harvest moon eclipse Archives

So, heard the one about this weekend’s impending ‘Super-Harvest-Blood-Moon eclipse?’ Yeah, us too. Have no fear; fortunately for humanity, the total lunar eclipse transpiring on Sunday night/Monday morning is a harbinger of nothing more than a fine celestial spectacle, clear skies willing.

This final eclipse of the ongoing lunar tetrad has some noteworthy events worth exploring in terms of science and lore.

The Supermoon Total Lunar Eclipse of September 27-28 2015 from Michael Zeiler on Vimeo.

The Specifics: First, you almost couldn’t ask for better timing. This weekend’s total lunar eclipse occurs during prime time Sunday night for North and South America, and early Monday morning for Europe, Africa and most of the Middle East. This means the Atlantic Region and surrounding areas will see totality in its entirety. This eclipse occurs very near the northward equinoctial point occupied by the Sun during the Northern Hemisphere Spring equinox in March. The date says it all: this eclipse coincides with the Harvest Moon for 2015, falling just under five days after the September equinox.

Early cloud cover prospects for Sunday night over the contiguous United States. Image credit: The National Weather Service

For saros buffs, Sunday’s eclipse is part of lunar saros series 137, member 28 of 81. This saros started back in 1564 and produced its first total lunar eclipse just two cycles ago on September 6^th 1979. Saros 137 runs all the way out to its final eclipse on April 20^th, 2953 AD.

And yes, this upcoming total lunar eclipse occurs very near the closest lunar perigee for 2015. How rare are ‘Supermoon’ lunar eclipses? Well, we took a look at the phenomenon, and found 15 total lunar eclipses occurring near lunar perigee for the current century:

Perigee eclipses for the 21st century. To make the cut, a total lunar eclipse needed to occur within 24 hours of lunar perigee. Image credit: Dave Dickinson

You’ll note that four saroses (the plural of saros) are producing perigee or ‘Proxigean’ total lunar eclipses during this century, including saros 137.

Does the perigee Moon effect the length of totality? It’s an interesting question. Several factors come into play that are worth considering for Sunday night’s eclipse. First, the Moon moves a bit faster near perigee as per Kepler’s second law of motion. Second, the Moon is a shade larger in apparent size, 34’ versus 29’ near apogee. Lastly, the conic section of the Earth’s shadow or umbra is a bit larger closer in; you can fit three Moons side-by-side across the umbra around 400,000 kilometers out from the Earth. Sunday night’s perigee occurs 65 minutes after Full Moon at 2:52 UT/10:52 PM EDT. Perigee Sunday night is 356,876 kilometers distant, the closest for 2015 by just 115 kilometers, and just under 500 kilometers short of the closest perigee that can occur. This is, however, the closest perigee time-wise to lunar totality for the 21^st century; you have to go all the way back to 1897 to find one closer, at just four minutes apart.

Now, THAT was and eclipse!

This all culminates in a period for totality on Sunday night of just under 72 minutes in duration, 35 minutes shy of the maximum possible for a central total lunar eclipse. An eclipse won’t top this weekend’s in terms of duration until January 31^st 2018.

Here are the key times to watch for on Sunday night:

Penumbral phase begins: 00:12 UT/8:12 PM EDT (on the 27^th)

Partial phase begins: 1:07 UT/9:07 PM EDT

Totality begins: 2:11 UT/10:11 PM EDT

Totality ends: 3:23 UT/11:23 PM EDT

Partial phase ends: 4:27 UT/00:27 AM EDT

Penumbral phase ends: 5:22 UT/1:22 AM EDT

Note that one 18 year 11 day and 8 hour saros period later, saros 137 will again produce a perigee eclipse nearly as close as this weekend’s on October 8^th, 2033.

The classic hallmark of any total lunar eclipse is the reddening of the Moon. You’re seeing the combination of all the world’s sunsets, refracted into the inky umbra of the Earth and cast upon the surface of the Moon. To date, no human has stood upon the surface of the Moon and gazed upon the spectacle of a solar eclipse caused by the Earth.

