APOD: A Fleeting Double Eclipse of the Sun (2017 Aug 28)

Comments and questions about the APOD on the main view screen.
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APOD: A Fleeting Double Eclipse of the Sun (2017 Aug 28)

Postby APOD Robot » Mon Aug 28, 2017 4:06 am

Image A Fleeting Double Eclipse of the Sun

Explanation: Last week, for a fraction of a second, the Sun was eclipsed twice. One week ago today, many people in North America were treated to a standard, single, partial solar eclipse. Fewer people, all congregated along a narrow path, experienced the eerie daytime darkness of a total solar eclipse. A dedicated few with fast enough camera equipment, however, were able to capture a double eclipse -- a simultaneous partial eclipse of the Sun by both the Moon and the International Space Station (ISS). The Earth-orbiting ISS crossed the Sun in less than a second, but to keep the ISS from appearing blurry, exposure times must be less than 1/1000th of a second. The featured image composite captured the ISS multiple times in succession as it zipped across the face of the Sun. The picture was taken in a specific color emitted by hydrogen which highlights the Sun's chromosphere, a layer hotter and higher up than the usually photographed photosphere.

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Re: APOD: A Fleeting Double Eclipse of the Sun (2017 Aug 28)

Postby Boomer12k » Mon Aug 28, 2017 4:31 am

Although I believe technically the ISS is a Transit... though I made the comment that it was an Annular and Total Eclipse on the other APOD the other day... but we don't really call it a "Venus Eclipse"... right?

But these Eclipse shots with the ISS, are cool... 8-)

This one has great Solar detail. and Sunspots...

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Re: APOD: A Fleeting Double Eclipse of the Sun (2017 Aug 28)

Postby RocketRon » Mon Aug 28, 2017 4:59 am

What sort of camera equipment/telescope can actually do that ?

Even without the partial eclipse or ISS transit, that would be a great photo of ole Sol.
Or series of them, over time....

heehaw

Re: APOD: A Fleeting Double Eclipse of the Sun (2017 Aug 28)

Postby heehaw » Mon Aug 28, 2017 9:24 am

Seeing such photos makes me think of a barber (because eclipse your hair).

RogerV

Re: APOD: A Fleeting Double Eclipse of the Sun (2017 Aug 28)

Postby RogerV » Mon Aug 28, 2017 1:02 pm

The chromosphere is described here as higher and hotter than the photosphere. Oops!

An amazing picture, nevertheless. :D

-- Roger V

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Re: APOD: A Fleeting Double Eclipse of the Sun (2017 Aug 28)

Postby barliman » Mon Aug 28, 2017 1:27 pm

I agree: it should have been titled "A Fleeting Eclipse/Transit"

And I agree: it looks cool.

Guest

Re: APOD: A Fleeting Double Eclipse of the Sun (2017 Aug 28)

Postby Guest » Mon Aug 28, 2017 1:28 pm

Or perhaps "A Fleeting Double Crossing", with a brief mention of the difference between an eclipse and a transit.

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Re: APOD: A Fleeting Double Eclipse of the Sun (2017 Aug 28)

Postby Chris Peterson » Mon Aug 28, 2017 1:39 pm

RocketRon wrote:What sort of camera equipment/telescope can actually do that ?

Nothing particularly special. You can catch a partial eclipse or an ISS transit with a very basic telescope and ordinary DSLR. If you want to see more structure on the Sun or see prominences, you need a telescope with a very narrow hydrogen-alpha filter. Such telescopes are somewhat more expensive than unfiltered scopes of the same aperture, but are nevertheless quite common amateur astronomer kit.
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Re: APOD: A Fleeting Double Eclipse of the Sun (2017 Aug 28)

Postby Chris Peterson » Mon Aug 28, 2017 1:41 pm

RogerV wrote:The chromosphere is described here as higher and hotter than the photosphere. Oops!

The chromosphere is higher and hotter than the photosphere.
Chris

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Re: APOD: A Fleeting Double Eclipse of the Sun (2017 Aug 28)

Postby MarkBour » Mon Aug 28, 2017 2:51 pm

Yay! NASA has posted enough different perspectives on the eclipse to fully satisfy me. And then some!
https://www.nasa.gov/eclipselive

The lucky astronauts on the ISS got to see 3 eclipses (at least partial) on Aug 21.
https://eclipse2017.nasa.gov/iss-observations
But for all of that, they did not get to see a total eclipse (same reference).

The transit for today's APOD looks different than another one I saw on NASA's site:
https://www.nasa.gov/sites/default/files/thumbnails/image/36670875426_39d028e28a_o.jpg
I'm thinking they were from different orbits of the ISS. This latter sequence had me thinking they experienced totality during it. Must have just been an interesting perspective, though.

