APOD: Northern Equinox Eclipse (2015 Mar 21)

Comments and questions about the APOD on the main view screen.
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APOD: Northern Equinox Eclipse (2015 Mar 21)

Post by APOD Robot » Sat Mar 21, 2015 4:08 am

Image Northern Equinox Eclipse

Explanation: Snowy and cold is weather you might expect at the start of spring for Longyearbyen on the Arctic archipelago of Svalbard, Norway. But that turned out to be good weather for watching the Moon's umbral shadow race across northern planet Earth. The region was plunged into darkness for 3 minutes during the March 20 total solar eclipse while insulated eclipse chasers witnessed the dark Sun in the cold clear sky. In this well-timed snapshot captured near the end of totality, the Moon's shadow sweeps away from the horizon and the solar corona fades as the lunar disk just begins to uncover the Sun. Streaming past the Moon's edge, direct rays of sunlight create the fleeting appearance of a glistening diamond ring.

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Re: APOD: Northern Equinox Eclipse (2015 Mar 21)

Post by Nitpicker » Sat Mar 21, 2015 5:03 am

(Nothing to do with focal reducers, but) I've quite enjoyed the impressive collection of images of this eclipse, posted on The Starship, including this APOD. As an aside, I've noted that in quite a few of these images, the Moon appears darker than the surrounding sky at totality, which I suppose is an illusion of some kind, but it still makes me think that the criticism of the APOD from March 15, was perhaps a little unfair: http://apod.nasa.gov/apod/ap150315.html & http://asterisk.apod.com/viewtopic.php?t=34546.

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Re: APOD: Northern Equinox Eclipse (2015 Mar 21)

Post by geckzilla » Sat Mar 21, 2015 6:38 am

Nitpicker wrote:I've noted that in quite a few of these images, the Moon appears darker than the surrounding sky at totality, which I suppose is an illusion of some kind, but it still makes me think that the criticism of the APOD from March 15, was perhaps a little unfair
All you have to do is look at the series of photos that were used to create the dynamic range image, though. See link. It's ok if there is a slight difference but the 15th's was just way too dark. I mean, look at the first image. How does the moon go from being lighter than the ground to being darker than it? Because the range processing was done for everything but the moon.
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Re: APOD: Northern Equinox Eclipse (2015 Mar 21)

Post by Nitpicker » Sat Mar 21, 2015 8:36 am

geckzilla wrote:
Nitpicker wrote:I've noted that in quite a few of these images, the Moon appears darker than the surrounding sky at totality, which I suppose is an illusion of some kind, but it still makes me think that the criticism of the APOD from March 15, was perhaps a little unfair
All you have to do is look at the series of photos that were used to create the dynamic range image, though. See link. It's ok if there is a slight difference but the 15th's was just way too dark. I mean, look at the first image. How does the moon go from being lighter than the ground to being darker than it? Because the range processing was done for everything but the moon.
The APOD from the 15th was said to "realistically simulate how the adaptive human eye saw the eclipse" and also to "convey the feeling of the eclipse, the emotions it evoked, rather than be a strict scientifically precise representation". It was not referring to the exposure of the foreground. And your original criticism was comparing the darkness of the sky with the darkness of the Moon. My point is only that the Moon appears darker than the surrounding sky in a number of the (single exposure) photographs of yesterday's eclipse, too.

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Re: APOD: Northern Equinox Eclipse (2015 Mar 21)

Post by Morlock » Sat Mar 21, 2015 1:15 pm

When in Madagascar, I saw an eclipse and got as far away from people as I could and had a wonderful experience. However, in Svalbard, they were smart to get out in groups so as to make it easier to deal with polar bears. I believe you're not supposed to leave the town unarmed, not kidding.

However, word among the polar bears was, "Wait until the eclipse, it will be dark and they'll be distracted. It's only a few minutes but you'll get supper."