Not all eclipses are created equal when it comes to hue and color. The amount of dust and aerosols suspended in the atmosphere can conspire to produce anything from a bright, yellowish-orange tint, to a brick dark eclipse where the Moon almost disappears from view entirely. The recent rapid fire tetrad of four eclipses in 18 months has provided a good study in eclipse color intensity. The deeper the Moon dips into the Earth’s shadow, the darker it will appear… last April’s lunar eclipse was just barely inside the umbra, making many observers question if the eclipse was in fact total at all.

We the describe color of the eclipsed Moon in terms of its number on the Danjon scale, and recent volcanic activity worldwide suggests that we may be in for a darker than normal eclipse… but we could always be in for a surprise!

Old time mariners including James Cook and Christopher Columbus used positional measurements of the eclipsed Moon at sea versus predictions published in almanac tables for land-based observatories to get a one-time fix on their longitude, a fun experiment to try to replicate today. Kris Columbus also wasn’t above using beforehand knowledge of an impending lunar eclipse to help get his crew out of a tight jam.

And speaking of the next perigee Moon total lunar eclipse for saros 137 on October 8th, 2033… if you catch that one, this weekend’s, and saw the September 16^th, 1997 lunar eclipse which spanned the Indian Ocean region, you’ll have completed an exeligmos, or a triple saros of eclipses in the same series 54 years and 33 days in length, an exclusive club among eclipse watchers and a great word to land on a triple letter word score in Scrabble…

Exeligmos is also the title of one of our original scifi tales involving eclipses, along with Shadowfall.

Here’s another neat challenge: the International Space Station makes two shadow passes during the lunar eclipse over the contiguous United States. The first one occurs during totality, and spans from eastern Louisiana to central Maine from 2:14 to 2:20 UT; the second pass occurs during the final partial phases of the eclipse spanning from southern Arizona to Lake Superior from 3:47 to 3:54 UT. These are un-illuminated shadow passes of the ISS. Observers have captured transits of the ISS during a partial solar eclipse, but to our knowledge, no one has ever caught a transit of the ISS during a total lunar eclipse; ISS astros should also briefly be able to spy the eclipsed Moon from their orbital vantage point. CALSky will have refined passage times about 48 hours prior to Sunday.

Clouded out? Live on the wrong side of the planet? The good folks at the Virtual Telescope Project have got you covered, with a live webcast of the total lunar eclipse starting at 1:00 UT/9:00 PM EDT.

And as the eclipse draws to an end, the question of the hour always is: when’s the next one? Well, the next lunar eclipse is a dim penumbral on March 23^rd, 2016, which follows a total solar eclipse for southeastern Asia on March 9^th, 2016… but the next total lunar won’t occur until January 31^st, 2018, which also happens to be the second Full Moon of the month… a ‘Blue Blood Moon Eclipse?’

Sorry, we had to go there. Hey, we could make the case for Sunday’s eclipse also occurring on World Rabies Day, but perhaps a ‘Rabies Eclipse’ just doesn’t have the SEO traction. Don’t fear the Blood Moon, but do get out and watch the final lunar eclipse of 2015 on Sunday night!

Think you know the Moon? Whether you love our natural neighbor in space for the lunar and solar eclipses it provides, or you simply decide to ‘pack it in’ from deep sky observing on the weeks bookending Full phase — per chance to catch up on image processing — the Moon has provided humanity with a fine crash course in Celestial Mechanics 101.

Take the Moon’s path in the Fall of 2015 as a peculiar case in point. In fact, we’re nearing what’s known as a minor lunar standstill over the next lunation, the first of the 21^st century.

The term lunar standstill is kind of a misnomer. The Moon will continue in its orbit around the Earth like it always does. What’s interesting to note, however, is how shallow the apparent path of the Moon currently is with respect to the ecliptic this year. A technical lunar standstill – the point at which the Moon seems to reverse course from north to south and vice versa – occurs twice a lunation… but not all lunar standstills are created equal.

