Types of Lunar Eclipses
An eclipse of the Moon (or lunar eclipse) can only occur at Full Moon, and only if the Moon passes through some portion of Earth’s shadow. That shadow is actually composed of two cone-shaped components, one nested inside the other. The outer or penumbral shadow is a zone where the Earth blocks part but not all of the Sun’s rays from reaching the Moon.In contrast, the inner or umbral shadow is a region where the Earth blocks all direct sunlight from reaching the Moon.
Astronomers recognize three basic types of lunar eclipses:
1. Penumbral Lunar Eclipse
- The Moon passes through Earth’s penumbral shadow.
- These events are of only academic interest because they are subtle and hard to observe.
2. Partial Lunar Eclipse
- A portion of the Moon passes through Earth’s umbral shadow.
- These events are easy to see, even with the unaided eye.
3. Total Lunar Eclipse
- The entire Moon passes through Earth’s umbral shadow.
- These events are quite striking due to the Moon’s vibrant red color during the total phase (totality).
The first eclipse of the year is well placed for observers throughout the Western Hemisphere. The eclipse occurs at the lunar orbit’s ascending node in Virgo. The apparent diameter of the Moon is close to its average since the eclipse occurs nearly midway between apogee (April 08 at 14:53 UT) and perigee (April 23 at 00:28 UT). This is the first of four consecutive total lunar eclipses in 2014 and 2015.
Moon’s orbital trajectory takes it through the southern half of Earth’s umbral shadow. Although the eclipse is not central, the total phase still lasts 78 minutes. The times of the major eclipse phases are listed below:
Penumbral Eclipse Begins: 04:53:37 UT = 10:53:37 CDT (4/14) Partial Eclipse Begins: 05:58:19 UT = 11:58:19 CDT (4/14) Total Eclipse Begins: 07:06:47 UT = 01:06:47 CDT Greatest Eclipse: 07:45:40 UT = 01:45:40 CDT Total Eclipse Ends: 08:24:35 UT = 02:24:35 CDT Partial Eclipse Ends: 09:33:04 UT = 03:33:04 CDT Penumbral Eclipse Ends: 10:37:37 UT = 04:37:37 CDT
At the instant of greatest eclipse (07:45:40 UT) the Moon lies at the zenith for a point in the South Pacific about 3000 km southwest of the Galapagos Islands. The umbral eclipse magnitude peaks at 1.2907 as the Moon’s northern limb passes 1.7 arc-minutes south of the shadow’s central axis. In contrast, the Moon’s southern limb lies 9.0 arc-minutes from the southern edge of the umbra and 40.0 arc-minutes from the shadow centre. Thus, the northern half of the Moon will appear much darker than the southern half because it lies deeper in the umbra. Since the Moon samples a large range of umbral depths during totality, its appearance will change significantly with time. It is not possible to predict the exact brightness distribution in the umbra, so observers are encouraged to estimate the Danjon value at different times during totality. Note that it may also be necessary to assign different Danjon values to different portions of the Moon (i.e., north verses south).
During totality, the spring constellations are well placed for viewing so a number of bright stars can be used for magnitude comparisons. Spica (m = +1.05) is the most conspicuous star lying just 2° west of the eclipsed Moon. This juxtaposition reminds the author of the total lunar eclipse of 1968 Apr 13 when Spica appeared only 1.3° southwest of the Moon at mid-totality. The brilliant blue color of Spica made for a striking contrast with the crimson Moon. Just a week past opposition, Mars (m = -1.4) appears two magnitudes brighter than Spica and lies 9.5° northwest of the Moon. Arcturus (m = +0.15) is 32° to the north, Saturn (m = +0.2) is 26° to the east, and Antares (m = +1.07) is 44° to the southeast.
The entire event is visible from both North and South America. Observers in the western Pacific miss the first half of the eclipse because it occurs before moonrise. Likewise most of Europe and Africa experience moonset just as the eclipse begins. None of the eclipse is visible from north/east Europe, eastern Africa, the Middle East or Central Asia.
The April 15 eclipse is the 56th eclipse of Saros 122. This series began on 1022 August 14 and is composed of 74 lunar eclipses in the following sequence: 22 penumbral, 8 partial, 28 total, 7 partial, and 9 penumbral eclipses (Espenak and Meeus, 2009). The last eclipse of the series is on 2338 October 29.