To experience the illusion: position yourself a comfortable distance from the screen and scroll down so that only the image
and no distracting text is visible, relaxing your eyes as you look "beyond" the two orbs as if focusing in the distance. The
images will seem to merge, with a third orb appearing between the two. Concentating on this "apparition orb" will bring it
and the background stars into crisp 3D focus!

If you have difficulty merging the two images, put your nose right up to the screen and you
will see the "apparition" image,
though you will not likely be able to bring it into crisp focus at this distance. Slowly back away while concentrating on
keeping the "third" image in view until you
are far enough away to be able to bring it into focus. Once you've "trained" your
eyes of what to look for, the illusion is easier to repeat.

How it works: Our brains tend to interpret data in the context of what is already most familiar. Thus when relative positions
between objects in otherwise identical left/right images are slightly altered, it is perceived as spatial displacement... 3D!
Shifting the entire background starfield of the right image to the left creates the illusion that  the moon is "floating above"
a  field of stars. Further manipluation of individual stars allows the starfield itself  to appear to be multi-dimensional.
Lunar Eclipse 08-Nov-2003