Chris McKitterick (mckitterick) wrote,
Chris McKitterick
mckitterick

Astro-images of the day: Lunar eclipse & composite shot

So if you had been able to watch the full run of the eclipse last night (er, early this morning), this is what you could have seen (each part of the composite is about twenty minutes apart):

Click the image to see the story.

If you woke up during the totality and the sky was clear, you probably saw something like this:


Unfortunately, unless you're on the West Coast of the US, you probably had to drive to the top of a hill or into the countryside to get a clear view; in Lawrence, it was pretty much hidden by trees. However, seeing a blood-red Moon - even through trees, even for a few minutes while dead-tired (it was 5am, after all) - was just way cool.

EDIT: Here's some info from Wikipedia about why the Moon turns red during an eclipse:

The red colouring arises because sunlight reaching the Moon must pass through a long and dense layer of the Earth's atmosphere, where it is scattered. Shorter wavelengths are more likely to be scattered by the small particles, and so by the time the light has passed through the atmosphere, the longer wavelengths dominate. This resulting light we perceive as red. This is the same effect that causes sunsets and sunrises to turn the sky a reddish colour; an alternative way of considering the problem is to realise that, as viewed from the Moon, the Sun would appear to be setting (or rising) behind the Earth.

The amount of refracted light depends on the amount of dust or clouds in the atmosphere; this also controls how much light is scattered. In general, the dustier the atmosphere, the more that other wavelengths of light will be removed (compared to red light), leaving the resulting light a deeper red colour. This causes the resulting coppery-red hue of the Moon to vary from one eclipse to the next. Volcanoes are notable for expelling large quantities of dust into the atmosphere, and a large eruption shortly before an eclipse can have a large effect on the resulting colour.

The following scale (the Danjon scale) was devised by André Danjon for rating the overall darkness of lunar eclipses:

L=0: Very dark eclipse. Moon almost invisible, especially at mid-totality.
L=1: Dark Eclipse, gray or brownish in colouration. Details distinguishable only with difficulty.
L=2: Deep red or rust-colored eclipse. Very dark central shadow, while outer edge of umbra is relatively bright.
L=3: Brick-red eclipse. Umbral shadow usually has a bright or yellow rim.
L=4: Very bright copper-red or orange eclipse. Umbral shadow has a bluish, very bright rim.

Best,
Chris
Tags: astronomy
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