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October 25, 2014

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Venus puts on a show - and here's proof

On Tuesday skywatchers witnessed a rare planetary spectacle, as the planet Venus appeared to cross the face of the sun. If you missed it, you're out of luck. This once-in-a-lifetime event won't happen again until 2117.

But, even if you missed it, Mike Edmiston saved the day. He took some telescopes and binoculars out to Tom and Sue Schaaf's house to view the transit of Venus across the sun. Click here for Mike's photos.

Here's an explanation from Mike about the photos and the event:

The ordering of the inner planets in our Solar system (going outward from the sun) is Mercury, Venus, Earth, and Mars. This means Mercury and Venus can sometimes pass between Earth and the Sun, but Mars and the rest of the outer planets cannot pass between Earth and the Sun.

When either of Mercury or Venus passes between Earth and the sun it will appear as a "black dot" moving across the Sun. This is called a "transit" of the planet across the Sun. If the solar system were perfectly flat, transits of Mercury and Venus would happen frequently, but the orbits of the planets are slightly tilted with respect to each other. The tilt is sufficient that Mercury transits the Sun occasionally, and Venus transits the Sun rarely.

The Venus transits occur in June or December at intervals exhibiting an interesting repeating pattern of 8 years, 105.5 years, 8 years, 121.5 years, 8 years, 105.5 years, 8 years, 121.5 years, etc.

We had a transit of Venus in June 2004, and now a transit in June 2012. The next one will occur 105.5 years from now in December of 2117. Therefore, if you missed the 2004 and 2012 transits, you need to live another 105.5 years for the next one, and you need to move to Europe because the 2117 transit will occur at nighttime in Ohio.

Mercury transits occur in May or November with the May transits either 13 or 33 years apart, and the November transits occur 7 or 13 or 33 years apart. The next mercury transit occurs on May 9, 2016. It will be visible from Ohio if the weather cooperates.

Viewing the transits

The sun is so bright that you need eye protection to view a transit of Venus or Mercury. Ordinary sunglasses are not even close to sufficient protection, so never look at the sun with ordinary "sunglasses."

You need something more like a welder's mask to view the sun safely. But a welder's mask alone is insufficient to see Mercury, and barely sufficient to see Venus, because the black dots you are looking for are small. You need some magnification in addition to the darkening.

You need binoculars or telescopes that have been modified with special filters to block out 99.99% of the Sun's light, and you need magnification somewhere in the range of 10X (binoculars) to 50X (telescope).

The telescope and camera used to take the pictures

I used a 5-inch diameter telescope with magnification of 50 to view the 2012 transit of Venus. The telescope lens was covered with a special solar filter that blocks out 99.99% of the Sun's light. With the filter in place you can safely look into the eyepiece in the usual manner and view the magnified Sun.

This magnification is easily sufficient to see Venus (or Mercury) as well as "sunspots" if any sunspots are occurring. We are currently experiencing a peak number of sunspots, so photographs taken through the telescope on June 5, 2012 show sunspots as well as Venus.

It is possible to take reasonably good photographs through a telescope using a modern digital, automatic-focusing, point-and-shoot camera. The most difficult part is holding the camera steady at the correct position next to the telescope eyepiece.

I held a Nikon S8100 camera up to the telescope eyepiece to take my photos. A digital camera is much better than film because you know right away if you were successful or not.

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