Le 25 mai 2007, Ernie Wright a écrit :
[concerning http://www.perseus.gr/Astro-Lunar-Parallax.htm]

The situation looks something like this:

. * Selsey
. \
. \ -------- to the Moon
. \
. * Athens

The base we should be using,

. * Selsey ....... |
. |
. | -------- to the Moon
. |
. * Athens ... |


When I did this, I got a length factor of 0.928. Multiplying this by the
chord length distance between Athens and Selsey (2356 km) gives a triangle
base of 2186 km. Using your (probably more careful than mine) estimate of
the parallax angle, 1113.6", yields a distance estimate of 404,897 km, for
an error of only a little more than 2%. That's pretty cool!

Well, actually, the 395,520 km Anthony gave is the geocentric distance
of the Moon, i.e. the distance from the center of the Earth to the
center of the Moon. In geocentric coordinates, the Moon is a little
closer. My ephemeris program tells me the real distance of the Moon from
Athens is 391,741 km, so that the error is around 3.4 %. That's still
cool, however ;-)