APOD: Leonids Above Torre de la Guaita (2014 Nov 16)

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APOD: Leonids Above Torre de la Guaita (2014 Nov 16)

Post by APOD Robot » Sun Nov 16, 2014 5:10 am

Image Leonids Above Torre de la Guaita

Explanation: Leonids Meteor Shower came to an impressive crescendo in 1999. Observers in Europe saw a sharp peak in the number of meteors visible around 0210 UTC during the early morning hours of November 18. Meteor counts then exceeded 1000 per hour - the minimum needed to define a true meteor storm. At other times and from other locations around the world, observers typically reported respectable rates of between 30 and 100 meteors per hour. This photograph is a 20-minute exposure ending just before the main Leonids peak began. Visible are at least five Leonid meteors streaking high above the Torre de la Guaita, an observation tower used during the 12th century in Girona, Spain. In 2014, over the next few nights, the Leonids meteor shower will again peak. This year, although the crescent Moon should not create much competing skyglow, the Earth is predicted to pass through a more moderate stream of debris left over from Comet Tempel-Tuttle than in 1999, perhaps resulting in as many as 15 visible meteors per hour from dark locations.

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deathfleer

Re: APOD: Leonids Above Torre de la Guaita (2014 Nov 16)

Post by deathfleer » Sun Nov 16, 2014 6:39 am

why do they move in straight line while others in circcle?

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Re: APOD: Leonids Above Torre de la Guaita (2014 Nov 16)

Post by geckzilla » Sun Nov 16, 2014 8:10 am

deathfleer wrote:why do they move in straight line while others in circcle?
The ones with circular paths aren't moving. Those are stars and their trails are caused by Earth's rotation. The straight lines are moving quickly across the sky. They move so fast that in a single frame their entire trail is captured. Compare that to a star which may only add a single pixel to its trail for that exposure. It takes many exposures added together to create the star trails.
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dddavids49

Re: APOD: Leonids Above Torre de la Guaita (2014 Nov 16)

Post by dddavids49 » Sun Nov 16, 2014 1:01 pm

Why are there only 5 Leonids? I see many more streaks crossing the star arcs.

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Re: APOD: Leonids Above Torre de la Guaita (2014 Nov 16)

Post by Chris Peterson » Sun Nov 16, 2014 4:03 pm

geckzilla wrote:
deathfleer wrote:why do they move in straight line while others in circcle?
The ones with circular paths aren't moving. Those are stars and their trails are caused by Earth's rotation. The straight lines are moving quickly across the sky. They move so fast that in a single frame their entire trail is captured. Compare that to a star which may only add a single pixel to its trail for that exposure. It takes many exposures added together to create the star trails.
I would say that, with respect to the camera, the difference is that they are moving at very different speeds. Both are moving, however, and even the meteor trails are warped by the Earth's rotation (although we could never detect it visually).

EDIT: Also, this image was made in 1999. On film. It's a single 20-minute exposure, not a stack of exposures added together. How quickly we forget.
Last edited by Chris Peterson on Sun Nov 16, 2014 7:53 pm, edited 1 time in total.
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Re: APOD: Leonids Above Torre de la Guaita (2014 Nov 16)

Post by Chris Peterson » Sun Nov 16, 2014 4:08 pm

dddavids49 wrote:Why are there only 5 Leonids? I see many more streaks crossing the star arcs.
I'm guessing that only five of the meteors captured are reliably linked back to the Leonid radiant. The others are sporadic meteors or members of other showers. When I capture Leonids on my camera, I discard images of Southern Taurids, Northern Taurids, Alpha Monocerotids, and sporadics, all of which are occurring at the same time.
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guest345

Re: APOD: Leonids Above Torre de la Guaita (2014 Nov 16)

Post by guest345 » Sun Nov 16, 2014 7:25 pm

Double exposure?

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Re: APOD: Leonids Above Torre de la Guaita (2014 Nov 16)

Post by geckzilla » Sun Nov 16, 2014 9:30 pm

Chris Peterson wrote:EDIT: Also, this image was made in 1999. On film. It's a single 20-minute exposure, not a stack of exposures added together. How quickly we forget.
Heh, yeah, I just sat back down at my computer and looked at the picture again and then read the description and was about to correct myself when I saw your edit. I would make that assumption and have it be wrong.
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Re: APOD: Leonids Above Torre de la Guaita (2014 Nov 16)

Post by Chris Peterson » Sun Nov 16, 2014 10:33 pm

geckzilla wrote:I would make that assumption and have it be wrong.
I didn't question the assumption myself until the implications of the actual date of the image dawned on me.
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Re: APOD: Leonids Above Torre de la Guaita (2014 Nov 16)

Post by geckzilla » Sun Nov 16, 2014 10:37 pm

Chris Peterson wrote:
geckzilla wrote:I would make that assumption and have it be wrong.
I didn't question the assumption myself until the implications of the actual date of the image dawned on me.
The really funny thing is, if you look at the photo attentively enough, it's actually very easy to tell that it's most likely a single exposure just by how it looks. Double fail on my part for both missing that and not reading the description. :lol:
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Re: APOD: Leonids Above Torre de la Guaita (2014 Nov 16)

Post by ta152h0 » Mon Nov 17, 2014 3:16 am

Mr Geckzilla has an abundance of patience
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Re: APOD: Leonids Above Torre de la Guaita (2014 Nov 16)

Post by DavidLeodis » Mon Nov 17, 2014 1:36 pm

I got confused when the 'Leonids' link in the "In 2014, over the next few nights, the Leonids meteor shower will again peak" brings up information about the Geminids meteors that are due in December. :?

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Re: APOD: Leonids Above Torre de la Guaita (2014 Nov 16)

Post by DavidLeodis » Mon Nov 17, 2014 10:03 pm

dddavids49 wrote:Why are there only 5 Leonids? I see many more streaks crossing the star arcs.
The same base image has been used several times as an APOD but in all of the uses up to and including that of November 14 2004 there are only 5 obvious meteors, but in its use as the APOD of December 12 2010 and the current one there are a least 9 obvious meteors. The image would seem to have been reprocessed at some stage.