"OG" wrote in message
...

Thierry wrote in message ...
Hello,

A question about historical truth.
It is said that Galileo discovered the phases of Venus phases in 1610.
OK.
It is also said that he invented his scope only in 1610
Two dates to be confirmed, and if possible in the month close...

Looks like the dates may be in error
Wikipedia

Not sure that wikipedia is a formal source of information
It will be not the first time that i correct data because references or
commentaries are not accurate, mix with rumor, etc.
I am agree that there are a lot of good things on wikipedia, I work on it as
well, but I don't consider it as an official source.
better to go to the museum of science of firenze, don't you think...

Thierry

"Based only on sketchy descriptions of the telescope, invented in the
Netherlands in 1608, Galileo made one with about 8x magnification, and
then made improved models up to about 20x. On August 25, 1609, he
demonstrated his first telescope to Venetian lawmakers."
http://en.wikipedia.org/wiki/Galileo#Astronomy

If I simulate the sky at that time, of Firenze, arcetri, we discover that
in Jan-April 1610 Venus was in the East, 10° over the horizon with 80%+
illuminated, thus very small, and at the end in the rays of sun. hard to
imagine that he observed it at that time. It nevertheless could have did
it.
On the other hand, at the autumn 1609 venus shows a fine crescent, and
was higher in the sky of the morning

Good work, and could well suggest that he observed Venus in Autumn 1609
rather than early in 1610.