SKY WATCHING

 If you decide to experience the total eclipse ...

As for totality itself, observers expecting to see it can enhance the view by dark-adapting their eyes during the preceding partial phases. Dark glasses will help, but better adaptation can be achieved by wearing a patch over one eye and removing it only after the sun's disk is completely covered by the moon. Also very effective are surplus red adaptation goggles used for military purposes during World War II. 
Since the surface brightness of the solar corona is about equal to that of the full moon, during totality no filters are necessary for either naked-eye or telescopic viewing. But care should be taken to avoid exposure in direct sunlight when it returns (often as the diamond-ring effect) at the end of totality. 

Joe Rao serves as an instructor and guest lecturer at New York's Hayden Planetarium. He writes about astronomy for Natural History magazine, the Farmers' Almanac and other publications. 

Total solar eclipse April 8, 2024: What you'll see if you're outside the path of totality

News

By Joe Rao

 published about 7 hours ago

Unlike a total eclipse of the sun, concentrating its excitement into a few fleeting minutes, a partial eclipse can be watched leisurely from wherever one happens to be.

Total solar eclipse April 8, 2024: What you'll see if you're outside the path of totality

A map of the United States showing the path of totality and degrees of partiality during the solar eclipse on April 8, 2024. (Image credit: Larry Koehn/ShadowAndSubstance.com)

Mark Monday, April 8, 2024, on your calendar as "Solar Eclipse Day," for if the weather is fair, you should have no difficulty observing a partial eclipse of the sun from much of North America. This celestial event will be associated with a spectacular total eclipse in a narrow zone of the southern and eastern United States, in which the moon completely blocks out the disk of the sun. Truly, a "bucket list" event!

Meanwhile, viewers about 2,600 miles (4,200 km) on either side of the totality path will get a partial eclipse, with the moon initially making a slight dent in the sun's edge. The dent is the silhouette of the moon's limb, and in a properly filtered telescope, lunar mountains can be seen to roughen its curve. As the minutes pass, the dent slowly grows and deepens to turn the sun into a crescent. In a partial eclipse, the indentation appears to swing around the sun's limb, moving roughly from west to east. 

Unlike a total eclipse of the sun, concentrating its excitement into a few fleeting minutes, a partial eclipse can be watched leisurely from wherever one happens to be.

Related: Total solar eclipse 2024: Everything you need to know
Read more: Total solar eclipse April 8, 2024: The longest and most visible for the US in 100 years

During the eclipse, drawings and photographs can be made to show the moon's progress across the solar disk. The moon may temporarily hide sunspots. Observers with small telescopes can try to time the first and last instants when the moon's disk is visible against that of the disk of the sun. 

Timings of precisely when the edge of the moon first touches or last leaves the sun's disk are less sharply defined than the beginning and end of a total solar eclipse, but are nevertheless useful. An arctic explorer of 150 years ago might have carefully timed these events for the chance of getting a reasonably good fix on the geographic longitude, after months of rugged dog sledding when a chronometer could no longer be trusted to provide Greenwich time. By observing the annular eclipse of Aug. 5, 1766, the famous navigator Capt. James Cook found for the longitude of an island off the coast of Newfoundland; a value that differs from the modern value by only 22 arc seconds.

TABLE OF EVENTS

The table below provides local circumstances for 20 cities and provides the times for the beginning and end of the eclipse as well as the time of the maximum phase of the eclipse. The magnitude is defined as the fraction of the sun's diameter covered by the moon. Thus, for Chicago, Illinois, as much as 94.2% of the sun's diameter will be covered during early afternoon. In Honolulu, the greatest eclipse amounts to 28.6% less than an hour after sunrise. 
When interpolating for a site between two cities, convert the times to the same time zone if they are not already. 

