Continued from last post but one

After this observation, the haze closed in again and no observation was possible for a while. When the sky cleared again, the sunspot had moved. Moved much further in an hour or so than a sunspot ordinarily moved in a day, but just about as much as the planet Mercury would have moved.

To understand what Gassendi was expecting to see, we must cast our minds back some 1500-odd years before Gassendi, to about the year 150 AD. At that time, the astronomer we know as Claudius Ptolemy published a book which came to be known by the name Almagest, from an Arabic expression meaning the greatest, although Ptolemy himself modestly called it simply a Mathematical Treatise. By whatever name, the book was a set of mathematical procedures for predicting the future location of planets in the sky based on observations of their past locations. This was a difficult task, since the motion of the planets is strangely irregular, or so it must have seemed to the ancient Greek astronomers.

I saw the Wolverine movie for nothing

Explanation:
My Friendly Local Comic Book Store has been running a promotion all summer long that if you brought in ticket stubs from a list of 7 or 8 movies you could get in a drawing for a chance at 2 movie tickets a week for a year.  One of the movies was Wolverine, which I didn't particularly want to see. But I saw it anyway for the chance at the tickets.
They held the drawing this evening, and I didn't win.
Oddly, however, it still cheered me up to clap for the guy who did win, although probably not as much as winning around $1200 worth of movie tickets would have!

One post in every calendar year, that's my motto.

And so far it hasn't steered me wrong, as Theophile Escargot said in a different context.

Paris. November 7, 1631. Pierre Gassendi has been watching the sun for two days, now, hoping to see something that no one in the history of the world has ever before seen: the passage of the planet Mercury across the face of the sun, a transit of Mercury.
Not that this has never happened before. In fact, it happens about 13 times every century, at irregular intervals. But no one before Gassendi has had both the tools and foreknowledge to observe the transit.
The foreknowledge is courtesy of the recently deceased German astronomer Johannes Kepler, who four years earlier in 1627 had published his Rudolphine Tables, the most accurate astronomical tables computed up to that time (all calculations done by hand, of course) and a year before, in 1630, had published an "Admonition" pointing out to Europe's astronomers that a transit of Mercury was predicted for November 7th, and advising that they watch for it, cautiously suggesting that they watch from November 6th to the 8th in case of errors in his observations or computations. Gassendi, even more cautious, decided to start watching on the 5th.