Montana News

May 20, 2012 3:21 PM by Mike Heard (Bozeman)

Partial solar eclipse may be visible in Montana on Sunday

A partial solar eclipse may be visible over Montana and Idaho on Sunday, May 20th beginning at 6:14pm (Montana time) and ending at around 8:20 pm.

At its peak - around 7:20 pm - about 71% of the setting sun will be occulted by the rising moon.

This is the first time in 10 years an eclipse will be visible over Montana.

(From the NASA Eclipse Website) On May 20-21, 2012, an annular eclipse of the Sun is visible from within a narrow corridor that traverses Earth's northern Hemisphere. The path of the Moon's antumbral shadow begins in eastern Asia and crosses the North Pacific Ocean where it ends in the western United States.

The eclipse will be visible from a 240 to 300 kilometre-wide track that traverses eastern Asia, the northern Pacific Ocean and the western United States. A partial eclipse will be visible within the much broader path of the Moon's penumbral shadow, that includes much of Asia, the Pacific and the western 2/3 of North America.

The shadow passes just south of Alaska's Aleutian Islands as the central track slowly curves to the southeast. After a 7000 kilometre-long ocean voyage lasting nearly 2 hours, the antumbra finally reaches land again along the rugged coastlines of southern Oregon and northern California (Figure 2) at 01:23 UT (May 20 local time).

Redding, CA lies 30 kilometres south of the central line. Nevertheless, it still experiences an annular phase lasting 4 1/2 minutes beginning at 01:26 UT. It is already late afternoon along this section of the eclipse path. Central Nevada, southern Utah, and northern Arizona are all within the annular path.

By the time the antumbra reaches Albuquerque, NM (01:34 UT), the central duration is still 4 1/2 minutes, but the Sun's altitude has dropped to 5°. As its leading edge reaches the Texas Panhandle, the shadow is now an elongated ellipse extending all the way to Nevada. Seconds later, the antumbra begins its rise back into space above western Texas as the track and the annular eclipse end.

During the course of its 3.5-hour trajectory, the antumbra's track is approximately 13,600 kilometres long and covers 0.74% of Earth's surface area.

Partial phases of the eclipse are visible primarily from the USA, Canada, the Pacific and East Asia.

For more information on solar and lunar eclipses, see Fred Espenak's Eclipse Web Site at


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