This image was taken in May of 2016. Mercury last transited the sun in 2019 and the next transit is in 2032. Mercury transits the sun every few years from our vantage point on Earth. Transits occur 13 times or so every 100 years. I was blessed to capture this image on a clear day from my backyard using the Astro-Physics AP160EDF refractor and a Canon 6D DSLR. There are several sunspots visible in the image as well.
Animated gif of the Mercury transit
