The Celestial Sphere

By Matthew Johnson
During the month of April there are events which will capture and hold the interest and minds of both
professional scientists and Americans of all ages.

On April 8, 2024, a total solar eclipse will cross North America, passing over parts of Mexico, the United
States and Canada. A total solar eclipse occurs when the sun, moon and Earth line up exactly, with the
moon positioned between the sun and Earth and near enough to both so that the moon’s shadow
completely covers the sun, and this shadow also reaches the earth.

The shadow of the moon upon the earth has two divisions: an outer, lighter area called the penumbra
and the inner, darker area called the shadow’s umbra. Those viewing under the umbra will view a total
eclipse, and those observing under the penumbra’s shadow will witness a partial eclipse of the sun.
Citizens of Norfolk who wish to view the total eclipse while doing their best to stay close to home,
maintaining economies of time and expense, must travel north toward the path of totality. Examples of
such destinations are areas within 20 or so miles either north or south of Plattsburg, N.Y., Burlington,
Vt., and Caribou, Me. Anyone viewing the eclipse farther than 20 miles south or north of the narrow
path of totality will witness only a partial eclipse of the sun.

Viewed from Norfolk, 92 percent of the sun will be eclipsed by the moon. This may sound like there will
be a great darkening of the sky—92 percent is quite close to 100 percent—but this is less of a change
than it seems. Partial eclipses are virtually unnoticeable in terms of the sun’s brightness. It takes well
over 90 percent coverage to notice any darkening at all. Even at 99 percent, it would be not much darker
than twilight. This is because the human eye quickly accommodates to darkness, with the pupil of the
eye widening to let in more light. Additionally, there is a slow buildup of visual purple in the eye, a
chemical that assists in night vision.

When viewing a solar eclipse, safety is the priority. Everyone should be familiar with the need to wear or
use specialized eye protection designed for safe solar viewing. Viewing any part of the bright sun
through a camera, telescope or binoculars without a special-purpose filter will cause severe eye injury.
Except during the few minutes of totality, when the moon completely blocks the sun’s bright face, it is
never safe to look directly at the sun without proper filtering. When observing the partial phases of the
eclipse, one must also use solar viewing glasses, a handheld solar viewer or employ an indirect method,
such as a pinhole projector. Eyewear approved for direct viewing of the sun during an eclipse is widely
available and inexpensive. Solar glasses are even available in many gas stations.

A total eclipse can be an emotional experience. If one has not witnessed a total eclipse, it is distant from
what one has experienced in life. When totality occurs, one will experience the blackest black—where
the moon covers the sun—surrounded by the ethereal beauty of the sun’s corona (its outer
atmosphere) and a possible panoply of colors that the atmosphere sometimes takes on. As the moon’s
shadow approaches, the sky will change from daylight to deep twilight, and planets and stars will begin
to appear.

Using Burlington, Vt., as a potential viewing site of the eclipse, the following data is exact. The partial
eclipse, or the beginning of the moon blocking the sun, is termed first contact. This will occur at 2:14
p.m. EDT. Totality will begin one hour and 12 seconds later, at 3:26 p.m., and will last three minutes and
14 seconds. The sun will then begin to reappear, and the eclipse will end at 4:37 p.m. The entire eclipse
event will last two hours and 23 seconds.

Now comes a description of what one will view in the sky in the background of the eclipse, as if one
were viewing the eclipse from anywhere between Rochester, N.Y., and Caribou, Me.

The sun will be approximately 45 degrees high in the southwest and lie within the zodiacal constellation
of Pisces. This constellation is composed of mostly faint stars, and the other constellations surrounding
it are composed mostly of stars that are equally faint. This is fortunate, as during totality, five planets
are in the proximity of the sun, with two definitely visible before, during and after totality. The planet
Venus will be 15 degrees west-southwest of the eclipsed sun. Since it is the third brightest object in the
sky (after the moon and sun), it will be visible for 15 minutes before and after totality.

Once again, viewers should be exceptionally cautious, since they would not usually use a sun filter to
view the planets at this time. Those using binoculars to view the planets should be especially careful to
not sweep the partially eclipsed sun into the field of view, as eye damage will certainly occur that could
be permanent. When viewing objects near the sun, it is best to locate oneself beside something, like the
side of a building or a car, that can keep the sun hidden from view. Best advice: unless one is a
consummate eclipse viewer and imager, one should refrain from any such activity unless using proper
solar filtering, to protect delicate retinal tissues.

Jupiter can be found 30 degrees east-northeast of the sun. Since Jupiter is five times dimmer than
Venus, it can be viewed only during totality. Totality lasts only three to four minutes, so one should only
spend a few seconds locating the planets; if any difficulties arise, be sure to return to view the sun at
totality.

On April 8, the day of the eclipse, Aton Forest, together with board member Matthew Johnson, will be
hosting an eclipse observation in Norfolk. Interested participants should check with the Norfolk Hub for
the location and time.