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Dave W posed the question:
"who's how close to who when?"

Let's see... The Earth was at maximum distance from the Sun (aphelion) a couple of days ago. I guess that's out.

Lunar occultation tonight maybe? For those in most of North America, and beyond, the Moon will occult the star pi Scorpii tonight. The official IAU name for this star is now "Fang" (*). Here in southern New England, the disappearance behind the Moon's leading, dark limb occurs around 1am local time. At that time the Moon will be less than 10° high in the southwest. Reappearance will not be visible at all since the Moon will be below the horizon by then.

For navigation and surveying work, the time of an occultation can be recorded to nearest second (at least) visually. That's really the time of disappearance on the dark limb. The leading limb is dark for the first two weeks out of every lunar month, more like ten days in practice. Reappearance is much harder to time. A star peeking out near the bright lunar limb is barely visible, and if you're not looking at the exact spot, you might not notice it for 15 or 30 seconds.

The events article for this week at Sky & Telescope's website mentions this occultation and provides a link to lunar-occultations.com. I'm attaching their map below. S&T suggests using the locations list from the same site to determine the time at any observer's site. That's bad advice. The list of locations from lunar-occultations.com is antique (for web apps!) and misleading. Instead any decent sky simulation app, like Stellarium, will show local circumstances easily. A Stellarium tip: since this app represents stars as "glowing blobs" for aesthetic appeal, they do not "wink out" as they should when they reach the lunar limb. To find the exact time of the occultation, highlight the star (click on it). This will put a little reticle --a circle-- on the star, and you can advance the time until that circle is exactly split on the Moon's limb. Stellarium does not include any corrections for the mountains and valleys of the lunar limb, but it will get you within a some seconds of the true disappearance time.

Frank Reed

* The IAU-sanctioned name "Fang" comes from a Chinese star pattern. The IAU added a few western names to the official list in the first round of IAU names almost ten years ago. Recently many more have been added. It remains to be seen whether these will "catch on". Star names have no astronomical purpose, but they do carry some cultural weight. 

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