+- +-

Advertisement

Copyright Notice

All photographs and content posted by members are to be considered copyrighted by their respective owners and may not be used for any purposes, commercial or otherwise, without permission.

Author Topic: Moon Illusion  (Read 2835 times)  

Offline Sotol Vista

  • Golden Eagle
  • Mountain Lion
  • *
  • Posts: 1339
    • My Big Bend Photos
Moon Illusion
« on: January 02, 2007, 06:34:12 PM »
Since the moon has been in the off topic scene lately, I thought I would share this bit of info.

Im sure yall have seen the moon rise when its full and it looks really HUGE, then a few hours later it looks much smaller, then again when it sets it looks huge again. Many call this the "moon illusion" so we will just stick with that for now. (you can Google "moon illusion" to read more on it if you are pretty board).

the "moon illusion" has been argued for a long time as to what the cause is and why it looks much larger at the horizon than directly overhead. As far as I know a definite answer has not been decided on. But there are several good theories and each make their valid points as to why this happens. Im not smart enough to decide which is correct.

one problem with the moon illusion is when photographing the full moon just after it rises, and then again after its been up several hours, it is the same size on film (or your digital photo).  This is one of the things that is in debate as to why this is.

here are 2 shots I took back in June 2006 and I stacked one over top of another to show that the camera captures basically the same size object.

both shots were using the Canon 20D, and the sigma 50-500 @ 500mm. one shot was when the moon was fully above the horizon but still very close to it. the second shot was several hours later when the moon was well above the horizon.

now when I took these shots the moon on the horizon it did look much larger than it did higher in the sky.





James
everything is better with bacon!!!

http://jamesb.smugmug.com/BigBendNationalPark/

Offline Casa Grande

  • Site Founder
  • Administrator
  • Mountain Lion
  • *
  • Posts: 4897
  • Passionate BIBEr Since 1991
    • Virtual Big Bend
Re: Moon Illusion
« Reply #1 on: January 02, 2007, 07:53:04 PM »
Quote from: "jamesb"


the "moon illusion" has been argued for a long time as to what the cause is and why it looks much larger at the horizon than directly overhead. As far as I know a definite answer has not been decided on. But there are several good theories and each make their valid points as to why this happens. Im not smart enough to decide which is correct.

James


i always thought it had something to do with the lighting angling off the atmosphere like in a pool of water.  neat experiment.

Offline Bobcat

  • Mountain Lion
  • *
  • Posts: 1471
Moon Illusion
« Reply #2 on: January 02, 2007, 08:53:27 PM »
That really is puzzling. I'm going to have to look into this one.
Location Location Location

Online tjavery

  • Golden Eagle
  • Mountain Lion
  • *
  • Posts: 1249
  • foto nut
    • http://www.texbrick.com/photo/proj_big_bend
Moon Illusion
« Reply #3 on: January 02, 2007, 09:12:27 PM »
That's pretty interesting!
best regards,
TJ Avery
Big Bend Photo Project: http://www.thomasjavery.com/proj_big_bend
Photo blog: http://www.thomasjavery.com/blog

Offline jeffblaylock

  • Horned Frog
  • Golden Eagle
  • Mountain Lion
  • *
  • Posts: 2225
  • I'd rather be on the South Rim
    • http://www.jeffblaylock.com
Moon Illusion
« Reply #4 on: January 02, 2007, 10:56:18 PM »
I've done a similar experiment and found the same results. I believe the eye perceives the moon (or sun) as being larger near the horizon because it interprets its size relative to the foreground objects on the horizon. Once it's up in the sky, the brain has nothing to compare it to, so it looks smaller up there all by itself. Just my theory, totally not borne out by any scientific facts ....
Jeff Blaylock
www.jeffblaylock.com

"We'll be back, someday soon. We will return, someday, and when we do the gritty
splendor and the complicated grandeur of Big Bend will still be here. Waiting for us."--Ed Abbey

Offline Bobcat

  • Mountain Lion
  • *
  • Posts: 1471
Moon Illusion
« Reply #5 on: January 03, 2007, 10:56:00 AM »
I think this pretty much explains the illusion(the Ponzo Effect that is):
http://www.unmuseum.org/exmoon.htm
Location Location Location

Offline Bobcat

  • Mountain Lion
  • *
  • Posts: 1471
Moon Illusion
« Reply #6 on: January 03, 2007, 09:56:46 PM »
Location Location Location

 

Advertisement

Looking to sell timeshare you no longer use? There are lots of potential buyers world wide interested in buying Timeshare resales and adventure locations like these are very popular to vacationers.

Advertisement