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Re: APOD: Northern Equinox Eclipse (2015 Mar 21)

Post by geckzilla » Sat Mar 21, 2015 2:39 pm

Nitpicker wrote:The APOD from the 15th was said to "realistically simulate how the adaptive human eye saw the eclipse" and also to "convey the feeling of the eclipse, the emotions it evoked, rather than be a strict scientifically precise representation". It was not referring to the exposure of the foreground. And your original criticism was comparing the darkness of the sky with the darkness of the Moon. My point is only that the Moon appears darker than the surrounding sky in a number of the (single exposure) photographs of yesterday's eclipse, too.
Only slightly darker! And it's definitely possible that some form of HDR processing was done on the new photographs as it was the old one. I wouldn't say it's easy to tell a good single exposure from a very mild dynamic range image comprised of even just two images. You can brush aside the criticism by saying it was just to convey a feeling but then you'd have to leave yourself open to a different kind of criticism: whether or not the image feels like an eclipse. Then I don't even have to get technical. I can just say it feels wrong.
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Re: APOD: Northern Equinox Eclipse (2015 Mar 21)

Post by Chris Peterson » Sat Mar 21, 2015 2:48 pm

Nitpicker wrote:(Nothing to do with focal reducers, but) I've quite enjoyed the impressive collection of images of this eclipse, posted on The Starship, including this APOD. As an aside, I've noted that in quite a few of these images, the Moon appears darker than the surrounding sky at totality, which I suppose is an illusion of some kind, but it still makes me think that the criticism of the APOD from March 15, was perhaps a little unfair: http://apod.nasa.gov/apod/ap150315.html & http://asterisk.apod.com/viewtopic.php?t=34546.
There is certainly an illusion because of the bright corona. But if you can measure it in the image, it's a processing artifact.
Chris

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Re: APOD: Northern Equinox Eclipse (2015 Mar 21)

Post by neufer » Sat Mar 21, 2015 3:31 pm

Chris Peterson wrote:
Nitpicker wrote:
I've noted that in quite a few of these images, the Moon appears darker than the surrounding sky at totality, which I suppose is an illusion of some kind, but it still makes me think that the criticism of the APOD from March 15, was perhaps a little unfair: http://apod.nasa.gov/apod/ap150315.html & http://asterisk.apod.com/viewtopic.php?t=34546.
There is certainly an illusion because of the bright corona. But if you can measure it in the image, it's a processing artifact.
While Earthshine on the Moon plus atmospheric light must (by definition) exceed nearby atmospheric light alone
the lower down lights of Longyearbyen on the other side of the mountain are brighter than both.
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Re: APOD: Northern Equinox Eclipse (2015 Mar 21)

Post by Chris Peterson » Sat Mar 21, 2015 3:37 pm

neufer wrote:While Earthshine on the Moon plus atmospheric light must (by definition) exceed nearby atmospheric light alone the lower down lights of Longyearbyen on the other side of the mountain are brighter than both.
Absolutely. It is the region right around the Sun/Moon that is relevant.
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Re: APOD: Northern Equinox Eclipse (2015 Mar 21)

Post by BMAONE23 » Sat Mar 21, 2015 3:58 pm

The region was plunged into darkness for 3 minutes during the March 20 total solar eclipse while insulated eclipse chasers witnessed the dark Sun in the cold clear sky. In this well-timed snapshot captured near the end of totality, the Moon's shadow sweeps away from the horizon and the solar corona fades as the lunar disk just begins to uncover the Sun. Streaming past the Moon's edge, direct rays of sunlight create the fleeting appearance of a glistening diamond ring.

One ring to rule them all, one ring to find them,
One ring to bring them all and in the darkness bind them.

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Re: APOD: Northern Equinox Eclipse (2015 Mar 21)

Post by Nitpicker » Sun Mar 22, 2015 12:37 am

geckzilla wrote:Only slightly darker! <snip> You can brush aside the criticism by saying it was just to convey a feeling but then you'd have to leave yourself open to a different kind of criticism: whether or not the image feels like an eclipse. Then I don't even have to get technical. I can just say it feels wrong.
And I only said I thought the criticism was perhaps a little unfair. I feel the author of an image is entitled to say whether or not it is an accurate representation of the feelings evoked by the experience of being there. The author's intention is important. (Having said that, I doubt the adaptive human eye could have seen all of that in the same instant. The eye needs time to adjust in order to achieve its wide dynamic range. But perhaps that was the intended meaning of the APOD caption [for March 15, that is.])