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 Post subject: Upcoming Eclipses
Unread postPosted: Thu Jan 22, 2009 9:29 am 
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Hey, this is a great idea for a forum. Is it new? I can only assume so as there hasn't been much discussion in here yet. I usually just hang around in the birding forums so I'm not always on top of what's going on in other parts of the forums but this is another of my keen interests.

Anyways, I trust most of you will know by now but for those who don't there will be an annular solar eclipse on Monday the 26th of January. The fact that it is an annular eclipse is rather irrelevant though as the path of annularity will pas some distance south of South Africa. From Cape Town the eclipse will be 72% total while us sorry sods up here in Jozi will only get 46%. Either way, I think it's exciting enough to warrant getting a solar filter. :mrgreen:

Whatever you do, just don't look at the eclipsed sun directly with the naked eye! You have been warned.

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 Post subject: Re: Annular Solar Eclipse, 26 Jan 2009
Unread postPosted: Thu Jan 22, 2009 9:37 am 
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Deefstes! :clap: Will be watching! :D
deefstes wrote:
Whatever you do, just don't look at the eclipsed sun directly with the naked eye! You have been warned.

I once set up my sorry excuse for a telescope :twisted: towards the sun and projected onto a piece of white paper so all the kids watch, I've just gotto figure it out again. 8)

Another easy and safe way of watching the eclipse:
Hold the kitchen sieve just above the ground, tilting its face towards the sun. Moving the sieve a little away from the ground, one can see an image of the sun forming, which will show the eclipse when it occurs.

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 Post subject: Re: Annular Solar Eclipse, 26 Jan 2009
Unread postPosted: Thu Jan 22, 2009 10:34 am 
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JenB wrote:
Another easy and safe way of watching the eclipse:
Hold the kitchen sieve just above the ground, tilting its face towards the sun. Moving the sieve a little away from the ground, one can see an image of the sun forming, which will show the eclipse when it occurs.


Cool, never heard of it but it sounds like a good plan. You can also just stick a hole in a sheet of paper with a pencil and use it to project an image of the sun on the floor or the wall.

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 Post subject: Re: Annular Solar Eclipse, 26 Jan 2009
Unread postPosted: Thu Jan 22, 2009 11:02 am 
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I look through the siver packet the tea bags come in...eg five roses. :D


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 Post subject: Re: Annular Solar Eclipse, 26 Jan 2009
Unread postPosted: Thu Jan 22, 2009 4:52 pm 
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Our teacher told us of this!
Will be watching! :D


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 Post subject: Re: Annular Solar Eclipse, 26 Jan 2009
Unread postPosted: Thu Jan 22, 2009 8:45 pm 
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I didn't know about the eclipse - thanks, Deefstes! 8) My son will be very excited! :D

And you're right: this is a new forum. 8)

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 Post subject: Re: Annular Solar Eclipse, 26 Jan 2009
Unread postPosted: Mon Jan 26, 2009 7:55 am 
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Just a reminder. Not ideal conditions in the Vaal Triangle at the mo, overcast, but it is visible every now and then. 8)


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 Post subject: Re: Annular Solar Eclipse, 26 Jan 2009
Unread postPosted: Mon Jan 26, 2009 8:03 am 
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Thanx for reminding me, GP! :clap: :D
Just had a look, it's cloudy but not too bad. 8)

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 Post subject: Re: Annular Solar Eclipse, 26 Jan 2009
Unread postPosted: Mon Jan 26, 2009 8:54 am 
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Yeah, the cloud cover is a bit of a nuisance but during a quick clearing about 15mins ago, I managed to snap this pic. Will keep looking to see if the conditions improve but unfortunately the eclipse will also deteriorate from here on. This pic was takeen just a few minutes after the maximum eclipse.
Image

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 Post subject: Re: Annular Solar Eclipse, 26 Jan 2009
Unread postPosted: Mon Jan 26, 2009 9:15 am 
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Thank you, deefstes! :clap:
Heavy clouds came over a while ago, at least now I've seen it! :D

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 Post subject: Re: Annular Solar Eclipse, 26 Jan 2009
Unread postPosted: Mon Jan 26, 2009 9:29 am 
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Thank you deefstes! :D


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 Post subject: Re: Upcoming Eclipses
Unread postPosted: Wed Jun 01, 2011 12:59 pm 
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I am hoping that a mite will give us info on the lunar ecclipse at full moon on 15 june.
Many thanks.


