THE WANDERING ASTRONOMER
Monday, October 2, 2023
The Other Eclipse
And the waiting continues.
The unbearably interminable interlude between the present moment and THE event: a slow, but inexorable passage of the moon across the Sun on April 8, 2024. In 193 days (or 4639 hours), the Greater of all great American eclipses - only two have been so designated*, including the one that has not yet occurred- will commence. While our sinews assume a harp-string tension, our respiration becomes increasingly more labored, our peripheral neurons spark off like pyrotechnics and we realize that the mindfulness tenant about living fully and exuberantly in every present moment while paying scant attention to the future is little more than a heaping handful of curdled codswallop, we shouldn't forget that another eclipse will occur later this month!
Saturday, October 14, 2023
to be precise.
As is true with every eclipse, what an observer sees depends on the observer's location. While those within the totality path will see an annular solar eclipse, other less fortunate sky watchers will be treated only to a partial eclipse, the magnitude of which decreases with increasing distance from the totality path. As we can see from the map below, the totality path begins in the north Pacific, slices across the western and southern United States before meandering across the Gulf of Mexico before gliding majestically over the Yucatan Peninsula , eastern Central and finally across the northern part of South America.
An annular solar eclipse occurs when the moon moves directly in front of the Sun when it is at or near apogee, its point of greatest distance. As the moon will be farther away than usual, its angular diameter (30' 5.8") will be smaller than that of the Sun (32'04"). Consequently, the moon will not obscure the entire solar disk. Instead, at 'totality,' the moon will appear as a dark circle surrounded by a ring of fire, Mr. Cash. The word 'annular eclipse' derives from the Latin word 'annulus' meaning ring.
This gorgeous image shows the Sun during an annular solar eclipse. Image credit: : Chayanan Phomsukwisit
Those outside the totality path will not see the ring effect. Instead, only a partial eclipse will be visible. As one can readily infer, during this type of eclipse the moon only blocks part of the Sun. And, one might ask, "Well, isn't that true of the annular eclipse, as well?" To which we reply, "This explains why lawyers should never write astronomy blogs."
We here in the Greater Portland area will only see a slightly partial eclipse because we're quite a substantial distance from the Totality Path. When the eclipse reaches maximum at 1:25 p.m. on Sat, Oct 14th, its magnitude will only be 0.262. Magnitude refers to the percentage of the Sun's diameter the moon blocks. This value is not the same as the obscuration percentage, which measures the percentage of the Sun's surface area the moon covers. At the magnitude of 0.262, about 17% of the Sun's face will be shielded by the moon.
The Time-Table specific for Portland is as follows:
12:21.00 p.m. Partial Eclipse begins
We first see the dark edge of the moon against the Sun
We first see the dark edge of the moon against the Sun
1:25.50 p.m. Maximum eclipse
The time when the moon covers the maximum amount of the Sun from our perspective
2:30.16 p.m. Eclipse ends
The moon is no longer seen against the Sun.
You can find the times relative to your location at the following web-site:
While this event won't be dazzling enough to sow superstitious terror amongst the intellectual elites, it does affirm the power inherent in that hurly-burly witchery of mathematical astronomy: humanity's ability to precisely predict the motions of grand celestial worlds. While we might not exert any influence over the empyreal realm, we can at least know how the celestial orbs interact.
Consider this a mere taste of the feast that awaits us in April.
*The first 'Great American Eclipse' occurred on August 21, 2017.