A total solar eclipse occurred on October 27, 1780. A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby totally or partly obscuring the image of the Sun for a viewer on Earth. A total solar eclipse occurs when the Moon's apparent diameter is larger than the Sun's, blocking all direct sunlight, turning day into darkness. Totality occurs in a narrow path across Earth's surface, with the partial solar eclipse visible over a surrounding region thousands of kilometres wide.

During the American Revolutionary War, the first American solar eclipse expedition was organized and sent out from Harvard College in Massachusetts. A special immunity agreement was negotiated with the British to allow the scientists to work unharmed. The Harvard expedition, after all their efforts, missed the eclipse because they chose a site outside the path of totality. Modern analysis of this embarrassing incident for embryonic American science blames Samuel Williams for miscalculating the path of totality.^[1]

It is a part of solar Saros 120.

• List of solar eclipses visible from the United Kingdom 1000–2090 AD