There has been an interesting and unusual coincidence of solar system machinations here within the last 16 days. On May 20, we were able to witness a partial annular solar eclipse, which was followed by a partial lunar eclipse on June 4, and finally, today we were able to observe the transit of Venus across the Sun. Fortunately, we have frequent clear weather, so we were able to watch the best two of the three events.
Partial Annular Solar Eclipse:
May 20: we were having family visit for dinner when the eclipse occurred, around 7:00 p.m., and I had not done anything to prepare to take photographs. The pin-hole camera I cobbled together with a corrugated cardboard box worked fairly well, but the small and slightly diffuse image it projected onto a sheet of vellum was a bit unsatisfying, so we gave that up to just watch.
The Moon appeared to small to cover the Sun completely, and since we were not in the most opportune location for viewing, the Moon would not cross the center of the Sun, and at its maximum would just produce a sharply-pointed crescent. Even in a total eclipse, the sun is too bright to look at directly, so we resorted to other methods. I remembered that dense trees could act to focus images on the ground as light passed through small apertures formed by spaces between leaves in the canopies, so we looked around and were able to find little crescent-shaped images everywhere.
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| Roughly crescent-shaped dappled sun on the back of the house |
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| This shadow was formed by a small tree with a fairly open canopy, but the repeated crescents are clearly visible. |
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| Much better definition in this shadow, taken near the maximum of the eclipse. |
Since I did not have any suitable filters or welding glasses, I pinched the aperture down as tight as it would go, and pushed the shutter speed to 1/5000, and pointed at the sun and hoped for the best. The sun is still obviously too bright to resolve properly, but it is obviously not round; the lens flares provide dimmer (reversed) reflections that show the shape of the eclipse:
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| Lens flares are shaped like the eclipse, and appear backwards. |
As the Moon crossed the Sun, it darkened quickly and
cooled
noticeably. The quality of light during the eclipse was striking -
although it was becoming dimmer, shadows remained sharp and distinct in
the low light. After a little while, the wind increased and shifted, as
it normally does here after sunset. The cats seemed to notice that
something wasn't quite right, but just settled into their usual twilight
routines.
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| Twilight is normally the time to poke in the bushes and chase bugs. |
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| Black Cat During Eclipse |
Lunar Eclipse:
Last night, June 4, there was a partial lunar eclipse that would have been visible here, but unfortunately, the regular spring weather pattern of nightly overcast prevailed. The marine layer of clouds forms just after sunset and usually lingers until late morning, so we were unable to watch.
Transit of Venus:
Today, June 5, the third event occurred; a transit of Venus across the Sun. This is a rare event: there will not be another one observable from Earth until 2117, so I did not want to miss this one.
The NASA website,
Astronomy Picture of the Day, provided satellite photos from the Solar Dynamics Observatory, which were updated every 15 minutes or so, and we began watching the transit start around 3:00 p.m. (Pacific Time) at my office.
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| Image:
NASA/SDO
& the AIA, EVE, and HMI teams
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We built a a couple of pin-hole cameras, one from a long cardboard box, and another from some 3" cardboard tubes, but again, we were disappointed, as the small images were not sharp or bright enough to observe the spot of Venus against the sun.
I got home around 6:30, and the transit was only half over, so I tried a more optical approach. A pair of binoculars pointed at the Sun worked nicely to focus an image on paper:
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| Do it like this |
When doing this, find something to steady the binoculars or
telescope; it's a very touchy thing to hold the image in one spot, as
well as adjusting focus. Next time, I will use a tripod.
This produced a sufficiently large and sharp image to see the spot of Venus easily, and there are also a few sunspots barely visible within the circle of the Sun. (In retrospect, this would have been the thing to do with the partial
annular eclipse two weeks ago, but I had not thought far enough ahead
for that one.)
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| Venus is the spot on the right side of the disk. Fainter, diffuse points are sunspots. |
The eclipse on May 20 was the most complete I have seen so far, but I have to wait in order to cross off "Total Eclipse" from the "Things to Do" list. In August 2017, a total eclipse will be visible across the United States along a line from Oregon to South Carolina, so we plan on traveling somewhere to catch that when it happens.
