Transit of Mercury

Clouds Limit Observation

Mercury passed in front of the Sun on November 11th. It was probably the last transit I'll observe in my lifetime. There will be Mercury transits in 2032 and 2039, but these will not be visible from Virginia. The next transit visible from Virginia will be on May 7, 2049.

I got up early to have all my equipment ready when the transit was predicted to start at 7:35 am. The temperature near sunrise was about 47 degrees, and there was no wind. Unfortunately, the sky was nearly covered by a combination of contrails and thin clouds as you can see in the satellite picture below. My observing location is marked with a small red dot. 

Clouds weren't thick enough to entirely block the Sun, but they made imaging difficult. In spite of my best efforts I missed the moment of ingress. By the time I was ready to capture images, it was 7:40 am. No matter, the seeing was absolutely terrible. Although Mercury's black disc was visible near the solar limb on my laptop monitor, its warped, contorting shape was swimming around. The limb looked like a waving rope. No amount of image processing would remove these blurry distortions.

Atmospheric steadiness increased gradually as morning progressed. I continued capturing video clips hoping one of them would catch a few cloud free moments. At 9:05 am I recorded a cloudless 400 video frames over 44 seconds. After stacking the 40 best frames and further processing, the following image emerged as my only decent picture. Mercury is a well-defined black dot on the right with an apparent angular diameter of about 10 arc seconds. 

The featureless solar disc had no sunspots or filaments. Therefore, Mercury always appeared against a nearly homogeneous background of disc spicules. Other Mercury images I captured were flawed in some way and not worth display. 

Only one other image from this day was worthwhile. A small eruption was visible on the southeastern solar limb. The next picture shows the outburst. There are also three barely visible vertical bands in the image that remain after a flawed flat field calibration. 

The eruption above was associated with a small, newly emerged sunspot which rotated into view in the next couple of days. This quickly dying sunspot was a member of the next solar cycle which will slowly begin producing more sunspots in coming years.

Clouds can be so frustrating! The sky was completely clear all day on the day before the transit, and the sky unexpectedly cleared almost immediately after the transit ended! During the transit itself, however, bad luck!