Aug 10, 1999

Don't Forget the Partial Eclipse!





The maritime provinces of Canada and the east coast of the USA could experience interesting shadow effects from the partial eclipse near sunrise.
partial eclipse map, copyright Sky & Telescope
August 10, 1999: This week's total eclipse won't be visible from North America, although it's a close call. The darkest part of the Moon's shadow, called the "umbra", touches down on Wednesday morning at 5:30 a.m. EDT about 430 miles east of New York City. In the western Atlantic, totality will last a mere 47 seconds as the path of totality races eastward across the ocean toward its first landfall in England.

Right: This image created by Sky & Telescope magazine shows the details of the partial eclipse in North America on August 11, 1999. Copyright: Sky & Telescope. All rights reserved. to view a larger image.


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Although eclipse-lovers in North America will miss the experience of totality, there will still be a partial eclipse visible in parts of Canada and in the United States as far south as North carolina. Observers in the maritime provinces of Canada will witness almost total coverage of the Sun, while in New York skywatchers can expect 46% coverage just as the sun is rising over the Eastern horizon.

In places like New York where a large fraction of the Sun will be occulted by the Moon just before sunrise, the eclipse could have an effect on the morning twilight. The sky could look especially strange if any thin cirrus is present along the eastern horizon. The possibility of unusual lighting around sunrise is explored further in a Sky & Telescope article "The Eclipse Outside Totality" by Joe Rao.
Partial Eclipse Predictions for US Cities
image courtesy of the Society
for Popular Astronomy
While a partial solar eclipse is not nearly so dramatic as a total eclipse, it is still worth observing. The primary consideration when viewing the Sun should always be eye safety. Serious eye damage can result from a brief glimpse of the Sun, even when it is almost completely obscured by the Moon. One safe way to observe a partial eclipse is by projecting the image of the sun through a telescope or binoculars onto a white screen, a paper plate, or some other surface. In the case of a telescope, make sure that any small finder telescope is capped, and keep the cover on one half of the binoculars. Be sure not to look through the telescope to point it at the Sun -- partial or total blindness will almost surely result.

On the screen you should see a bright circle of light, which will probably be blurred. Focus the instrument until the circle is sharp. This is the disc of the Sun itself. If the eclipse is in progress you should see the Moon as a dark bite out of one edge. Using this method it is also possible to see considerable detail in and around sunspot groups. Pinhole projectors and certain types of solar filters also provide a means of watching a partial eclipse safely.
visit Thursday's Classroom
Please visit
Thursday's Classroom
for lesson plans and activities related to the August 11, 1999 total solar eclipse.
Right: It's possible to project a faint image of the Sun through a simple pinhole. Take two pieces of stiff paper or cardboard (paper plates work well) and use a pin to make a hole about 1 mm across in one of them. One piece is the screen and one is the pinhole projector. Hold your screen about 6 inches behind the projector (the one with the hole) and you should see a small image of the Sun on it. Again, the farther away it is the larger and fainter it becomes. Image courtesy The Society for Popular Astronomy.

For more information about the August 11, 1999 solar eclipse, please see Goddard Space Flight Center's Solar Eclipse home page. Also, please visit Science@NASA's for sights, sounds, and science news from the August 11 total eclipse.


Web Links
For lesson plans and educational activities about the August 11th eclipse, see Thursday's Classroom.


Decrypting the Eclipse - August 6, 1999, scientsts around the world explore the possible and mysterious effect of eclipses on the motion of Foucault's pendulum.


There goes the Sun - August 5, 1999, features general information about the August 11, 1999 solar eclipse, including the effect of eclipses on the birds and the bees, and eclipses on other planets.


Audio eclipse may fill the sky - August 4, 1999 story on investigations of ionization and radio propagation in Earth's atmosphere during the eclipse

Peering through a Hole in the Sky - June 17, 1999 story on exotic gravity measurements to be carried out during the eclipse


Partial Eclipse predictions for North America - from Sky & Telescope


Worldwide Partial Eclipse predictions - from Sky & Telescope

The Millennium's Last Solar Eclipse -- from Sky &Telescope

Solar Eclipse Home Page -- at the NASA/Goddard Space Flight Center


Total Eclipses of the Sun, J.B. Zirker, 1995, Princeton University Press

The Sun in Eclipse, Michael Maunder and Patrick Moore, 1998, Springer-Verlag

Totality: Eclipses of the Sun, Mark Littmann, Ken Willcox and Fred Espanek, 1999, Oxford University Press

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For more information, please contact:
Dr. John M. Horack , Director of Science Communications
Author: Dr. Tony Phillips
Curator: Bryan Walls
NASA Official: John M. Horack