Crescent Moon 1/7/14

[Bisonhead]

Wow, did anyone else catch it at around 2230 to the west? Deep orange in colour, low so big. Very atmospheric indeed. I have certainly never seen anything like it.

My missuse asked what makes it that colour. I suggested a mix of position in relation to the sun and atmospheric particles distorting the colour due to its height in the sky. I am by no means an expert so fully expect a less fantasy approach.

Any further insights?

[amancalledrob]

When it's low in the sky, light from it travels through much more of the atmosphere. Red light has a longer wavelength and makes it through better than light at the blue end of the spectrum, which has a shorter wavelength and is scattered more easily by airborne dust

[Eric Mc]

It's red for the same reason we sometimes get red sunsets.

[Bisonhead]

amancalledrob said:

When it's low in the sky, light from it travels through much more of the atmosphere. Red light has a longer wavelength and makes it through better than light at the blue end of the spectrum, which has a shorter wavelength and is scattered more easily by airborne dust

Thanks for that. Good to know

[tapkaJohnD]

And that it was "big" is a well known moon illusion, seen when it is near the horizon. Nothing to do with atmospheric effects, but to how we see it when compared with ground objects in the same view and our perception of perspective.

JOhn

[ReaderScars]

tapkaJohnD said:

And that it was "big" is a well known moon illusion, seen when it is near the horizon. Nothing to do with atmospheric effects, but to how we see it when compared with ground objects in the same view and our perception of perspective.

JOhn

Bit difficult accepting that to be honest!

If the moon was overhead and the OP reaches out, puts his thumb up, it would cover the moon - and if his arm was out horizontally to compare the size of this 'enlarged' moon, his thumb would not cover the larger moon.

[jammy_basturd]

ReaderScars said:

Bit difficult accepting that to be honest!

If the moon was overhead and the OP reaches out, puts his thumb up, it would cover the moon - and if his arm was out horizontally to compare the size of this 'enlarged' moon, his thumb would not cover the larger moon.

Are you suggesting the moon grows bigger relative to the Earth's rotational position?

[Bisonhead]

jammy_basturd said:

Are you suggesting the moon grows bigger relative to the Earth's rotational position?

Is it not to do with a 'lensing' effect of a thicker atmosphere in relation to the position of the moon to the observer?

[ReaderScars]

jammy_basturd said:

Are you suggesting the moon grows bigger relative to the Earth's rotational position?

Come on - I'm clearly not suggesting anything like that!

I am stating the fact that, the area of retina covered by the moon's image differs according to it's azimuth.

There is no single theory which proves out the points put forward that the moon image remains the same size and that it's our preception of it which changes due to earth bound objects - as stated on the NASA science site:

http://science.nasa.gov/science-news/science-at-na...

"Some researchers believe that the Moon Illusion is Ponzo's Illusion, with trees and houses playing the role of Ponzo's converging lines. Foreground objects trick your brain into thinking the Moon is bigger than it really is"

Some researchers believe - emphasized for emphasis!

"But there's a problem: Airline pilots flying at very high altitudes sometimes experience the Moon Illusion without any objects in the foreground. What tricks their eyes?"

"Maybe it's the shape of the sky."

Etc, etc. At the foot of that NASA page there are plenty of links to equally sound theories regarding the phenomenon.

[Eric Mc]

Back in the 1970s, a whole episode of the Sky at Night was devoted to the moon illusion and they confirmed just that - it was an illusion.

[tapkaJohnD]

ReaderScars said:

I am stating the fact that, the area of retina covered by the moon's image differs according to it's azimuth.
.

Readerscars, Instead of telling us what you believe, go outside tonight and measure the diameter of the Moon, above and near the horizon. You will contradict yourself, as any astronomer will tell you.

ReaderScars said:

Some researchers believe - emphasized for emphasis!

You misunderstand. As you know there are a number of theories to explain this illusion. "Some researchers" favour one, others favour another. This is called science, the competition between theories, and that competition does not invalidate the observation that the Moon APPEARS bigger next to the horizon, but in fact is no bigger than it is at the zenith.

John