APOD: Aurora Slathers up the Sky (2017 Jul 29)

Comments and questions about the APOD on the main view screen.
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APOD Robot
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APOD: Aurora Slathers up the Sky (2017 Jul 29)

Postby APOD Robot » Sat Jul 29, 2017 4:09 am

Image Aurora Slathers up the Sky

Explanation: Like salsa verde on your favorite burrito, a green aurora slathers up the sky in this June 25 snapshot from the International Space Station. About 400 kilometers (250 miles) above Earth, the orbiting station is itself within the upper realm of the auroral displays. Aurorae have the signature colors of excited molecules and atoms at the low densities found at extreme altitudes. Emission from atomic oxygen dominates this view. The tantalizing glow is green at lower altitudes, but rarer reddish bands extend above the space station's horizon. The orbital scene was captured while passing over a point south and east of Australia, with stars above the horizon at the right belonging to the constellation Canis Major, Orion's big dog. Sirius, alpha star of Canis Major, is the brightest star near the Earth's limb.

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Boomer12k
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Re: APOD: Aurora Slathers up the Sky (2017 Jul 29)

Postby Boomer12k » Sat Jul 29, 2017 6:55 am

Awesome, sooooo cool.....

Got out the Evolution 6 tonight with friend. Moon, Jupiter, Saturn, M15, M13, M17, it was perfect viewing, though a the mobile home park....too many lights... still a great night. Sorry, no pix...

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Case
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Re: APOD: Aurora Slathers up the Sky (2017 Jul 29)

Postby Case » Sat Jul 29, 2017 12:22 pm

Image
What a nice view today’s APOD is. I always love auroras.

If I may nitpick, the stars in this photo have a sort of U-shape in detail, and the orientation of the U-shape changes from left to right in the photo. What may have caused that, and how does that geometry work?

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neufer
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Re: APOD: Aurora Slathers up the Sky (2017 Jul 29)

Postby neufer » Sat Jul 29, 2017 12:48 pm

Case wrote:
Image
What a nice view today’s APOD is. I always love auroras.

If I may nitpick, the stars in this photo have a sort of U-shape in detail, and the orientation of the U-shape changes from left to right in the photo. What may have caused that, and how does that geometry work?

    Coma :?:
https://en.wikipedia.org/wiki/Coma_(optics) wrote:
<<In optics (especially telescopes), the coma, or comatic aberration, in an optical system refers to aberration inherent to certain optical designs or due to imperfection in the lens or other components that results in off-axis point sources such as stars appearing distorted, appearing to have a tail (coma) like a comet. Specifically, coma is defined as a variation in magnification over the entrance pupil. In refractive or diffractive optical systems, especially those imaging a wide spectral range, coma can be a function of wavelength, in which case it is a form of chromatic aberration.

Coma is an inherent property of telescopes using parabolic mirrors. Unlike a spherical mirror, a bundle of parallel rays parallel to the optical axis will be perfectly focused to a point (the mirror is free of spherical aberration), no matter where they strike the mirror. However, this is only true if the rays are parallel to the axis of the parabola. When the incoming rays strike the mirror at an angle, individual rays are not reflected to the same point. When looking at a point that is not perfectly aligned with the optical axis, some of the incoming light from that point will strike the mirror at an angle. This results in an image that is not in the center of the field looking wedge-shaped. The further off-axis (or the greater the angle subtended by the point with the optical axis), the worse this effect is. This causes stars to appear to have a cometary coma, hence the name.>>
Art Neuendorffer

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Fred the Cat
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Re: APOD: Aurora Slathers up the Sky (2017 Jul 29)

Postby Fred the Cat » Sat Jul 29, 2017 2:21 pm

D’oh! The problems inherent to space photography. :bang: It’s amazing Hubble can deal with them let alone those on ISS. :thumb_up:
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Re: APOD: Aurora Slathers up the Sky (2017 Jul 29)

Postby A Really Bad Musician » Sat Jul 29, 2017 7:20 pm

Burrito Of Awesomeness would be an awesome name for a really lousy band.....


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