How to calculate conjunctions of 2 planets

  • So, the recent conjunction of Jupiter and Venus seems to have spawned lots of excitement over this "rare" event. But what I can't figure out, is exactly how rare it is. And I've seen such conflicting claims and calculations that I figured I'd better calculate it myself. The only problem is I'm no astronomer. So, does anyone know of a program that can calculate all the conjunctions between a date range that are within a degree of each other? Or does smart person know how to calculate it manually? :)
    I have a program called Stellerium which I've been using to view the various conjunctions that people have mentioned. I don't know if I can use it in the way I need it though. Any help? :)
    Thanks may be helpful, as might my (which simply combines SKYCALs for various years).

    Based on I believe part of the excitement is due to the triple conjunction between Jupiter, Venus, and Regulus. Since Venus completes a tour of the Zodiac in less than a year, and Jupiter doesn't move that fast, Jupiter and Venus conjunct yearly (in terms of ecliptic longitude at least) may or may not be helpful: apparently, the desire to compute conjunctions goes back to ancient times.

    The "methodology" section of my answer to may or may not be helpful.

  • The PyEphem library allows you to create Python scripts that could calculate any conjunction you want (and many other things besides that).

    Here's a script that already does that:

    Here's the result of running that script now:

    Notable event: extremely close conjunction between Jupiter and Venus in 2016:

    Conjunction of Venus and Jupiter lasts from 2016/8/25 to 2016/8/31.
    Venus and Jupiter are closest on 2016/8/28 (0.1 deg).

    Which is interesting because most sites reporting on this don't mention the 2016 conjuction and say we won't see anything like it for another 10 years or more. (It varies drastically by article)

    AdamsMasters, I don't have enough reputation to answer your comment outside of an answer so well, that's because it'll be very low when it gets dark enough to see. It should be visible to the naked eye for maybe literally 5 minutes between mid-twilight and it getting too low to see, but only if the sky isn't very hazy. However, this is from midnorthern latitudes. The Southern hemisphere should see that easily. A 6 to 9 thousand foot elevation with a low western horizon would be better than sea level. A telescope or binoculars would also make it easier to see as long as you can aim.

    It will be difficult to see unless you're free of surrounding buildings and trees. At the time of the sunset, they will be only 11 deg above horizon. That's only half the altitude of the conjunction this year at sunset. But if you have an open, flat field on the western side of town, you'll be able to observe that conjunction just fine.

    There's another Venus-Jupiter conjunction of 25 Oct 2015 that I don't think is mentioned on the pastebin page above?

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Content dated before 7/24/2021 11:53 AM

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