And here's one other really cool shot from that treasure-trove:
https://www.nasa.gov/sites/default/files/thumbnails/image/iss052e056245.jpg
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Re: APOD: A Fleeting Double Eclipse of the Sun (2017 Aug 28)

Postby ta152h0 » Mon Aug 28, 2017 5:12 pm

I was hoping some lucky cameraman would catch the RB57 like that
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Re: APOD: A Fleeting Double Eclipse of the Sun (2017 Aug 28)

Postby RJN » Mon Aug 28, 2017 6:15 pm

At the request of the astrophotographer, the location from which the image was taken: Huron, CA, was added to the APOD text.
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Re: APOD: A Fleeting Double Eclipse of the Sun (2017 Aug 28)

Postby alter-ego » Tue Aug 29, 2017 4:44 am

MarkBour wrote:...
The transit for today's APOD looks different than another one I saw on NASA's site:
https://www.nasa.gov/sites/default/files/thumbnails/image/36670875426_39d028e28a_o.jpg
I'm thinking they were from different orbits of the ISS. This latter sequence had me thinking they experienced totality during it. Must have just been an interesting perspective, though.
...

They're the same orbit.
Lacking the photographer's coordinates, I can say at Huron ± several km, the transit time was 16:41:11UT ± few seconds.
For the Wyoming transit I posted, the transit time was 16:43:53UT ± 1 second about.
The NASA link you posted looks similar to the Wyoming transit, but it too may not be in the totality zone and thus not in Wyoming. It's similar enough though that it's quite reasonable to assume it's easily within 10 minutes of today's APOD transit time.

Edit: The image in question was taken near Banner, Wyoming, and confirms the 3 transits we're talking about occurred during the same ISS pass.
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Re: APOD: A Fleeting Double Eclipse of the Sun (2017 Aug 28)

Postby tedrey » Tue Aug 29, 2017 11:46 am

I'm obviously confused. If the ISS transited the sun (angular diameter of one half degree) in one second, wouldn't it cover 360 degrees in 720 seconds, and orbit the earth in 12 minutes, rather than 90? I'm willing to be proved stupid to increase my understanding.

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Re: APOD: A Fleeting Double Eclipse of the Sun (2017 Aug 28)

Postby NGC3314 » Tue Aug 29, 2017 1:29 pm

tedrey wrote:I'm obviously confused. If the ISS transited the sun (angular diameter of one half degree) in one second, wouldn't it cover 360 degrees in 720 seconds, and orbit the earth in 12 minutes, rather than 90? I'm willing to be proved stupid to increase my understanding.


What's missing there is that the orbit of ISS is not very high compared to the Earth's diameter, so an observer on the ground sees it for only a small fraction of an orbit (roughly 5 minutes out of 93 minutes, depending on how nearly overhead a pass is). If you apply the same reasoning to a satellite in geosynchronous orbit, which is many Earth radii from its center, you do get the expected result (although in that case you have to use motion against a background object rather than horizon-to-horizon time).

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Re: APOD: A Fleeting Double Eclipse of the Sun (2017 Aug 28)

Postby ta152h0 » Tue Aug 29, 2017 6:10 pm

I remember the astronauts on the ISS saying they will be 1500 miles away from the totality shadow.
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Re: APOD: A Fleeting Double Eclipse of the Sun (2017 Aug 28)

Postby Fraughtful Joe » Wed Aug 30, 2017 4:40 pm

tedrey wrote:I'm willing to be proved stupid to increase my understanding.


Temporarily ignorant, perhaps but not stupid. There's no cure for stupidity. Deniers of climate change in the face of empirical evidence are an example of that breed.
I learned something here ,too. Thanks to you for the question and NGC3314 for the explanation!

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Re: APOD: A Fleeting Double Eclipse of the Sun (2017 Aug 28)

Postby neufer » Fri Sep 01, 2017 6:00 pm

RJN wrote:
At the request of the astrophotographer, the location from which the image was taken: Huron, CA, was added to the APOD text.
https://eclipse2017.nasa.gov/iss-observations wrote:
ISS Transit Across the Sun: While an ISS transit of the Sun will occur over a very thin ground track from California through Canada, only at the intersection of this transit path with the Moon’s shadow path in Wyoming can one stay in one place and witness both a transit of the ISS across the partially eclipsed Sun and the total solar eclipse later in the morning.
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Re: APOD: A Fleeting Double Eclipse of the Sun (2017 Aug 28)

Postby alter-ego » Sat Sep 02, 2017 3:20 am

neufer wrote:
RJN wrote:
At the request of the astrophotographer, the location from which the image was taken: Huron, CA, was added to the APOD text.
https://eclipse2017.nasa.gov/iss-observations wrote:
ISS Transit Across the Sun: While an ISS transit of the Sun will occur over a very thin ground track from California through Canada, only at the intersection of this transit path with the Moon’s shadow path in Wyoming can one stay in one place and witness both a transit of the ISS across the partially eclipsed Sun and the total solar eclipse later in the morning.

And of the 4 consecutive ISS passes across the contiguous US, only the last two shadow tracks (3rd through California and Wyoming and 4th through Washington state) occurred during the eclipse which resulted in transits simultaneous with a partial eclipse. Only near Burris, WY was totality and a transit visible from the same location.
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