Question regarding lunar eclipses in general

[Entropy]

Hi all,

I just have a generalquestion regarding lunar eclipses.

It takes 1hr for it to reach totality and then 1.5hrs spent in totality, why does the moon hold in this alignment for 90minutes ? if it doesnt why does it apear red for the 90minutes ?

Thanks
Scott

[RB (Andrew)]

Have a look at this diagram which illustrates what is taking place.
August Lunar Eclipse
The Earth's shadow, the umbra, casts a darker shadow area than the fringe penumbra shadow area on either side hence the time difference that the moon spends traveling through each respective region.
The earth's atmosphere refracts the other colours and only allows the red wavelength through which turns the moon a blood red.

[sheeny (Al)]

Originally Posted by Entropy

Hi all,

I just have a generalquestion regarding lunar eclipses.

It takes 1hr for it to reach totality and then 1.5hrs spent in totality, why does the moon hold in this alignment for 90minutes ? if it doesnt why does it apear red for the 90minutes ?

Thanks
Scott

G'Day Scott,

The moon doesn't really "hold" the eclipse alignment, it keeps moving through the shadow of the earth.

If you think about a solar eclipse for a moment, the moon just happens to be roughly the same apparent size as the sun in the sky, so the period of totality in a solar eclipse is very short.

In a lunar eclipse, the earth is between the sun and moon, and of course the earth is much bigger than the moon, so it takes longer for the moon to moove though the earth's umbra (darkest part of the shadow) - about 1.5 hours as you say.

The reason the moon is red during this time is that light passing through the earth's atmosphere is scattered. The high frequencies are scattered most (due to the nitrogen in the atmosphere) so the red colours pass though better but are scattered enough to illuminate the moon a little bit. Dust in the atmosphere also adds to the red colour.

Al.

[Geoff45 (Geoff)]

If you were on the moon you would have a spectacular sight of a bright red/orange ring surrounding the black night side of the earth.
Geoff

[Blue Skies (Jacquie)]

Hmmm, now that presents a future challenge for eclipse chasers! I can just see it now, Antarctica is no longer the final frontier...

[Pondero]

I have no idea what it holds for totality. My question is about Lat 79.5 W. I am wondering what I will observe of the eclipse which won't be total for me ( I am told). In Toronto we are GMT -5 hours .

[iceman (Mike)]

Hi Pondero.

Going by the NASA Eclipse Chart in the article, at your Longitude the eclipse will only be visible at moonset. So you may only see the final stages of the eclipse as the Moon is setting low in the West.

I hope you still get to see it and I'd love to see some photos.