Galileo's telescope: an anniversary

Galileo did not invent the telescope.
Rather, he realized the telescope's potential for astronomy.

In his own words:

About ten months ago a report reached my ears that a certain Fleming had constructed a spyglass by means of which visible objects, though very distant from the eye of the observer, were distinctly seen as if nearby... A few days later the report was confirmed to me in a letter from a noble Frenchman at Paris, Jacques Badovere, which caused me to apply myself wholeheartedly to inquire into the means by which I might arrive at the invention of a similar instrument. This I did shortly afterwards, my basis being the theory of refraction...
...
It would be superfluous to enumerate the number and importance of the advantages of such an instrument at sea as well as on land. But forsaking terrestrial observations, I turned to celestial ones...
["The Starry Messenger" (1610), Discoveries and Opinions of Galileo, Translated with and Introduction and Notes by Stillman Drake]

Galileo discovered the moon to be mountainous and cratered; Venus to have phases, like the moon; and Jupiter to have moons, in a system neatly analogous to the Copernican universe.
Galileo is a delightful read (via English translation... I lack the capacity to read him in his original Italian.)

Why Galileo just now?

This was suggested by a loyal reader (see comments below).

"The Starry Messenger" was published in 1610. In it, Galileo states that he learned of "a Fleming's" invention of the telescope "about ten months ago".
It is likely that Galileo constructed his telescope, based on the theory of refraction, in 1609.

2009, then, is the 400th anniversary of Galileo's "discovery" of the telescope - and the revolution in astronomy which followed.

A digression.
Galileo represents the experimental physicist par excellence. In addition to his telescopic observations of the heavens, Galileo also discovered, empirically, the basic laws of motion.
By rolling marbles down inclined planes, timing & measuring the descent, Galileo discovered the relationship between time, distance, velocity, and acceleration later implied by Newton's Laws.

Note: Time is a dimension that Galileo considered.
Just how did he measure time?
Recall - Galileo is perhaps most famous for noticing that a pendulum's cycle defines a more-or-less constant unit of time.
For calculus freaks: pendulum clocks work because

limit[t -> 0] sin(t)/t = 1.

Okay - back to the question:
Given his lack of a clock, how did Galileo measure time?
[I know the answer... or, more correctly, I know a plausible answer - not necessarily the true answer.]

... my original intent was to keep writing - to reveal Galileo's secret for measuring time without a clock...

But then I thought better of it.
Best to leave this puzzle for my loyal readers.
Please - if you've an idea, post a comment!

I'll reveal Galileo's secret (or at least, as previously stated, a plausible version of Galileo's secret) in a later post...

Sing a song!