Useful Projects for a Lunar Eclipse

Amateur astronomers typically plan how they will take pictures, picture sequences, and even time-lapse movies of a lunar eclipse. But do not overlook the scientifically helpful initiatives which can be simply begging to be carried out. You do not want something however clear skies and a few quite simple gear.


Total lunar eclipses are available in a nice number of brightnesses and hues. In February 1860, Irish novice Mary Ward likened the Moon to “a red-hot penny” within the sky. But the famously darkish eclipse of December 1963 was so dim that some skywatchers couldn’t discover the Moon once they stepped outdoor close to mid-totality!

To assist in evaluating stories from varied observers, even years and cultures aside, French astronomer André Danjon devised a five-point scale that’s nonetheless used in the present day. As proven beneath, the Danjon values vary from 0 (Moon nearly invisible at mid-totality) to 4 (very shiny copper-red or orange Moon). To learn to give this eclipse a Danjon L ranking, go here.

Danjon scale of totality brightness
Use this five-step Danjon scale to evaluate the darkness of the Moon throughout a complete lunar eclipse.
Leah Tiscione / Sky & Telescope


For many years Brazilian astronomer Helio C. Vital has led a very lively group of observers in monitoring the brightness of the eclipsed Moon, not solely because it strikes throughout the shadow but in addition from one eclipse to the subsequent. For instance, he is discovered that a complete eclipse is pretty shiny if it takes place when Earth’s environment is sort of freed from aerosols. But inside a few years after a main volcanic eruption, eclipses are sometimes a lot darker. Some darkening was even detected after the October 6, 2006, eruption of Mount Rabaul in Papua New Guinea.

So how do you make an estimate? If you put on thick glasses you may attempt taking them off so the Moon and shiny planets or stars appear to be equal-size blobs. A greater method is to have a look at the Moon by way of the flawed finish of binoculars, and to check its brightness seen that way with varied shiny stars seen with out optical support. Do this at common intervals because the Moon crosses the umbra, and in your report you’ll want to point out the ability of the binoculars and which comparability stars you used.

Crater Timings — Measuring the Size of the Umbra

Lunar craters for timing
By timing to the closest 5 seconds when a few distinguished craters and spots cross Earth’s shadow, you may assist Sky & Telescope gauge the dimensions of Earth’s silhouette (see finish of weblog). Click on picture for a bigger view.
Gary Seronik

Timings of celestial occasions supplied early mariners a way to seek out their longitude removed from residence. This technique was utilized by Christopher Columbus, who timed the beginning and finish of a lunar eclipse in 1504 throughout his fourth journey to the New World.

When astronomers tried to refine this technique, nevertheless, they rapidly discovered that the darkish heart of the Earth’s shadow, known as the umbra, was bigger than pure geometry indicated by about 2%, as a result of our environment provides to Earth’s efficient diameter.

To time when the Moon’s edge enters or leaves the shadow is usually iffy. Instead, it is extra correct to time when particular person spots and craters cross the shadow’s edge. For instance, from 697 crater timings despatched in by Sky & Telescope readers, I derived an enlargement of two.1% for the July 1982 eclipse. But for a comparable occasion solely six months later, 298 timings gave 1.7% enlargement. In every case the possible error was lower than 0.1%. So the enlargement undoubtedly varies barely from eclipse to eclipse, for causes not but understood.

The Moon photograph above has distinguished options labeled; click on the picture for a bigger model to print out and take with you to the telescope. Sky & Telescope predictions of those options’ entrance and exit instances within the umbra throughout the upcoming eclipse are given within the desk beneath; it’s also possible to download a PDF version.

S&T ’s Eclipse-Timing Predictions for the Total Lunar Eclipse – May 26, 2021

Entry (UT) Exit (UT)
Grimaldi 9:52 Harpalus 11:38
Billy 9:53 Aristarchus 11:48
Campanus 9:57 Plato 11:50
Tycho 10:00 Grimaldi 11:53
Birt 10:05 Pico 11:53
Kepler 10:07 Kepler 11:57
Copernicus 10:14 Pytheas 12:00
Aristarchus 10:15 Aristoteles 12:01
Pytheas 10:21 Billy 12:01
Dionysius 10:26 Timocharis 12:01
Timocharis 10:28 Copernicus 12:05
Manilius 10:29 Eudoxus 12:05
Censorinus 10:31 Campanus 12:14
Goclenius 10:31 Manilius 12:19
Menelaus 10:32 Birt 12:21
Plinius 10:35 Menelaus 12:21
Langrenus 10:36 Tycho 12:24
Taruntius 10:38 Plinius 12:26
Harpalus 10:42 Dionysius 12:28
Pico 10:43 Proclus 12:35
Proclus 10:43 Censorinus 12:36
Plato 10:47 Taruntius 12:40
Eudoxus 10:48 Goclenius 12:44
Aristoteles 10:52 Langrenus 12:48
These lunar craters might be coated and uncovered by the sting of Earth’s umbra throughout the upcoming eclipse
Roger Sinnott / Sky & Telescope

Before making your timings, set a watch to correct Internet time or use a time app that shows seconds in your cellphone. Write down the time (to the closest 5 seconds) when the sting of the umbra crosses the heart of the crater or different characteristic.

It’s so simple as that! The shadow edge is a little fuzzy, so attempt to decide the a part of the shadow-edge the place the sunshine falls off most quickly, and undertake that for your timings.

It’s greatest to make use of a scope with an aperture of not less than 2.4 inches (60 mm), however no more than 8 inches (200 mm). The entire level is to make timings the identical way they have been performed for 300 years, so outcomes could be in contrast.

If you perform any of those easy initiatives on the subsequent eclipse of the Moon, please e-mail the outcomes to me. I’m accumulating them for later evaluation.

But it doesn’t matter what you do, put aside a little time to take a seat again and benefit from the eclipse, too!

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