Dear Friend,
The entire staff of Lookout Observatory – that would be me – went to Farewell Bend State Recreation Area near the small town of Ontario, Oregon, to observe the recent total eclipse of the sun. Anitra and I joined 15 others for an eclipse expedition organized and led by my childhood friend, Dr. Fritz Kleinhans, a veteran of (I believe) 7 or 8 previous expeditions. We had perfect weather and a lovely, uncrowded view from a grassy hill of the sun rising over the Snake River.
A solar eclipse occurs when the moon in its monthly journey around the earth happens to come between the earth and the sun. The moon often goes a bit above or below the sun, but when it goes directly in front, it briefly blocks out the sun, and an eclipse occurs. Because the moon’s orbit is elliptical, not circular, it sometimes appears a bit smaller than the sun and it sometimes appears a bit larger that the sun. When it is smaller, an annular eclipse occurs, so called because it leaves a small ring of the bright sun still visible around the moon. When the moon appears larger, it can completely cover the sun, and a total eclipse occurs. As the moon moves in front of the sun, it appears to take larger and larger bites out of the sun, until only a very thin crescent is left. As this happens the sky turns to twilight and the air cools quite noticeably. Then rather suddenly the bright sun disappears entirely, protective glasses are no longer needed, and a black moon is surrounded by a soft, radiating glow of the sun’s outer atmosphere – the corona. It is very dramatic and awe-inspiring.
Many people across the U.S. Outside the path of totality were able to see the partial phases, so I will not include pictures of that, but only pictures of totality.
The first image is actually a few seconds before totality, when the last bit of the bright sun is still shining through one or more valleys at the moon’s edge, but the glow of the sun’s corona is starting to show around the black moon. This is called the diamond ring effect – for obvious reasons.
The second image was taken 8 seconds later, at precisely one second before 10:25 AM Pacific Daylight time. The moon, moving from left (west) to right (east) is now covering all but the last flickers of the the sun’s bright disk (the photoshpere), and the red (from burning hydrogen) of the chromosphere is visible along much of the right edge. Because this was a very short exposure (1/1000 second), only a faint glow of the inner corona shows surrounding the whole moon. If you magnify the right edge, you will see that parts of the thin white arc are actually broken up into small sections or “beads” of light. These so-called Baily’s beads were correctly explained by Francis Baily in 1836 as being caused by the irregular mountains and valleys along the edge of the silhouetted moon. Opposite, along the left edge, where the bright photoshpere is completely covered, and even the thin red chromosphere has not yet come into view, you can see just the tops of some prominences, large red arc-like eruptions from the sun that typically last a few days before falling back into the sun. Look at roughly the 8 o’clock and 10:30 positions.
The third image, taken 16 seconds later, was a longer 1/100-second exposure, so it well shows the inner corona, the thin, extremely hot gas-like plasma material surrounding the sun that extends far into space. The irregular shape and the pattern of streaks are caused by the sun’s strong magnetic field. Without highly specialized scientific equipment designed within the past century, the only time the sun’s corona is visible is during a total solar eclipse. It is this unique view of the sun that is so startling and majestic during an eclipse. If you look closely at the 8 o’clock and 10:30 positions, you will see the two red prominences whose tops only were visible in the previous image.
The fourth image, a 1/800-second exposure taken 1 minute and 33 seconds later, shows that by now the moon has moved far enough along to expose the red chromosphere on the western side of the sun. An additional prominence at about 7 o’clock is now visible. The largest prominence (near 8 o’clock) is very modest as prominences go, yet it extends more than 3 earth diameters away from the sun. The earth would easily fit into the dark space under its looping arc!
Fifteen seconds later totality had ended, the partial phases resumed in reverse order, and the majesty and wonder was just a memory – except partly captured forever in images.
Still in awe,
Carter, (sometime) Resident Astronomer,
Lookout Observatory
