A slender partial lunar eclipse bookends the final eclipse season of 2023.
Checking out the October Hunter’s Full Moon this coming weekend? This Full Moon is also special, as it features the final eclipse of 2023. The eclipse is a partial lunar, and occurs on the night of Saturday/Sunday, October 28th/29th.
The eclipse is a partial teaser, with the Moon juuuust skimming the inner dark umbral cone of the Earth’s shadow. Maximum partial phase is 12%, with the inner ragged umbral core of the Earth’s shadow cast across the southeastern limb of the Moon.
Timing and Circumstances for the Eclipse
The entirety of the eclipse favors Africa, Europe and Asia. Australia will see the eclipse underway at moonset. The Canadian Maritimes and the very eastern tip of Brazil will see the eclipse afoot at moonrise.
Key times for the eclipse (in Universal Time) are:
Penumbral start: 18:02 UT
Umbral start: 19:35 UT
Mid-eclipse: 20:15 UT
Umbral end: 20:53 UT
Penumbral ends: 22:26 UT
The overall eclipse is 4 hours and 25 minutes long, and the umbral phase is 1 hour and 17 minutes long. Expect to start seeing some penumbral discoloration as a tea-colored shading on the Moon about 30 minutes in. The darker, jagged edge of the shadow will take a bite out of the Full Moon around the beginning of the umbral phase.
Why Eclipse Seasons Occur
Eclipses occur when the Sun, Earth and Moon align, known as a syzygy. The Moon’s orbit is inclined just a little over five degrees relative to the ecliptic plane, meaning that the Sun and Moon must be near where the nodes where the ecliptic and the Moon’s orbit intersect for eclipses to occur. Generally, this happens twice a year. An eclipse season happens with one solar eclipse and one lunar, about two weeks apart. This weekend’s eclipse ends season two of two for 2023, which kicked off with the annular solar eclipse on October 7th.
If you watch eclipses long enough, you’ll notice the pattern repeats, with an eclipse pattern repeating for a given location once every 54 years. This is an exeligmos, a period equal to three saros cycles. A saros cycle is 18 years, 10-12 days (depending how leap years fall) and 8 hours long, equal to 223 synodic lunar periods. That eight hour bit is important, as it shifts the eclipse circumstances 120 degrees east in longitude, bringing the eclipse cycle back around every three saroses.
Eclipses both lunar and solar all belong to saros families, each over a thousand years long. Several saroses are active on any given year, as they slowly evolve, become more central and feature totality, and then fade out.
Tales of the Saros
This coming weekend’s eclipse is a member of lunar saros series 146, member 11 of 72 eclipses. This saros is a relatively new one astronomically speaking, having just started on July 11th 1843, and running all the way out to August 29th, 3123 AD. The eclipse also occurs just over 17 hours after the the Moon crosses ascending node, which is why the Moon just nicks the Earth’s umbral shadow.
If you caught the October 17th, 2005 partial eclipse visible from the Pacific region, you saw the last eclipse in this saros. Saros 146 will begin to produce total lunar eclipses on (mark your calendars) May 25th, 2366 AD.
You can also catch the eclipse live from Rome Italy on the night of Saturday, October 23rd starting at 18:00 UT/2:00 PM EDT courtesy of astronomer Gianluca Masi and the Virtual Telescope Project.
Eclipses have long been seen as omens of ill or harbingers of bad fortune. Certainly, there are enough lunar eclipses visible every year from the Moonward-facing hemisphere of the Earth that it’s never a problem to find a current catastrophe to tie one to. A partial lunar eclipse was seen on May 22, 1453, a week prior to the fall of the city of Constantinople to the Ottomans. The eclipse was a deep 75% partial, with the eclipse already underway at dusk with the Moon rising to the east. This was said to fulfill an ancient prophecy stating that the empire would stay whole as long as the Moon was whole. A convenient eclipse omen for the besiegers maybe, but not the besieged.
The View From the Moon
Of course, when you’re seeing a lunar eclipse from the Earth, you would see a solar eclipse while standing on the Earthward surface of the Moon. Most of the Moon will witness a partial solar eclipse on Saturday night, though the extreme southern polar region will witness totality. This also includes the recent landing site for India’s Chandrayaan-3 Vikram lander and Pragyan rover at Shiv Shakti Point near Manzinus C and Simpelius N craters. Unfortunately, both have fallen silent, having succumbed to the cold lunar night.
Perhaps one day, human explorers will witness the glory of a total solar eclipse from the Moon.
Eclipses in 2024: A Teaser
That’s it for eclipses in 2023. Next year features four eclipses (the minimum that can occur in a calendar year) two solar and two lunar:
-A penumbral lunar eclipse on March 25th, (87%) for the Americas.
-A total solar eclipse for April 8th, 2024 for North America
-A partial lunar eclipse on September 18th, (9%) for the Americas, Europe and Africa.
-An annular eclipse on October 2nd for the southern tip of South America.
Don’t miss the final eclipse of 2023, either live or online.