The Transit of Venus from Winona, Minnesota

.....I was a bit jealous of a friend of mine who lives in Japan, and who would therefore have the Sun above the horizon for the entire time that Venus was transiting the Sun, only to find out that he barely got to see any of it, due to clouds.  We were much luckier in Minnesota.  The sky was clear for all of the transit, from the first kiss of Venus on the Sun until sunset, about three and a half hours later.

And there were ducklings.  Ducklings are cool.

.....My setup point was on the eastern side of Lake Winona, where we had an excellent view of the western horizon.  I didn't really advertise this fact with any real lead time, so this location let me attract interest from really quite a lot of people walking around the vicinity.  (I must specifically thank Tony Thelen, who had come to see the transit and did a lot to invite/collect/waylay passers-by to take a look.)

Trying to center the Sun

.....Solar observing adds complications, because if you do the wrong thing, you do nigh-instantaneous long-term damage to your eye.  There were two safe observing methods that I used for this event.  On the front of the telescope, I have a solar filter that blocks out the vast majority of the light, especially ultraviolet light.  Since I don't have a solar filter for my finderscope, and I seriously doubt that one exists, I try to get the Sun in view by making the shadow of the telescope as small as possible.  Even then, I usually need to take a few seconds "wandering around" in the sky.  

.....The Sun against the sky in not really a very large target, it only covers an area of the sky about one-half of one degree.  You could fit 360 Suns, side-to-side, across the sky from horizon to horizon.  Hold out at dime at arm's length, and you will easily cover the Sun.  In a telescope with a solar filter, the Sun appears as a bright yellow disk of light, and nothing else is even bright enough to show up.

And hanging out with the ducklings

.....I had done this part many, many times before, so all that was left was waiting for Venus to appear at the edge of the Sun.






.....Venus is closer to the Sun than the Earth; this is why Venus can be seen passing in front of the Sun.  It also means that we never see all of Venus against the sky.  When Venus is visible in the morning or evening sky, it is brighter than anything besides the Sun and the Moon, but seen through a telescope, Venus shows phases like the Moon.  Half of Venus is always lit, half of Venus always faces the Earth, but these can't be the same halves while Venus is visible, as shown below.

 

.....In fact, the only time we can see the full disk of Venus is when we cannot see Venus at all, when Venus transits the Sun.  What we see is the silhouette of Venus blocking the light of the Sun.  The dark marks on the Sun that are not the shadow of the planet Venus are sunspots, places where the Sun's magnetic field has been gnarled such that the magnetic field lines spring out from the surface, trapping gas at these kinks.  This gas isn't able to get replaced by new hot gas bubbling up from below, so it cools to a mere 7500 Fahrenheit, as opposed to the 10,000 Fahrenheit of the rest of the Sun's surface and appears dark against the much hotter surface.

.....When looking at something in a telescope, the image moves across the field of view due to the rotation of the Earth.  (Or, as it appears against the sky, celestial objects rising and setting.)  In this case, watching Venus move across the Sun is actually watching Venus moving in its orbit.  You can watch real change happening!  I think that this is one of the appeals in this type of astronomy.  The idea of the ancients that the heavens were eternal and changeless is still a pretty good day-to-day guide.  The Sun Moon, and planets make patterns, but something like this (that happened last in 1882, and then 2004, and the next one will be in 2117) lets us in to get a opportunity to mark one moment as separate and unique, to share with everyone else watching just at that moment.
 

.....Many ephemeral astronomical events are actually dependent on where you happen to be standing.  If you see a meteor, you share that with everyone else in a hundred miles or so, as that is small matter heating up in the Earth's atmosphere.  In a solar eclipse, such as the annular eclipse two weeks back (not well set up for most of the continental United States) the path of the eclipse is moving across the surface of the Earth, so where you are matters.  For this case, everything was happening 30 million miles away, so if you got to see it, you shared that moment with every other person on Earth watching at that time.

Speaking of these events ...

 .....The next solar eclipse will be on November 13th, but unless I have an audience in northernmost Queensland, you won't get to see totality. Northern Australia also gets an annular eclipse on May 9th.  North America gets a really good solar eclipse on August 21st, 2017, but I have plenty of time to write about that.  The next lunar eclipse for North America will be on April 15th, 2014. 

.....Happily, (with special thanks to my wife, and to Anthony Thelen, who are apparently much more accessible to people than I am when say "Hey, come look at the Sun!") a good time was had by all.

 

Photos by author (Sun, sunset), and Anne Marie Leckenby everything else.