Transit of Mercury

Mercury is passing in front of the Sun as I type. You can follow the Mercury transit until 0100 GMT (UT) via the Big Bear Solar Observatory‘s webcam. Here’s the start. You’re looking for the black dot that shifts.

Mercury Transit

Below is a version I’ve re-coloured, but hopefully you can see where the dot has moved.

Mercury recoloured

The reason the live image appears black and white is that the Big Bear Observatory is only looking at light in the H-Alpha wavelength, which means that it’s all one shade. This limitation that allows them to pick out features on the Sun better. Observations of this transit were used as a test of Einstein’s theory of Relativity.


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