Thursday, May 12, 2016

There's A Little Black Dot on the Sun Today ...

Well several.

Including a very round one. Mercury.  The others are sunspots.

On Monday May 9, 2016, Mercury transited the Sun. While not as rare as transits of Venus, Mercury transits are not everyday occurrences. The last one was in 2006. The next are in 2019 and then 2032. Luckily for us, the entire transit would be visible here and Monday was the first day in a week for which the forecast did not call for rain.

And thus we got to see it.

Well most of it.

In the image above, Mercury is just to the left of the vertical center line and in the bottom half of the Sun's disk. Below, Mercury is just right and under center.

You can easily see that Mercury has moved across the face of the sun.

In the above shot you can see Mercury just entering the disk of the sun at about the 7:30 position or 225° from the top (the image is not quite in focus and was shot through thin clouds). As always, click on the image to bigafy it.

Below is the setup at our observing site. My setup is closest and was the simplest, it took me a half hour to get ready. First contact was at 7:12 am local time. I arrived around 6:40 am, cutting it close. The other guys got there around 5:00 am, as they needed to align their mounts and setup fancier telescopes. Of course, they had the benefit of tracking the sun across the sky, while I had to keep manually moving my optics (one of the reasons the sun isn't the same location in each image).

The other two observers are both under cover as they try to focus, a non-trivial endeavor made worse by the small image size of features on the sun and the bright ambient daylight (think viewing your phone in bright sunshine).

Alas, we did not get to observe the entire event. At just about the halfway point clouds rolled in and the show was over. We waited a bit in hopes of sucker holes but our luck had run out.

Overall it was an enjoyable morning, surprisingly relaxing compared to other solar events such as eclipses and ISS transits, in no small part due to the differences in duration. And yet it was still over much too soon.

Next up, a total solar eclipse that will cross the continental US in August 2017. I suspect our observing site will be much more crowded for that event.

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