Expert: Steven LJ Russo - 5/29/2006

Question
Hi Mr. Russo,

I want to photograph the full moon and have noticed that there are certain days of the month that the moon rises very large on the horizon.  How can I determine which night the moon will be the largest when it rises?  I am assuming it is closer to the earth on these nites which causes the large size.  

Thanks for your help.
Glenda

Answer
Glenda:

You will not be able to photograph that "larger" moon, because it is not actually larger.

It is something called "The Moon Illusion", and it is a perception problem caused by the brain and the eyes.

Constellations will also look larger when on the horizon.

It is actually the same size when on the horizon, as it is overhead!  Look at it on the horizon, and roll up a paper tube so that the Moon fits into it.  Schotc tape it shut.  Several hours later when the Moon is overhead, it will still fit inside the tube.

Or, to make the Moon look its real size whan it is on the horizon, bend over and look at it through your legs; in other words, upside-down.  The Moon will then look smaller!

Go to:

http://www.badastronomy.com/bad/misc/moonbig.html

for more information.  It's pretty complicated!

Steve