Black drop effect
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The black drop effect is an optical phenomenon visible during a transit of Venus and, to a lesser extent, a transit of Mercury.
Venus transits the face of the Sun on 8 June 2004. Here, the black drop effect is visible.
The black drop effect as observed by Captain James Cook and Charles Green in 1771.
The black drop effect in 2004, in moments of "bad" seeing (left) and "good" seeing (right).
Limb darkening
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Limb darkening is an optical effect seen in stars and planets, where the central part of the disk appears brighter than the edge, or limb. Its understanding offered early solar astronomers an opportun
Black drop effect
…drop effect, or at least that it was much less pronounced than had been reported in earlier centuries' transits. Larger telescopes, better optics, and limb darkening may have been factors. The Shuckburgh telescope of the Royal Observatory, Greenwich in London was used for the 1832 transit of Mercury. It was equipped…
A filtered image of the Sun in visible light, showing the limb-darkening effect as a dimmer luminosity towards the edge or limb of the solar disk. The image was taken during the 2012 transit of Venus (seen here as the dark spot at the upper right).