APOD: Perseid in Moonlight (2014 Aug 15)

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APOD: Perseid in Moonlight (2014 Aug 15)

Postby APOD Robot » Fri Aug 15, 2014 4:07 am

Image Perseid in Moonlight

Explanation: Bright moonlight from a Full Moon near perigee illuminates the night and casts shadows in this skyscape from central Iran. Taken on August 12, near the peak of the annual Perseid meteor shower the exposure also captures a bright and colorful perseid streak above the shady tree in the foreground. This year the super moonlight interfered with meteor watching into the early morning hours, overwhelming the trails from many fainter perseids in the shower. Brighter perseids like this one were still visible though, their trails pointing back to the heroic constellation Perseus outlined at the right. Swept up as planet Earth orbits through dust left behind from periodic comet Swift-Tuttle, the cosmic grains that produce perseid meteors enter the atmosphere at nearly 60 kilometers per second, heated to incandesence and vaporized at altitudes of about 100 kilometers. Next year, Perseid meteors will flash through dark skies under a New Moon.

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Re: APOD: Perseid in Moonlight (2014 Aug 15)

Postby geckzilla » Fri Aug 15, 2014 4:10 am

Interesting. What's with the spectrum of colors in the meteor trail? Is this an optical artifact?
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Re: APOD: Perseid in Moonlight (2014 Aug 15)

Postby Boomer12k » Fri Aug 15, 2014 5:48 am

Cool...

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Re: APOD: Perseid in Moonlight (2014 Aug 15)

Postby rwlott » Fri Aug 15, 2014 2:02 pm

Bright moonlight I understand, but this appears to be almost full daylight. I wonder what time of the night or early morning hours this image was taken and what length of exposure was used to capture this much light?

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Re: APOD: Perseid in Moonlight (2014 Aug 15)

Postby Chris Peterson » Fri Aug 15, 2014 2:09 pm

rwlott wrote:Bright moonlight I understand, but this appears to be almost full daylight. I wonder what time of the night or early morning hours this image was taken and what length of exposure was used to capture this much light?

Any exposure of a few seconds made with a bright moon will be essentially indistinguishable from a daylight image.

The full Moon is 400,000 times dimmer than the Sun, and that's a brightness ratio easily accommodated by the choice of exposure time, aperture, and ISO.
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Re: APOD: Perseid in Moonlight (2014 Aug 15)

Postby CURRAHEE CHRIS » Fri Aug 15, 2014 3:18 pm

What a really neat picture!!!

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Re: APOD: Perseid in Moonlight (2014 Aug 15)

Postby starsurfer » Fri Aug 15, 2014 4:44 pm

Wil Tirion is one of my astronomical heroes, his starcharts are of exquisite quality.

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Re: APOD: Perseid in Moonlight (2014 Aug 15)

Postby Rusty Brown in Cda » Fri Aug 15, 2014 5:29 pm

Late at night, a "new moon" is actually no moon at all, since the "new" moon occurs only when the moon and sun are near each other in the sky, so both would have already set. Not to be too pedantic about it, I hope.

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Re: APOD: Perseid in Moonlight (2014 Aug 15)

Postby John Erickson » Fri Aug 15, 2014 6:29 pm

The revised version of the image (linked to on the page under the description) is more complete in terms of labels and inclusion of stars, but I would hesitate to call it "more correct." The way an asterism is presented is a matter of choice rather than a matter of accuracy.

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Re: APOD: Perseid in Moonlight (2014 Aug 15)

Postby Chris Peterson » Fri Aug 15, 2014 6:33 pm

Rusty Brown in Cda wrote:Late at night, a "new moon" is actually no moon at all, since the "new" moon occurs only when the moon and sun are near each other in the sky, so both would have already set. Not to be too pedantic about it, I hope.

Well, during the peak of the 2015 Perseids the Moon will actually be "old"- a waning crescent two days before new. So when the Perseid radiant is at the zenith, near dawn, there actually will be a visible Moon low in the eastern sky, rising before the Sun.
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Re: APOD: Perseid in Moonlight (2014 Aug 15)

Postby Cousin Ricky » Fri Aug 15, 2014 8:07 pm

John Erickson wrote:The revised version of the image (linked to on the page under the description) is more complete in terms of labels and inclusion of stars, but I would hesitate to call it "more correct." The way an asterism is presented is a matter of choice rather than a matter of accuracy.


That was my thought exactly.

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Re: APOD: Perseid in Moonlight (2014 Aug 15)

Postby DavidLeodis » Sat Aug 16, 2014 2:18 pm

I've learnt some new words (well they are to me :P ) through APODs. A little while back it was spaghettification (July 21 2014) and from the APOD of August 15 2014 (through the 'Wil Tirion' link) it is uranography, of which it states "Uranography = Sky cartography". I must admit I thought uranography might be to do with Uranus.

PS. Is it known what the bright light is? I assume it is the reflection of the Moon on some object, but I'm unsure.

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Re: APOD: Perseid in Moonlight (2014 Aug 15)

Postby Chris Peterson » Sat Aug 16, 2014 2:39 pm

DavidLeodis wrote:PS. Is it known what the bright light is? I assume it is the reflection of the Moon on some object, but I'm unsure.

Most likely a house or yard light.
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Re: APOD: Perseid in Moonlight (2014 Aug 15)

Postby DavidLeodis » Sat Aug 16, 2014 3:39 pm

Thanks Chris. That does seem likely.

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Re: APOD: Perseid in Moonlight (2014 Aug 15)

Postby Ann » Sat Aug 16, 2014 4:33 pm

DavidLeodis wrote:I've learnt some new words (well they are to me :P ) through APODs. A little while back it was spaghettification (July 21 2014) and from the APOD of August 15 2014 (through the 'Wil Tirion' link) it is uranography, of which it states "Uranography = Sky cartography". I must admit I thought uranography might be to do with Uranus.

PS. Is it known what the bright light is? I assume it is the reflection of the Moon on some object, but I'm unsure.


In ancient Greece, Uranus was the god not of the planet that bears his name (since the planet hadn't been discovered at that time), but of the sky.

http://en.wikipedia.org/wiki/Uranus_(mythology) wrote:

Uranus (/ˈjʊərənəs/ or /jʊˈreɪnəs/; Ancient Greek Οὐρανός, Ouranos meaning "sky" or "heaven") was the primal Greek god personifying the sky.


Thanks for asking about that bright light. I was particularly interested in it because of its blue-green color.

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Re: APOD: Perseid in Moonlight (2014 Aug 15)

Postby DavidLeodis » Sat Aug 16, 2014 6:51 pm

Thanks Ann. :)

The bright light does have an interestingly noticeably blue-green colour.


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