Editing Danjon scale (section)

==Factors affecting the value of L==

Many factors can affect the appearance of the Moon during a lunar eclipse.  The Moon's path through the Earth's [[umbra]] is important, but so too are the current conditions of the [[Earth's atmosphere]].  While the Earth's shadow blocks any direct light from striking the Moon during a lunar eclipse, some light is refracted through the Earth's atmosphere giving the Moon a red hue.

The amount of light refracted affects the brightness of the moon at mid-eclipse, and this depends on several factors.  [[Volcanic]] eruptions are one of the most significant - eruptions which spew significant amounts of [[volcanic ash]] into the air are generally followed by several years of dark, deep red eclipses.  The effect of the [[1991 eruption of Mount Pinatubo]] on subsequent lunar eclipses was very noticeable, with the eclipse of 9 December 1992 rated 0 on the Danjon Scale by many observers.

It is also thought that the [[solar cycle]] has some effect on the darkness of lunar eclipses--indeed Danjon established the scale for this reason.