THE SOUTHWORTH PLANETARIUM
University of Southern Maine
70 Falmouth Street
Portland, Maine 04103
THE SOUTHWORTH ASTRONOMER
Saturday, March 23, 2024
Up, Down and Around the Totality Path
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*16 DAYS UNTIL THE TOTAL SOLAR ECLIPSE!*
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The upcoming April 8th celestial rave has been dubbed the "Second Great
> American Eclipse," the first having occurred on August 21, 2017. Both
> events have been infused with this sense of nationalistic fervour because
> during both eclipses almost everyone within the continential United
> States was (2017) or will be (2024) able to observe at least a partial
> eclipse, if not a total one. That fact should assuage some of the anguish
> that is currently tormenting those unable to travel to the totality path,
> the sinuous band within which one is only able to observe totality.
> Even if you are not observing within the totality path, you'll still see
> "something."
During the last few months, many people have asked, "Since we're in
Portland, we won't see the eclipse, will we?" While it is true that
Portlanders won't see the total eclipse, the moon will still block most of
the Sun (95%) at maximum. This obscuration value is so high because
Portland is relatively close to the totality path. The obscuration
percentage will diminish with increasing distance from this path. Please
refer to the image below.
[image: 8jWBfwmeBt9okPmbJEpWHF-1200-80.png]
Observe that even observers in the extreme Pacific Northwest can watch the
moon blocking between 10-10% of the Sun at maximum eclipse. Key West sky
watchers will see 40 -50% of the Sun blocked at maximum. As is
true with all things astronomical, it's all about location, location and
location. Everyone within the continental United States will see at least
a partial eclipse.
Within the totality path, itself, one will also see variations, not in
magnitude or obscuration, but in duration: how long totality will last.
Here again, location is the key. The closer an observer moves toward
the central line, the longer the totality duration will be. The below
graphic shows the totality durations for various cities within the totality
path. We can see that Dallas observers will enjoy 3 minutes, 51 seconds
of totality, whereas Austin observers will have to be content with only 1
minute and 44 seconds.
To understand why the durations are so different, one must envision the
moon's shadow as a dark circle traveling across the path. A point
toward the center part of the circle will remain within the shadow far
longer than a point located toward its edge.
[image: map_usa_2024_durations.png]
This traveling shadow circle will describe the entire totality path, which
begins in the South Pacific. The path will first touch land around
Matazlan, Mexico at 11:07 a.m. MT. The path will then cross the
Mexico/USA border* at 12:27 p.m. Central time (1:27 p.m. Eastern).
After passing through the eastern United States, the moon's shadow first
crosses the Canadian border at 3:12 p.m. and straddles the border. It
enters Maine at 3:28 p.m. ET and leaves at 3;35 p.m. The shadow then
travels through New Brunswick, Quebec, over Prince Edward Island and
reaches Newfoundland at 5:09 p.m. NT (Newfoundland Time = 3:39 p.m. ET)**
The shadow exits Newfoundland around Gander at 5:16 p.m. NT (3:46 p.m.
ET).
The totality path then ends in the North Atlantic.
Due to the path's location and the widespread pre-event publicity, this
eclipse might well be the most watched total solar eclipse in world
history. While slightly more than thirty million people live within the
totality path, the number of observers could well exceed fifty million!
Perhaps "The Second Great American Eclipse" is a sensible sobriquet after
all.
Next: What About the Lunar Eclipse?
*If you think I'm going to make any smart remarks about this, you're crazy.
**In order to compensate Newfoundlanders for having their province's name
mispronounced by the entire English-speaking world, they were given their
own time-zone, which is 1.5 hours ahead of Eastern Time.