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Mooning

The Buzz on Petau, Kopernik and Tyge

Dave North


As this part of the year drifts by (along with the all-too-common clouds) the first quarter (and earlier) moon slips higher and higher in the sky.

If you want a good look at the eastern half of the moon, you generally must wait until just after full Moon and set your sights on midnight or later.

But not now!

Because the early Moon is so high in the sky, some of these goodies are often seen in steady air just at sunset, even though the Moon has already begun to set.

I remember one May at Fremont Peak when I had my 12.5 set up next to Rich Neuschafer's then-newish AP180 and the air was dead calm at sunset ... we had incredible views of the Moon at roughly 45 degrees altitude, though some tree branches ran brief interference.

It was a great prelude to a dark sky night, and the air was steady enough to let even my 12.5-inch work to full advantage.

This kind of thing can happen any night this time of year, so don't waste that twilight: look at bright things and check for seeing!

That halcyon night at The Peak was particularly memorable for the great views of the Gang Of Four (my own name for the four similar, large and obvious craters that show up a few days into the lunar cycle. They are wonderfully named all: Langrenus, Vendelinus, Petavius and Furnerius).

I was especially enthralled (literally bubbling enthusiasm; it was truly a sickening spectacle for those present) about the complex rille structure in Petavius - which usually isn't all that complex.

Petavius is particularly friendly to any telescope, because it has one of the fattest rilles on the moon, and at the same time offers a well-defined shape and good detail in the walls.

In other words, it's interesting and easy to see.

But it has some hidden secrets: a couple of finer rills and other features that only show up in very good conditions.

We could see *everything.*

And if you want to see what's there, you should try and try again. One day you'll hit it. Especially late this month.

But early in just about everyone's lunar career, the Rille in Petavius will figure as one of the more memorable discoveries (whether I point it out or not, you'll eventually notice it: it's a real standout!)

Any telescope will do.

As to the hifalutin name Petavius, some folks might wonder why most of the things on the Moon are named after ancient Latins... well, they're not.

Petavius is named after a French Jesuit Cleric named Denis Petau, but it was stylish (if not even reasonable) for mid-era Europeans to "translate" their names into Latin - not an easy thing sometimes, as there wasn't any reasonable translation. In this case, the name Denis is thought to be a genetic drift of Dionysius, and Petau ended up Petavius somehow.

The same sort of thing happens right now when folks who don't come from an English-speaking country publish on the Web; they often translate their names using an alphabet (ours) that doesn't offer a good match for the sounds in their names - so it's often easier to just adopt a similar name from the English arsenal.

Of course, in those days, all scholarly works were in Latin. Now, the language of science, computer and otherwise, (as well as air traffic control) is English. So we see the same thing happening.

Petau was essentially a translator of Greek works, and a very good one. His deep knowledge of the subject led to the writing of histories that are still considered definitive today.

But why is this magnificent crater - one of the more striking on the Moon - assigned to a notable but otherwise obscure historian while some other far more solid contributors are essentially unmentioned, or assigned tiny, obscure craters?

Politics, of course!

Though he was slightly controversial in his interpretations, Petau stood in good with the Vatican, which was an almost unparalleled power in the 16th and 17th centuries (his time).

And if you wanted a Moon map published in those days, it was a good idea to stay tight with the Powers That Be (again, nothing has changed in that regard).

So that, mostly, is why when you look at the moon you hear tons of obscure Latin names rather than something that should sound a bit more familiar.

But it's not a completely grim picture.

You'll also hear Copernicus (actually a Polish guy named Kopernik), Kepler (his real name) and the curious Tycho - actually Tyge in his native Denmark (that part of which is now in Sweden).

What's so strange? It's his first name, not last! It would be like, oh, if Aldrin Crater were actually named "Buzz."

Can you think of another crater that's a famous first name?


Mail to: Dave North
Copyright © 2001 San Jose Astronomical Association
Last updated: July 19, 2007

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