Moonrise over Seattle - a moon question answered

Sparks

This was todays Astronomy Picture of the Day. Apart from being a magnificent photograph, it also shows proof of something interesting - that the moon's apparent difference in size when close to the horizon is purely an optical illusion caused by our eyes or visual cortex, rather than some interesting optical process in the atmosphere, as has been suggested once or twice...

amen

moons size when low on the horizon is due to bending of lighr rays
I used to know the proof but can;t remember I'll try and look it up

Sparks

Amen, the whole point of that photo is to show that it isn't due to any actual physical effect, but is an artifact of how we process visual information.

Redshift

Sparks, do you have an article or a write up on this theory as I would be most interested in reading it. From looking at the photo I guess the photographer used some sort of filter for most of the exposure time. The thing that makes me belive that the photo is not real is that the few stars and planets visible should be also visible in the same way the moon is but they are actually only visible as a single point of light.

Nice photo though.


Ryan

Sparks

Originally posted by Redshift
Sparks, do you have an article or a write up on this theory as I would be most interested in reading it.

Try The Moon Illusion.

From looking at the photo I guess the photographer used some sort of filter for most of the exposure time.

No, just the atmosphere.

The thing that makes me belive that the photo is not real is that the few stars and planets visible should be also visible in the same way the moon is but they are actually only visible as a single point of light.

<barrrrrrrrrrrrp!>
This is the same fallacy as the "well the apollo photos were faked 'cos you can't see the stars in the photos of the moon" one
The reason you only see one "star" (I'm rather sure it's actually venus) is that the exposure time was so fast for the first 20-something shots, and then the last one was longer to bring up the city lights - which leads to the last moon image being so bright.



Nice photo though.


Ryan [/B][/QUOTE]

albertw

Originally posted by Redshift
From looking at the photo I guess the photographer used some sort of filter for most of the exposure time. The thing that makes me belive that the photo is not real is that the few stars and planets visible should be also visible in the same way the moon is but they are actually only visible as a single point of light.

The `faint` moons are just shorter exposure images, no need for a filter. Few stars are visible in the bright moon image as the brightnes of the moon swamps them out, plus its a bit cloudy.

All you need to do then is stack the images together to get the final image. Its fairly easy to do especially with digital cameras.

Cheers,
~Al
--
www.irishastronomy.org/boards

Redshift

Thanks, Sparks and albert that explains it.:)