The approximately five degree tilt of the Moon’s path around the Earth with respect to the path of the Earth around the Sun assures that the Moon can actually appear anywhere from 23.5 degrees (the tilt of the Earth’s axis with respect to the ecliptic) plus five degrees above or below the celestial equator, or 28.5 degrees declination north to south.

Such a ‘hilly year’ happens once every 18.6 years, and last occurred in 2006, and won’t take place again until 2025. This orbital phenomenon also results in what’s known as a ‘long nights moon’ when the Full Moon nearest the winter solstice rides high in the sky near the spot the summer Sun occupied six months earlier, and will do so again six months hence.

To quote Game of Thrones: “Winter is coming,” indeed.

Aspects of major a minor lunar standstill years. Note: node crossing refers to the date that the ascending/descending node of the Moon equals an ecliptic value of zero, while the actual dates refer to the times of greatest declination. Image credit: Dave Dickinson

Such is the wacky orbit of the Moon. Unlike the majority of natural satellites in the solar system, the inclination of the Moon’s orbit is not fixed in relation to its host planet’s (in this case, the Earth’s) equator, but instead, to the plane of its path around the Sun, that imaginary line known as the ecliptic. Hence, we say the Moon’s path is either steep and ‘hilly’ near a major lunar standstill, or shallow and almost flat-lined, like this year. In between years are sometimes termed ‘ecliptic-like’ and happen between standstills once every 9.3 years.

Why are the nodes of the ecliptic changing? The chief culprit is the gravitational pull of the Sun, which drags the nodes opposite in the Moon’s direction of travel once around full circle every 18.6 years. To confound things even more, the Moon’s line of apsides (the imaginary line bisecting its orbit from apogee to perigee) is moving in the opposite direction and completes one revolution every 8.85 years.

This also means that the Moon can wander off the beaten trail of the zodiac constellations well worn by the classical planets. The Moon can actually transit 18 constellations: the 12 familiar zodiacal constellations, plus Orion, Ophiuchus, Sextans, Corvus, Auriga and Cetus.

This, along with the 26,000 plus year precession of the equinoxes, also means that the stars the Moon can occult along its path are slowly changing as well.

There’s lots of evidence to suggest that ancient astronomers knew something of the cycle of lunar standstills as well. The modern term comes from archaeologist Alexander Thom’s 1971 book Megalithic Lunar Observatories. There is evidence to suggest Bronze Age cultures in the United Kingdom took note of the changing path of the Moon. The famous ‘Sun dagger’ rock alignment of Fajada Butte in Chaco Canyon, New Mexico may have also doubled as a similar sort of calendar that not only marked the yearly solstices and equinoxes, but longer periods of the cycles of the Moon as well.

Knowing the gear clock tick of the heavens gave cultures an edge, allowing them to predict when to sow, reap, hunt and prepare for the onset of winter.

The 2015 minor lunar standstill also impacts this years’ Full Harvest Moon as well. Ordinarily on most years, the evening angle of the ecliptic versus the eastern horizon near the autumnal equinox conspires to make the Moon seem to ‘freeze’ in its nightly path, rising scant minutes later on successive evenings. This effect is most dramatic as seen from mid-northern latitudes in September on years around the major lunar standstill.

Not so in 2015. The Full Harvest Moon occurs on September 28^th at 2:50 UT (10:50 PM EDT on the evening of the 27^th) about four and half days after the autumnal equinox. As seen from latitude 40 degrees north, however, the Moon will rise nearly 40 minutes later each successive evening. Check out these Moonrise times as seen from the U.S. capital near 39 degrees north latitude:

Washington D.C.

Sept 25^th 5:28 PM

Sept 26^th 6:09 PM

Sept 27^th 6:49 PM

Sept 28^th: 7:29 PM

Sept 29^th: 8:11 PM

As you can see, the minor lunar standstill of 2015 ameliorates the usual impact of the Harvest Moon… though we do have the final total lunar eclipse of 2015 to compensate.

Tag: harvest moon eclipse

Sunday Night: Getting Ready For a ‘Super-Harvest-Blood-Moon Total Lunar Eclipse’

A Minor Lunar Standstill for 2015