An unusual dawn total lunar eclipse presents special challenges and great photo opportunities. Here's what you need to know to make the most of it.
It's fun to watch the Moon fatten up this month knowing that when it's full, we'll have a total lunar eclipse. Be sure to mark the date — Wednesday morning, January 31st.
This will be the year's only eclipse of any kind for U.S. observers, so it's worth the effort to get up early to see it. For observers in the Western Hemisphere, the event happens in the pre-dawn or dawn sky close to the western horizon only an hour or two before sunrise; the farther west you live, the higher the Moon will be in the sky and the more of the eclipse you'll see.
Should clouds threaten, plan a road trip. After last year's total solar eclipse, it doesn't feel weird anymore to drive a hundred miles or more to see a big-time astronomical event. Consult ClearDarkSky and NOAA Satellite Images to make a quick getaway to clear skies. If you're still unable to see it, NASA and Griffith Observatory will offer live feeds.
There's lots of online chatter about this being a Blue Blood Supermoon Eclipse or Super Blue Blood Moon Eclipse or some variation thereof. While all these adjectives are accurate, we don't need them. Every total lunar eclipse is unique and wonderful.
The January 31st full Moon is the second of the month, making it a Blue Moon, at least in the modern sense. The original meaning of the term was the third of four full Moons in a season. By this definition, the next Blue Moon won't occur until May 18, 2019. But take your pick.
The full Moon will also be closer and larger than usual since it reaches perigee (358,994 km) the previous day. This qualifies it for supermoon status. Finally, only the "bloody end" of the Sun's light will remain to illuminate the Moon within Earth's shadow, with the rest scattered away by the atmosphere. Lunar color during an eclipse depends on the clarity of the atmosphere. The less dust, the brighter the Moon's shade. I've seen it as orange as a glowing coal, but during times of strong volcanic activity, the ash-and-volatile-laden air can turn the Moon's hue from blood to mud.
Due to the Moon's low altitude, particularly for those who live in the eastern half of the country, I prepared a series of four maps, one for each time zone, showing its location, general appearance, and altitude at key phases of the eclipse. Altitudes are measured in degrees. A fist held vertically at arm's length spans 10° from top to bottom; index, middle, and ring fingers held together cover 5°, and your little finger masks 1° of sky, or two Moon diameters.
You'll find links to additional diagrams showing the Moon's progress through Earth's shadow with key times and aspects of the eclipse for each time zone at the end of this blog. While the growing light of dawn will compete with the eclipse viewing from the eastern U.S., don't be put off. Your narrow viewing window makes this a very special event for both photography and spiritual-spatial relations.
The Moon's low elevation means we can frame it with familiar landmarks, and the fact that the eclipse occurs at dawn means there will be a good balance of light between the landscape and the Moon. Try to include buildings, an iconic vista, or even morning traffic in the lower half of the frame with the partially or fully eclipsed Moon near the top. The longer the telephoto lens you use, the more dramatic the Moon will appear in comparison to the landscape. Experiment with exposure to get it just right and don't forget that tripod! Refer to this excellent exposure and composition guide by Fred Espenak for tips and details. For more on the eclipse, see Sky & Telescope's earlier story.
We've all read that the full Moon lies directly opposite the Sun from our point of view, but that's only about 95% true. Most full Moons are off a couple of degrees from a perfect lineup. The only time they're (nearly) exactly so is during a total lunar eclipse. From the Central and Mountain time zones, the full Moon will set in total eclipse; at the same time, the Sun rises at your back. For once, we can look ahead to the Moon, then back around at the Sun and find ourselves in the middle right here on Earth. At that moment, it won't be just a diagram anymore.
Sky & Telescope diagrams showing the Moon's progress through the Earth's outer shadow (penumbra) and inner shadow (umbra) are available here: