This is the Classical Astronomy Update, an email newsletter especially
for Christian homeschool
families (though everyone is welcome!) Please feel free to share this with any interested friends.
Blessed of the Lord be his land, for the precious things of heaven, for the
dew, and for the deep that coucheth beneath, and for the precious fruits
brought forth by the sun, and for the precious things put forth by the
moon. - From Moses' blessing of Joseph, Deuteronomy 33:13b-14
IN THIS UPDATE
Sunrise Total Lunar Eclipse - Western USA - May 26
Sunrise Partial Solar Eclipse - Eastern USA - June 10
Hello Friends,
As promised last week, here's the next newsletter discussing the lunar and solar eclipses visible at sunrise from the USA over the next couple weeks. There's a lot of ground to cover so we'll dive right in.
Please invite your friends and family to participate in the webinars, including your church, homeschool co-op or anyone you know who might be interested. There will be plenty of available slots and everyone is welcome.
For more information about topics from Classical Astronomy
discussed in this newsletter, please check out
a homeschool astronomy curriculum
(but popular with adult readers too!)
Visit our archive of previous editions of the Classical Astronomy Update newsletters, going back to 2007.
*****
Sunrise Total Lunar Eclipse - Western USA - May 26
There will be a total lunar eclipse on Wednesday, May 26, 2021. The Moon will be over the Pacific Ocean during the partial and total phases so this eclipse is ideally placed for New Zealand, Australia and the nations of the western rim of the Pacific.
However, the eclipse will be observable before sunrise for earlybirds in most parts of the USA. More of the eclipse will be visible out west and less will be seen back east. We'll get to the details but first a little background....
Earth's Shadow - Redux
Last week's newsletter explained how you can see the Earth's shadow after sunset. A lot of readers were intrigued by this concept and I got more response than usual. If one has a flat horizon free of trees and mountains, it's actually very common to see the Earth's shadow after the Sun
sets, rising up in the east at the opposite positon from the sunset.
It is also similarly true that the Earth's shadow can also be seen in the west before sunrise. About 10-15 minutes before the Sun rises, the dark arc of the Earth's shadow appears out of the brightening dawn sky, and descends toward the western horizon as the Sun rises toward the eastern horizon. The shadow arc sinks out of sight as the Sun's rays break forth into the morning sky.
In both cases, before sunrise and after sunset, you see the dark grey arc when your location is within the Earth's shadow, or umbra. As you look in the opposite direction from the Sun, you can see a dark portion of the atmosphere where the body of the Earth blocks the Sun's rays. Above that portion, you can see a brighter sky above the dark arc where the Sun's rays are shining, lighting up the air.
The shadow arc is curved, following the curvature of the Earth. This is one of many proofs that the Earth is round, and flat earth adherents are at a loss to explain a curved shadow according to their mistaken belief.
For this reason, we can all observe the dark bluish-gray arc of the Earth's shadow below the brighter sunlit sky at the anti-solar point on the opposite horizon from the Sun, as explained in last week's newsletter. In this manner, we can directly observe the Earth's umbra when we are inside of it
when the Sun is just below the horizon.
From locations in the Arctic, it should be possible to see the Earth's shadow circle around the horizon opposite the Sun during times and places where strong twilight persists throughout the night, when the Sun is within 5 degrees below the horizon. Try to notice this during the summer if you live in Alaska or other high latitude locations.
Eclipses and the Earths' Shadow
The Moon passes through the Earth's umbra during a partial and total lunar eclipse. This is another instance of how the Earth's umbra might be observed. During the May 26 lunar eclipse, Americans will have the rare opportunity to observe the Earth's umbra at sunrise while also observing the umbra upon the Moon during partial and total phases.
The Moon enters the Earth's umbra during ingress, which is the "incoming" phase of partial eclipse. During ingress, the Moon's orbital motion carries it more deeply into the umbra, and the partial phase increases as more of the Moon's sphere is obscured by the umbra. The Earth's umbra again appears curved during ingress, proving again that it is a round shadow of a round Earth.
Sometimes there is only a partial lunar eclipse when the Moon only grazes the umbra. Other times there is a total lunar eclipse when the Moon is fully immersed in the umbra. There is a first partial phase during ingress, a phase of totality, and a second partial phase during egress, when the Moon is emerging from the Earth's umbra.
During totality, the Moon can still be visible as having a dusky reddish glow. Sometimes this glow is very faint and the Moon is dark and barely visible. Other times the Moon appears quite bright with only a shade of a copper glow upon its face.
This eclipse coloration is due to the same orange glow seen at sunrise and sunset. The Earth's atmosphere scatters out all the colors of the sunlight except the red and orange shades. These ruddy sunset rays pass through the atmosphere and out into space.
This same orange-red glow shines toward the Moon when the Sun's bright light is blocked by the Earth, and shines upon the Moon's surface. If one could be on the Moon, one would see an orange-red glowing ring around the Earth representing the sunrise and sunset, and that ring casting a rosy light upon the lunar landscape. Perhaps someday future astronauts will witness such an incredible sight for
themselves. (These eclipse images are adapted from Eclipses Illustrated, Book 1.)
The May 26 Eclipse
Here's the timing of next Wednesday's eclipse:
Ingress begins at First Umbral Contact (U1)
5:45 AM EDT
4:45 AM CDT
3: 45 AM MDT
2:45 AM PDT
Ingress ends and totality begins at Second Umbral Contact (U2)
7:11 AM EDT
6:11 AM CDT
5:11 AM MDT
4:11 AM PDT
Totality ends and egress begins at Third Umbral Contact (U3)
7:26 AM EDT
6:26 AM CDT
5:26 AM MDT
4:26 AM EDT
Egress ends at Fourth Umbral Contact (U4)
8:52 AM EDT
7:52 AM CDT
6:52 AM MDT
5:52 AM PDT
As you can see, totality for this eclipse will be very short, only 11 minutes, and very likely the umbra will not be very dark upon the Moon. Also notice that most of the above umbral contacts will occur after the Sun rises in most American locations, especially those to the east.
To me, the interesting thing about this eclipse is that American observers in the eastern USA should be able to see the eclipsed Moon appearing within the Earth's shadow at totality or partial phase in the short minutes before sunrise and moonset, as seen in this image. This is like a double whammy of observing the Earth's umbra, seeing the umbra upon the Moon and also in the atmosphere at the same time!
(I've never seen this or heard a report of such a thing, so this is a type of experiment. But please report back if you do observe this double umbral phenomenon!)
The view you might see depends entirely on where you are in the USA.
There will be nothing to see if you live in the northeast, in New England or the East Coast cities, so you can stay in bed and not worry about this eclipse. (But don't feel bad, you'll have a great show for the June 10 sunrise partial solar eclipse, discussed in the next section below.)
If you live in the large swath of America from the Great Lakes and Mississippi basin down through the southeast and the Gulf of Mexico, you can expect to see the Moon setting during ingress. In the above image, you can expect to see the Moon with a shaded portion of the umbra viewed within the Earth's shadow.
Wherever you live, you can get an idea of how much eclipse you can expect by looking up the sunrise and moonset times for your area. Compare the above times for the umbral contacts with the times of sunrise and moonset.
For example, where I live in Cleveland, Ohio, the Sun rises at 5:58 AM on May 26, 13 minutes into ingress. The Moon sets at 6:02 AM that day. So I might expect to see a very shallow phase of partial eclipse within the Earth's shadow before the Moon disappears below the horizon. But seeing the uncommon sight of the Moon within the Earth's shadow will be the draw for me.
If you're in the "Goldilocks zone" within the central USA, you will see all of ingress during dawn twilight, and can hope to see the totally eclipsed Moon setting within the Earth's shadow just before sunrise. If you reside along a very narrow path of fortunate observers, you can look for the elusive selenion, a very rare phenomenon (details below).
Most of the western states between Mexico and Canada can see all of totality with an egressing partially eclipsed Moon setting within the Earth's shadow. California and the southwest tip of Oregon will see the whole show, all of totality and both partial phases.
As for selenion, it is a rare and elusive phenomenon when the rising Sun and the totally eclipsed Moon are visible above the horizon at the same time in the blue sky. I saw selenion once maybe 10 or 15 years ago.
Selenion is supposed to be impossible according to sky geometry since eclipses can only occur at the Full Moon, which is completely at the 180 degree opposite position from the Sun in the sky. So when the Sun is up, the Full Moon is down, or is supposed to be. However, this is not strictly the case due to refraction in the Earth's atmosphere.
Basically, the atmosphere acts as a lens and bends the rays of light from the Sun and Moon, causing them to still appear above the horizon when they should appear below.
Refraction of the stars is an inflexion of the rays of those luminaries in passing through our atmosphere, by which their apparent altitudes are increased. – Nathaniel Bowditch (A.D. 1802)
Refraction causes an optical illusion in which the Sun and Moon appear about one degree higher than they should, about two solar or lunar diameters above their physical, geometrical positions in the sky.
When the Sun is near the Horizon it appears higher than really it is by reason of the Refraction or breaking of its Rays in passing through a larger Space of Atmosphere or thicker Air. When the Sun is one Degree high its Refraction causes it to appear near half a Degree higher than it is. – Isaac Watts (A.D. 1726)
(The subject of refraction will be discussed in detail in Measuring the Heavens, the upcoming sequel to our Signs & Seasons homeschool
astronomy curriculum.)
Selenion was observed in ancient times and puzzled the Ancient Greeks, who originally developed the geometrical system of the sky. This "paradoxical eclipse" represented the basic discovery of atmospheric refraction and thereby advanced the development of science.
For some say that a lunar eclipse occurs even when both luminaries are observed above the horizon.... Since there are by nature a wide variety of conditions that affect the air, it would not be impossible for us to encounter an image of the Sun as not yet having set after it had already set (that is, after it was below the horizon).... But the ray that flows out from the eyes could also be refracted on
encountering air that is damp and moist, and encounter the Sun after it is already concealed below the horizon... Something similar could, then, occur with damp and sodden air too, so that when the ray from the eye is refracted and bends below the horizon, it encounters a Sun that has already set, so that an image of it is engendered as still being above the horizon. Perhaps something else much like this could also on occasion produce an image in us of the two [heavenly] bodies being above the
horizon after the Sun has already set. – Cleomedes (circa 200 B.C.)