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 Post subject: Re: Upcoming Eclipses
Unread postPosted: Wed Jun 01, 2011 1:06 pm 
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Something like this?

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 Post subject: Re: Upcoming Eclipses
Unread postPosted: Wed Jun 01, 2011 3:41 pm 
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Not much more to add than the info DuQues provided but here's another important bit of info about the lunar eclipse - you're gonne freeze your butts off! :twisted:

But maybe now might be a good time to explain a little something about lunar eclipses in general. Unlike solar eclipses, the eclipse typically last much longer with a much slower onset and egress. Also, unlike solar eclipses, a lunar eclipse does not result in a complete invisibility of the moon but rather just an eerie red shadowy appearance of the moon.

The reason for this is that the moon is not obscured (like the sun is during a solar eclipse) but the sun's light that illuminates the moon is simply blocked off. Now you're asking "why then is the moon visible at all if no light falls on it?" and that's a very good question with a very interesting answer.

The moon appears reddish during full eclipse for the same reason a sunrise is reddish. If an astronaut would be standing on the moon during a total lunar eclipse he would see the earth gradually shifting in front of the sun, in much the same way we see the moon shifting in front of the sun during a solar eclipse. When the sun is fully eclipsed by the earth, Mr. Astronaut will see a reddish "sunrise" that extends all around the earth. I can imagine that would be a drop dead awesome sight to behold.

So that red light (which is red because all of the shorter wavelengths are absorbed by all of the earth's atmosphere that the light has to travel through) gets refracted inwards in the earth's atmosphere and then carries on to hit the moon.

Another thing that perhaps not everybody would know is that the moon can be eclipsed in two ways by the earth's shadow. This is best explained by a picture:
Image

Notice how the earth has three types of shadows, an umbra, a penumbra and an antumbra. The antumbra is irrelevant in the discussion of lunar eclipses because the moon is too close to earth that it could ever move through the antumbra but during any total lunar eclipse the moon will first move through the penumbra and eventually cross through the umbra and eventually moves through the penumbra again. The period during which the entire moon falls inside the umbra is what is known as the total eclipse (or "totality").

With some lunar eclipses the moon never even touches the umbra. This is called a penumbral eclipse and is barely visible. Some eclipses the moon does move into the umbra but leaves it again before moving into it entirely (sort of just skims it). This is called a partial lunar eclipse.

The moment the moon first enters or leaves these various zones are referred to as the "eclipse contacts" and for the lunar eclipse of 15 Jun are as follows (in South African time):

P1 = 19:24:33 (First contact, the moment the moon's leading edge touches and enters the earth's penumbral shadow. At this point nothing will be visible yet but the moon will gradually move into the penumbral shadow and get very slightly, almost imperceptibly, darker)

U1 = 20:22:55 (Second contact, the moment the moon's leading edge touches and enters the earth's umbral shadow. This also happens to be, almost exactly, the point when the moon's trailing edge last touches the penumbral shadow - because of, what I consider, the most mind blowing coincidence in astronomy but that's another explanation which will take up too much space. At this point the moon will be completely covered by the earth's penumbral shadow. The eclipse will be almost imperceptible but this is the start of the umbral eclipse.)

U2 = 21:22:29 (Third contact, the moment the moon's trailing edge touches and enters the earth's umbral shadow. This is the moment at which totality starts.)

U3 = 23:02:41 (Fourth contact, the moment the moon's leading edge touches and enters the earth's penumbral shadow again, and exits the earth's umbral shadow. This is the moment at which totality ends.)

U4 = 00:02:14 (Fifth contact, the moment the moon's trailing edge touches and exits the earth's umbral shadow. This is the moment at which the umbral eclipse is over.)

P4 = 01:00:44 (Sixth contact or last contact, the moment the moon's trailing edge touches and exits the earth's penumbral shadow. The show is officially over.)

This image illustrates these contact points:
Image

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 Post subject: Re: Upcoming Eclipses
Unread postPosted: Thu Jun 02, 2011 7:27 am 
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DuQues, thanks for the link. I think I must print the info. There should be some stuff in my sky guide 2011 as well.

Will be in Berg-en-dal the night of the 15th :dance:

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