27 August 1883 Waning Crescent, 30% lit

Krakatoa erupts

Krakatoa's explosions were heard 3,080 miles away, and for weeks afterwards the Sun and Moon looked blue or green across the tropics.

The Royal Society's inquiry collected the reports: in the tropics the haze turned the Sun and Moon blue or green continuously for the first few weeks, while farther north it happened only now and then, and many of the "green moons" there were a contrast effect against the pink twilight. The particles did the work: plumes full of specks about a micron across, close to the wavelength of red light, which scatter red and let blue through.

Date: 27 August 1883
Moon computed for: 10:00 local time, UTC+7:02
Phase: Waning Crescent
Illuminated: 30%

Source: Royal Society, The Eruption of Krakatoa, and Subsequent Phenomena (1888) (opens in a new tab)

NASA Science, Summer Blue Moon (2015) (opens in a new tab) for the micron-sized particles, and why they turn the Moon blue

Documented unusual sky · regional context

A blue and green Sun and Moon after Krakatoa

After the eruption of 26 and 27 August 1883 the haze in the upper air turned the Sun and Moon blue or green across the tropics, continuously for the first few weeks. At Madras on 12 September the Moon near the horizon went pale green. The last clear report of a green Sun in the continuous series was from a ship near the equator on 28 September.

Where: the tropics, from southern India and Ceylon to ships in the Indian Ocean and near the equator. Regional context from reports collected at the time. Farther north the colours appeared only now and then, and the Royal Society's committee thought many of those were a contrast effect against pink twilight. It is not a record of any one person's sky.

Source: Royal Society, The Eruption of Krakatoa, and Subsequent Phenomena (1888), Part IV (opens in a new tab)

Krakatoa erupts

Settings

Gear that makes it better

Where these numbers come from

Krakatoa erupts

Under the same moon