Capture the subtle lunar eclipse on Monday morning

Howling at the moon on Sunday night? From Sunday night to Monday morning of November 30th not only the penultimate full moon for 2020, but the last lunar eclipse of the year, with a penumbral eclipse of the moon.

The eclipse is a subtle penumbral eclipse, the fourth and final of four such eclipses in 2020 and the last lunar eclipse of the decade. The Moon will not turn blood red like it does during a total lunar eclipse – at most, expect a subtle tea-colored tinge to cover the Moon, with perhaps an uneven discoloration on the northwestern edge of the Moon near the middle of the eclipse.

The eclipse is visible in its entirety from North America, while South America sees the ongoing eclipse at sunrise / moonset, and East Asia and Australia see the ongoing eclipse at sunset / moonrise. moon. Hawaii has the best view, with the Moon eclipsed very close to zenith.

The times for the eclipse are:

• The Moon begins entering the penumbral shadow of the Earth (P1) at 7:32 universal time (UT) / 2:32 Eastern standard time (EST) on Monday November 30th.
• Half of the eclipse occurs at 9:44 UT / 4:44 AM EST.
• The Moon exits the penumbral shadow of the Earth (P4) at 11:53 UT / 6:53 AM EST.

The entire eclipse lasts 4 hours and 21 minutes … but the best time to take a look and see perhaps a slight shadow on the Moon is around the middle of the eclipse, when the Moon is 83% in penumbra of the Earth. The juuuust moon misses the inner dark shadow of the Earth’s shadow by less than 10 arc minutes.

This eclipse also marks the start of the final eclipse season for 2020. If the Moon’s orbit were aligned with the Earth’s ecliptic flight around the Sun, we would see an eclipse every 29.5-day synodic period: a ‘ lunar and solar eclipses during the full moon and new moon respectively. Since the Moon’s orbit is tilted just over five degrees from the ecliptic, we have to wait for the intersecting nodes to line up for an eclipse season to occur, which happens roughly twice a year. This also means that eclipses occur in lunar-solar pairs. In the case of the upcoming eclipse season, Monday’s penumbral lunar eclipse is followed by a total solar eclipse that crosses the southern tip of South America on December 14.

Tales of Saros

Furthermore, lunar and solar eclipses are members of a larger period of 18 years, 11 days, and 8 hours known as saros. This works because 223 synodic lunations (the length of time it takes the Moon to return to the similar phase, i.e. from full to full or from new to new) is almost equal to saros. This also means that successive eclipses with very similar circumstances occur at a distance of one saros, with the visibility path shifted 120 degrees of longitude to the west. Several sarosi, both lunar and solar, are at stake in any given year. In the case of Monday’s penumbra, this eclipse is a member 58 of 73 eclipses in the 116 series of lunar saros, which began in 933 AD on March 11 and extends to 2291. Saros 116 also produced its last total lunar eclipse in July 11th, 1786 and is now coming out the door, with a final superficial penumbral eclipse that occurred on May 14, 2291.

Why do penumbral pains occur? Why doesn’t the Earth cast a sharp and distinct shadow into space? This double shadow has to do with the nature of light and the fact that the Sun is not a point source: it is actually visually very close to the apparent size of the Moon as seen from Earth, as witnessed during a total solar eclipse. See this secondary shadow effect every day, in places like a room lit only by a window on one side – once you know you are looking for them, half-light shadows are literally everywhere.

Here’s another way to think about it: When you’re witnessing a partial solar eclipse, you’re also in the twilight shadow of the Moon. Similarly, standing on the near side of the Moon on Monday morning and looking back towards Earth (with adequate eye protection, of course), you would see a partial solar eclipse.

It turns out that a newcomer will indeed be on the Moon, assuming it lands successfully: the Chinese Champion Return Mission Chang’e 5, which will land in Mon Rümker in the Oceanus Procellarum region this weekend. It is unknown if the team is planning to photograph the partial solar eclipse (or even if it needs to be able to), but this possible view from the surface of the Moon would be the first.

Here’s a fun naked-eye observation to make during a twilight eclipse: Close the Full Moon right near the middle of the “penumbrality …” Would you notice something is going on, if you didn’t know better? Can you spy on the jagged edge of the shadow, trying in vain to devour the Moon? Perhaps a lux or colorimeter (common on many smartphones nowadays) could detect the slight difference in brightness and tint during a penumbral eclipse.

A more direct way to “see” the eclipse is to simply imagine the Moon before, during and after the eclipse, using the exact same camera and settings … does the photo in the middle of the eclipse look noticeably different to you?

Fear not: the drought of the total lunar eclipse is almost over. While 2021 has only four eclipses (the minimum that occurs in a solar year, which must be 2 lunar and 2 solar), we actually have a total lunar eclipse on May 26, in favor of the Pacific region.

If the skies are clear, be sure to set your alarm for the “penultimate twilight eclipse” of 2020.

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