moon's apparent disc area that is covered by the Earth's umbra. The value is 1 for a total eclipse, and somewhere between 0 and 1 for a partial eclipse. The obscuration is 0 for penumbral lunar eclipses, because the Earth's umbra does not fall upon the Moon during them. Penumbral eclipses are very difficult to observe because they are faint and subtle, so no separate obscuration metric is reported for them.