"William Hamblen" wrote in message
news
On 2006-09-11, Thierry Thierry wrote:

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...

If I simulate the sky at that time, of Firenze, arcetri, we discover that
in
...
However it would have published his Siderius Nuncius in March 1610 (also
to
re-confirm).
....
The phases of Venus are in "Dialog Concerning the Two Chief
World Systems", which printed in 1632, and aren't in "Starry
Messenger", which was printed in 1610. There are fairly recent
English translations of both (Stillman & Van Helden).

I've got the Reston bio of Galileo around here somewhere. As
best as I remember, Galileo made a telescope sometime in 1609,
not long after news of the invention reached him.

Indeed. One more of my mistakes. The scope was indeed presented on August
21, 1609 (35 mm dia., 3x then 6x).
I had the Siderius but I mismatched what I read (there is long time ago).
Someone else confirmed me that there is no reference to venus in this
booklet, and the latinese text doesn't show any drawingf of venus
http://www.liberliber.it/biblioteca/...l/sidereus.htm
So Galileo had all the time to observe venus after March 1610 until his
presentation in March 1611.
Indeed, according to simulation, the crescent began to appear around the end
of 1610 and specially in dec 1610 (25") and february 1611 with a giant 57".
In sep 1610, when it seems have began to look at Venus, I think that it was
almost impossible for him to see the disk differently than a bright oval
spot, to confirm (he used a scope 3-8x only then about 30x) but venus showed
a diameter close to 12-15" only, 1/4 the one of jupiter that was already
quite small in his first scope.
So it is time for me to update my text and drawings at
http://www.astrosurf.org/lombry/galilee-hommage.htm

Thierry


Bud