Local circumstances of the partial solar eclipse on April 8, 2024

Location	Time zone	Eclipse starts	Maximum	Magnitude	Eclipse ends
Atlanta, GA	EDT	1:45 PM	3:04 PM	0.846	4:20 PM
Boston, MA	EDT	2:16 PM	3:29 PM	0.931	4:39 PM
Chicago, IL	CDT	12:51 PM	2:07 PM	0.942	3:21 PM
Cincinnati, OH	EDT	1:52 PM	3:09 PM	0.993	4:24 PM
Denver, CO	MDT	11:28 AM	12:40 PM	0.715	1:53 PM
Helena, MT	MDT	11:38 AM	12:40 PM	0.474	1:42 PM
Honolulu, HI	HST	6:33 AM	7:12 AM	0.286	7:54 AM
Houston, TX	CDT	12:19 PM	1:40 PM	0.943	3:01 PM
Juneau, AK	AKDT	10:10 AM	10:33 AM	0.064	10:56 AM
Los Angeles. CA	PDT	10:06 AM	11:12 AM	0.58	12:22 PM
Miami. FL	EDT	1:47 PM	3:01 PM	0.556	4:13 PM
Monterrey, MX	CST	11:04 AM	12:24 PM	0.953	1:46 PM
New Orleans, LA	CDT	12:29 PM	1:49 PM	0.844	3:08 PM
New York, NY	EDT	2:10 PM	3:25 PM	0.91	4:36 PM
Seattle, WA	PDT	10:38 AM	11:29 AM	0.311	12:21 PM
St. Louis, MO	CDT	12:42 PM	2:00 PM	0.988	3:17 PM
Toronto, ON	EDT	2:04 PM	3:19 PM	0.999	4:31 PM
Tucson, AZ	MST	10:06 AM	11:19 AM	0.749	12:36 PM
Washington, DC	EDT	2:04 PM	3:20 PM	0.89	4:32 PM
Winnipeg, MB	CDT	12:54 PM	2:01 PM	0.62	3:08 PM

The closer an observer is to the path of totality, the larger the percentage of the sun's diameter that will be covered by the moon at greatest eclipse. As the table shows, the eclipse is practically total at Cincinnati (magnitude 0.993), but at Juneau the moon will reach only about one-sixteenth of a way across the solar disk (magnitude 0.064). At these two cities, maximum eclipse will occur at 3:09 p.m. Eastern Daylight Time and at 10:33 a.m. Alaska Daylight Time, respectively. 

Of the cities listed in the table, Juneau will have the shortest eclipse duration, just 46 minutes. The longest eclipse will occur at Monterrey and Houston, two hours, 42 minutes.

Across the western half of the continent, mid-eclipse will occur during the late-morning or midday, while farther east the phenomenon will take place during early-to-mid afternoon, high in the south-southwest sky. 

Check out this fascinating animation of how the moon will appear to eclipse the sun across North America, courtesy of Larry Koehn of https://www.shadowandsubstance.com/ 

Eclipse effects 

Many ancient peoples were terrified by the sun's misshapen appearance in a partial eclipse, believing that the sun was diseased, under attack or foretelling woe to its watchers. 
If, for your area, the sun becomes at least 80 percent eclipsed, it will have the shape of an elongated crescent. Sunlight will then be coming only from the sun's redder limb regions; overall illumination on the ground will trend toward dusky. If you are within 110 miles (175 km) of the totality path, the moon will obscure 95 percent or more of the disk of the sun. The crescent sun will then shine with only 1/10 of the sun's normal total light, but this is less than a change than it sounds, since our eyes adapt readily to changing light levels. 
The illumination will be no darker than on a bright overcast day. The quality of the light, however, may become unearthly. A clear sky should turn an abnormally deep blue and purer; the landscape transforms to a slightly alien, silvery or metallic look, about like that of a clear day on the planet Mars. The temperature may drop perceptibly, and chill breezes might also begin to blow. 
Venus, shining at magnitude -3.9, should become easily visible 15 degrees to the lower right of the sun. Block the sun with your hand to search for it. Even Jupiter, fainter at magnitude -2.0, may be detectable 30 degrees to the sun's upper left if the air is very clear.