Starship Asterisk*

neufer wrote:A vertical polarizer helps us to see other planets during the day (as well as circumhorizontal arcs) by cutting out singularly scattered blue Rayleigh scattering.

grump wrote:

atoptics wrote:This is not an iridescent cloud nor are water droplets responsible. It is a halo, a circumhorizon arc (http://www.atoptics.co.uk/halo/cha2.htm) produced by refraction in hexagonal plate shaped ice crystals in cirrus. Note the structure parallel to the horizon and the structured gradation of color from red at the top through green to blue. Both are characteristic of the halo.

The explanation of the apod says that the photo was taken using a polarising lens. Would the colours appear if it was not polarised?

atoptics wrote:This is not an iridescent cloud nor are water droplets responsible. It is a halo, a circumhorizon arc (http://www.atoptics.co.uk/halo/cha2.htm) produced by refraction in hexagonal plate shaped ice crystals in cirrus. Note the structure parallel to the horizon and the structured gradation of color from red at the top through green to blue. Both are characteristic of the halo.

Les Cowley
Atmospheric Optics - http://www.atoptics.co.uk

BMAONE23 wrote:

Karthik wrote:Any idea what is that bright object near the top of the image; the one just above what looks like a contrail? Perhaps an artifact?

I would say you have 1 of 4 choices

Choice 1) The planet Venus can appear this bright in the daytime sky especially through a polarized lens
(but venus is too near the sun to be visible during the day)
Choice 2) The ISS is slightly brighter than Venus now and is also visible in the day time skies.
Choice 3) a mylar balloon reflecting sunlight
Choice 4) most likely a bad pixel on the ccd sensor in the camera.

Dr. Skeptic wrote:Looking at the "full view" there is a similar anomaly (not as bright) dead center of the picture just under the cloud.

craterchains wrote:
mmmm k, This new forum style and layout are very poor IMHO, the old one was quite adequate. Why change it?

Andy Wade wrote:

craterchains wrote:This new forum stinks, , , , , , , , , , , , , , , , , , ,


Anyone else notice that these odd rainbow effects are VERY RECENT ? ? ?

Like in the past decade ? ? ? ? ? ? ? ?

Yer FUNNY ! ! ! ! ! ! ! ! ! !~

The forum stinks? Funny, I can't smell anything.
Say what you mean for goodness sake, that way people can understand you better.

Karthik wrote:

Dr. Skeptic wrote:

Karthik wrote:Any idea what is that bright object near the top of the image; the one just above what looks like a contrail? Perhaps an artifact?

Thanks

Look! It's a bird ... It's a plane ... No its Sup ... Aww, its just a plane's vapor trail .

Actually, I was inquiring about the bright, round object above the vapor trail.

Thanks

craterchains wrote:This new forum stinks, , , , , , , , , , , , , , , , , , ,


Anyone else notice that these odd rainbow effects are VERY RECENT ? ? ?

Like in the past decade ? ? ? ? ? ? ? ?

Yer FUNNY ! ! ! ! ! ! ! ! ! !~

Karthik wrote:

Dr. Skeptic wrote:

Karthik wrote:Any idea what is that bright object near the top of the image; the one just above what looks like a contrail? Perhaps an artifact?

Thanks

Look! It's a bird ... It's a plane ... No its Sup ... Aww, its just a plane's vapor trail .

Actually, I was inquiring about the bright, round object above the vapor trail.

Thanks

Dr. Skeptic wrote:

Karthik wrote:Any idea what is that bright object near the top of the image; the one just above what looks like a contrail? Perhaps an artifact?

Thanks

Look! It's a bird ... It's a plane ... No its Sup ... Aww, its just a plane's vapor trail .

Karthik wrote:Any idea what is that bright object near the top of the image; the one just above what looks like a contrail? Perhaps an artifact?

Thanks

bystander wrote:Art, imo you missed the most spectacular one
APOD: 2003 October 14 - Iridescent Clouds Over Aiguille de la Tsa

atoptics wrote:This is not an iridescent cloud nor are water droplets responsible. It is a halo, a circumhorizon arc (http://www.atoptics.co.uk/halo/cha2.htm) produced by refraction in hexagonal plate shaped ice crystals in cirrus. Note the structure parallel to the horizon and the structured gradation of color from red at the top through green to blue. Both are characteristic of the halo.

atoptics wrote:This is not an iridescent cloud nor are water droplets responsible. It is a halo, a circumhorizon arc (http://www.atoptics.co.uk/halo/cha2.htm) produced by refraction in hexagonal plate shaped ice crystals in cirrus. Note the structure parallel to the horizon and the structured gradation of color from red at the top through green to blue. Both are characteristic of the halo.

http://en.wikipedia.org/wiki/Circumhorizontal_arc wrote:
<<A circumhorizontal arc (also popularly called fire rainbow) is a rare optical phenomenon. In order to be observed, the sun must be high in the sky, at an elevation of [46°] or more, and can only occur in the presence of cirrus clouds. As a result it cannot be observed at locations north of [the Arctic Circle] or south of [the Antarctic Circle], although occasionally at higher latitudes from mountains. In areas of Northern Europe it can only be observed around the time of the Summer solstice. If cloud conditions are right it is seen along the horizon on the same side of the sky as the sun.

The arc is formed as light rays enter the [near] horizontally-oriented flat hexagon crystals through a [near] vertical side face and exit through the [near] horizontal bottom face. It is the 90° inclination that produces the well-separated rainbow-like colours and, if the crystal alignment is just right, makes the entire cirrus cloud appear to shine like an undulating rainbow.

Although quite rare, it is not the rarest of all natural phenomenon. The Kern arc and Lowitz arc are even rarer.

A circumhorizontal arc can be confused with an infralateral arc when the sun is high in the sky; the former is always oriented horizontally whereas the latter is oriented as a section of a rainbow, e.g. as an arc stretching upwards from the horizon.>>