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Monday, May 9, 2016
Transit of Mercury
I was clouded out for most of today's transit of Mercury, but in mid-afternoon the skies cleared briefly and I was able to observe the transit visually and capture the following picture through thin clouds.
Mercury is the dark black dot at the left, along the 10 o'clock direction from the centre of the Sun. The shading on the Sun's surface is due to the thin clouds through which I took this picture. Note how much darker Mercury's disc is than the sunspot group (Active Region 12542).
The photo was taken at 13:43 UTC from the Fourmilab driveway with a Nikon D600 camera. Exposure was 1/1250 second at the fixed f/8 aperture of the Nikon 500 mm catadioptric "mirror lens" with ISO 400 sensitivity. A full aperture Orion solar filter was mounted on the front of the lens. This image is cropped from the full frame and scaled down to fit on the page. Minor contrast stretching and sharpening was done with GIMP.
For comparison, below is an image of the transit from space, captured by the Solar Dynamics Observatory's (SDO) Helioseismic and Magnetic Imager.
The image appears rotated with respect to mine because solar north is up in the SDO image, while mine shows the Sun as it appears from my location at 47° north latitude.
Posted at
19:49
