description Andre-Louis Danjon Overview
Andre-Louis Danjon was a French astronomer who directed the Paris Observatory. He is especially associated with the Danjon scale, a system he proposed in 1921 for describing the brightness and visual appearance of the Moon during a total lunar eclipse. The scale connects a named astronomical instrument of observation with a practical classification of eclipse darkness, making Danjon's name familiar in observational lunar astronomy.
help Andre-Louis Danjon FAQ
Who was Andre-Louis Danjon?
Andre-Louis Danjon was a French astronomer who directed the Paris Observatory. He is especially remembered for his work on lunar eclipses and observational astronomy.
What is the Danjon scale?
The Danjon scale describes the brightness and color of the Moon during a total lunar eclipse. Danjon proposed it in 1921 using a five-step scale from very dark eclipses to bright coppery ones.
When is the Danjon scale used?
It is used during total lunar eclipses, when the Moon passes through Earth's umbral shadow. Observers estimate the Moon's appearance and assign a Danjon value from 0 to 4.
What affects a lunar eclipse's Danjon rating?
Dust and aerosols in Earth's atmosphere can reduce the sunlight refracted into the shadow, making the eclipsed Moon look darker or redder. Local observing conditions and the Moon's position in the shadow also affect visual impressions.
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