By Michael-Leonard Creditor
For those of you around SoCal, and especially here in San Diego, who got excited last summer about the “Great American Eclipse” of the sun, your next eclipse is coming up this very month on January 31.
What? Another eclipse? Didn’t hear anything about it? Relax, it’s not your fault. Media doesn’t make nearly the same noise for an upcoming lunar eclipse (they are much more common) as for a major event like the one last summer. A Total Lunar Eclipse (TLE) isn’t nearly as spectacular as a Total Solar Eclipse. But TLEs, as they are known, have a special beauty of their own.
They are totally unlike each other. First of all, one happens during the day, the other is only visible at night. That means the whole underlying feeling of the event is as different as… (do I need to say it?). Also, the area of Earth where the eclipse can be seen is much larger.
And most importantly, in a lunar eclipse totality can last an hour or more, not mere minutes. From first contact until the absolute end both eclipses take about 5 hours for the entire thing to happen, but that passage of time seems much more intense in a solar eclipse. In a lunar eclipse, time seems to slow to a crawl.
Solar eclipses can only be viewed in totality along a relatively narrow track, prosaically called the Path of Totality. Under the most favorable circumstances, totality can last for no longer than 7½ minutes in any one place; last summer’s eclipse featured not quite 2½ minutes of totality. The region where a partial eclipse can be observed is much larger, but truly, the partial phases are no great thing. So, a Total Solar Eclipse could be called a couple of hours of slowly gathering dusk, culminating in a few frantic minutes of the spectacular darkness of totality, followed by the anti-climax of a couple hours of growing lightness.
In a lunar eclipse, however, the umbral phase, the equivalent of totality itself, can last from about 30 minutes to well over an hour. The difference is decided by the position of the moon as it passes through the earth’s shadow. Since her orbit varies from that of Earth and sun, the path Diana takes through the shadow is different each time. If the path is at or near the centerline of the shadow, the phase lasts longer than if Diana describes a shorter route through the shadow. So, no two lunar eclipses are alike.
Since this astronomical event is called an eclipse, not just an occultation, it means that something is being hidden from sight. In a solar eclipse, obviously that’s Sol, the sun; in a lunar eclipse, it’s Diana, the moon. So if the moon is hidden, what can we see?
Ah, that’s another neat thing about lunar eclipses: unlike a Total Solar Eclipse, where Sol is completely hidden behind the moon (allowing us to see the corona and all those wonderful flares), parts of Diana can still be seen as she passes into Earth’s shadow. This is because the light rays from the sun are bent by Earth’s atmosphere partially illuminating portions of the moon that aren’t within the central part of the umbra. Parts of the moon can be totally obscured, but it’s the fascinating red color that really draws TLE viewers back again.
As the moon passes through the Earth’s shadow, the quality of the light being reflected from her surface (and to our eyes) also changes. And, unlike the sudden shift into the totality of a solar eclipse, the changes in a lunar eclipse are much more gradual. The only way a viewer would know that the event had entered the umbral phase – the equivalent of totality – is to consult a timepiece. Relaxed, like I wrote up top.
The color of the moon going through earth’s shadow is not even. Because of the amount of light spilling around the Earth’s shadow, portions of the Moon can be very bright, especially in contrast to the much redder areas. The exact brightness distribution in the umbra is difficult to predict, adding to the differences of every eclipse.
For us here on the west coast, this eclipse will begin at about 3 a.m. But, like I keep sayin’, relax; you don’t need to get up yet. You can sleep in another hour or so until the penumbral phase, when the effects of moving into the shadow begin to be visible, and this won’t even begin until almost 4 a.m.
The umbral phase, when there’s the greatest color, begins an hour later and lasts about 1¼ hours with Diana deepest in the shadow at 5:30 a.m. Again, because the changes are so gradual, exact times don’t really matter here, but if you begin viewing at about 5 a.m. you will have missed nothing.
The eclipse ends either with moonset or with Diana ducking down into the coastal clouds. If we are fortunate enough to have a clear sky to the west, the color of the eclipse adds to the redness produced by our atmosphere to produce a striking vision as the still-very-red orb drops into the Pacific.
Where to view any lunar eclipse can be as simple as going out into your yard. But, one of the really great things about lunar eclipses is they take long enough that you can move to different locations during the event. For example, you could drive to Balboa Park and see the moon at greatest eclipse hovering over the California Tower in Balboa Park and still have enough time to get down to the coast for moonset.
All of this depends on the weather being clear. Especially over the ocean. Especially in the early morning. Remember the old San Diego weather saying: Night and morning low clouds and fog. That’s why I have a saying, too, about any kind of astronomical observation or photography: Astronomy giveth and meteorology taketh away. On the other hand, it is middle of winter so chances of clear sky are better than other times of year.
Five a.m. in the middle of winter… So yes, you do have to get up early if you want to catch this sky show. But you can be relaxed. And if you ask me, the chance is worth it.
By the way, this is a lunar eclipse happening on a blue moon — the second full moon of a calendar month. Last time this occurred on Earth was pretty recently, too: December 31, 2009. But it wasn’t visible here.
|Eclipse event phase||UTC time||San Diego time|
|Penumbral Eclipse Begins||10:51||2:51|
|Partial Eclipse Begin||11:48||3:48|
|Umbral (Total) Eclipse Begins||12:52||4:52|
Moon’s elevation at maximum eclipse: 15.6º, azimuth: 280º
|Umbral (Total) Eclipse Ends||14:08||6:08|
|Partial Eclipse Ends||15:11:11||moonset 6:49 azimuth: 290º
(sunrise at 6:44)
2018 eclipse website page: here
Photographer’s ephemeris: here
About the author
- Born in Tucson AZ; reared in Brooklyn NY; lived in Portland OR; currently resides in Clairemont.
- Three main professions: photographer, folklorist, radio program host.
- Philosopher, mensch, and life-long Liberal.