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In the "small world" theme, just now I was looking up stats on inferior conjunctions of Venus since there's one coming up on August 13 at about 11h UT. I found a nice old article by Jean Meeus listing details on these Venus conjunctions for over fifty years into the future (and with some comments on those future transits of Venus in 2004 and 2012, too). That's over fifty years into the future from the date of publication in the Journal of the British Astronomical Association ...in 1971. And from 1971, the very last conjunction listed, half a century in the future is 13 August 2023 at 11h UT. Spot on, of course. :)

In the section describing the calculation methodology, he says he looked at the conjunctions by longitude (ecliptic longitude) which would be quite close to the minimum angular separation, and he notes that it's fair to ignore the ecliptic latitude of the Sun since it never exceeds 1.1". That should sound familiar! It's actually overkill for this article, and I have the feeling he's just bringing up something that intrigues him and probably for the same reason that we have been looking at it in the past few days.

I was looking into these Venus conjunctions getting ready to suggest to everyone that we have a few months coming up with great opportunities for daytime Venus sights. Yesterday, I caught Venus in binoculars just a few minutes after its meridian passage, but I couldn't yet see it naked eye. That will be significantly easier in a few weeks. With the exception of three to four weeks center on August 13, Venus will be relatively easy to shoot in daylight, and Venus and the Sun will allow fairly easy two-body fixes all day long, including my favorites: LAN for latitude plus simultaneous Venus for longitude (quick calculation, no plotting needed) and similarly Venus at meridian passage for latitude and the Sun for longitude (also quick calculation, no plotting). 

There's also an interesting observation challenge on the days right around inferior conjunction. Can you see Venus in daylight (with a telescope!) every day as it passes through between the Sun and the Earth? The exceedingly slim crescent of the planet may extend out beyond 180° from refraction through the atmosphere, and it will change orientation dramatically each day.

Finally, look at the pattern. Venus and Earth mutual events display a very nice eight-year repeating pattern. Meeus discusses this "well-known periodicity" in the article. This summer's inferior conjunction is a close match for the one in 2015, 2007, 1999, etc., and it will be repeated almost perfectly eight years from now but about two days and eight hours earlier on the calendar.

Frank Reed

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