Selenion is not actually rare since it happens with every eclipse. But as with any atmospheric effect, it varies with the weather and can be greater or lesser depending on meteorological factors. And not every selenion passes over land where it can be observed. So observations of selenion are rare even though the phenomenon is not.
So please let us know if you are fortunate enough to observe selenion on the morning of Wednesday, May 26! If you can, try to snap a picture of the totally eclipsed Moon above the horizon during daytime and we'll share it!
Sunrise Partial Solar Eclipse - Eastern USA - June 10
Every year there are two eclipse seasons. Eclipses occur when the Sun is near the nodes of the Moon's orbit. So solar and lunar eclipses always come at least in pairs every eclipse season, sometimes in threes. A solar eclipse is always preceded or succeeded by a lunar eclipse, two weeks apart. However, it might not be obvious at a glance since each of these eclipses are usually
seen in different parts of the globe. But North America is favored in the eclipse season of May/June, 2021.
The total lunar eclipse that occurs at the Full Moon on Wednesday, May 26 is followed by an annular solar eclipse that occurs at the New Moon on Thursday, June 10. There will be another eclipse season in another half year when the Sun again lines up with a lunar node. There will be a nearly-total lunar eclipse on November 19 favoring the USA and a total solar eclipse over
Antarctica on December 4. I expect to report on the lunar eclipse closer to that time.
An annular eclipse is a "ring eclipse" in which the Moon appears smaller than the Sun and does not fully cover over the Sun's disc. Annulars are not as famous to the general public since they are only a type of partial eclipse and nowhere as impressive as a total eclipse of the Sun. However, annular eclipses are actually more common than total solar eclipses, though they usually do not get much
publicity.
Annularity will not be seen over the USA, though it will be seen over Canada, the North Pole and into far eastern Siberia, as shown in the graphic below. However, if one wishes to brave the mosquitoes in a remote area of Ontario, Canada along Lake Superior and Lake Nipigon, one could expect to see a "ring of fire" annular eclipse at sunrise on the morning of June 10.
Those of us staying at home that morning can expect to see a partial solar eclipse at sunrise on that day. But be warned, you'll want to have solar viewing glasses to see this interesting sight. They can be ordered from many places, including the website of Mike Kentrianakis, America's
Favorite Eclipse Chaser. (Classical Astronomy will not be selling them this time.)
While the eastern USA will miss out on the sunrise total lunar eclipse, it'll be the best place to be stateside for the sunrise partial eclipse. In the northeast, in New England and the East Coast big cities, ingress will be underway as the Sun rises. You can expect to the longest duration of partial solar eclipse, but the partial phase will not be so great at sunrise. If the morning air is thick enough
so that the Sun comes up big and orange, you might be able to safely watch the partially-eclipsed sunrise. However, you'll really need those eclipse glasses if you want to continue watching the partial eclipse when the Sun brightens after sunrise.
If you're along a line stretching from the Great Lakes to the Jersey Shore, you can expect to see the maximum phase of partial eclipse at sunrise. This promises to be the best show if you want to be wowed by a most unforgettable sunrise.
I've seen a sunset partial eclipse over Lake Erie at Cleveland, Ohio and it is a very cool sight, a red and otherworldly crescent Sun along the horizon. Observers along the Great Lakes and the ocean can expect a similar sight at sunrise on June 10.
(If you live in the Cleveland area, I'm planning on being along Lake Erie at Lakewood Park for a 5:54 AM sunrise. Drop me a line if you want to meet up.)
Here's that sunrise link again to find the time in your area.
If you're south and west of that maximum sunrise line, from the Dakotas to the Carolinas, you can expect to see the egress phase of partial solar eclipse at sunrise. It's still worthwhile to check it out, especially if you have a clear, flat horizon since the eclipse will end not long after sunrise. And you'll still want those eclipse glasses.
Order early since quantities are ALWAYS limited for every eclipse, and they ALWAYS sell out.
If you live at points west, sorry! The eclipse will be over before the Sun rises in your area. But there'll always be other eclipses. Be sure to enjoy your prime sight of the lunar eclipse.
The above image is from our friends at GreatAmericanEclipse.com. Click on the image for more detailed information about this eclipse. Also check out this interactive NASA web page that will give you technical information about this eclipse as it applies to your home or any area of interest.
If anyone sends any cool pix of the solar and/or lunar eclipse(s), we'll put out another newsletter sometime soon thereafter. We can also post any cool pix on the Classical Astronomy group at MeWe.
Til next time, God bless and clear skies,
- jay
The Ryan Family
Cleveland, Ohio, USA
When I consider thy heavens, the work of thy fingers, the moon and
the stars, which thou hast ordained, what is man that thou art
mindful of him? and the son of man, that thou visitest him?
- Psalm 8:3-4, a Psalm of David
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