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May Night Sky

The first central eclipse of the 21st century sweeps through Albuquerque on May 20

May 2012 Night Sky

Charlie Christmann

Next Chance—October 2023:

Total eclipses don’t happen in any particular spot on Earth very often, but an annular solar eclipse is in the offering for New Mexico on May 20 this year. This is the first central eclipse of the 21st century passing through the continental USA, and the first annular eclipse there since May 1994. Albuquerque just happens to be on the centerline of the maximum eclipse path.

An eclipse of the sun can only happen at the time of any New Moon when the Moon passes between Earth and sun. If the Moon’s shadow happens to fall on the Earth’s surface, we see all or part of the sun’s disk covered. But not every New Moon creates an eclipse. The Moon’s orbit is tipped five degrees relative to the Earth’s orbit causing the shadow to miss Earth most of the time. At least twice a year, things align just right, such that some part of the Moon’s shadow falls on Earth’s surface to create a solar eclipse.

As the Moon orbits the Earth and the Earth spins on its axis, the path of the shadow travels across the ground at approximately 1000 mph.

There are two parts to the Moon’s shadow in a total eclipse: the Penumbra and the Umbra. The Penumbra is where only part of the sun is covered by the Moon and viewers in this area will see a partial eclipse. Under the path of the umbra, the Moon will completely cover the sun. However, this May, we have an annular eclipse. The geometry lines us such that the Moon does not completely cover the sun, leaving a ring of light from the sun around the edges.

So, what is the difference? The apparent size of the Moon depends upon the location of the Moon in its elliptical shaped orbit. During a total eclipse, the Moon is closer to the Earth than during an annular eclipse. On May 19, at 7:50 a.m. MDT, the Moon reaches apogee, its farthest point in its orbit. Thanks to the sun’s pull, this apogee is 252,556 miles away, fourteen Moon diameters farther that its closest perigee point on May 5 (221,800 miles).

New Mexico is near the end of the eclipse path as it sweeps toward us from the west coast. Actually, the sun sets in full annular eclipse near Lubbock, Texas, ending the event. In the town of Bernalillo, maximum eclipse occurs at 7:35:35 p.m. and the Moon will cover the sun for four minutes, seventeen seconds. The eclipse will start at 6:28:56 p.m. when the edge of the Moon first starts to cover the solar disk. At its peak, the Moon will cover 87.1 percent of the sun. The Moon will still be partially covering the sun at sunset.

To view the eclipse, do not use binoculars, a telescope, or your eyes without proper filtering. The sun will blind you! Solar filters are available from astronomy and telescope supply venders, Welder’s goggles, rated at 14 or higher, are safe to use for looking directly at the Sun. They are also relatively inexpensive. You could also build a pinhole projector. See: for instructions. Just remember, regular sunglasses, of any type, will not protect your eyes!

Look at this eclipse, the next total eclipse over central New Mexico won’t happen again until October 14, 2023. But, we will have a chance to see some partial eclipses: August 21, 2017 with just under eighty percent coverage, and on April 8, 2024 with eighty percent coverage.

The Planets and the Moon:

  • Mercury is low in the east about thirty minutes before sunrise the first part of May.
  • After sunset, look for Venus in the WNW, low in the sky, in the constellation Auriga.
  • Mars is high in the SW at sunset in Leo.
  • Saturn is mid-way up in the SSE after sunset in Virgo, and sets just before sunrise.
  • Jupiter is up during daylight hours this month and not readily visible.
  • The Moon is full at 9:34 p.m. on the fifth and new at 5:47 p.m. on the twentieth.
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