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Thread: inferior conjunction of Venus

  1. #1
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    inferior conjunction of Venus

    When was this first observed where the person seeing it knew that it was Venus?

    Thanks

  2. #2
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    Could you be more specific, please? Humans have observed inferior conjunctions of Venus (or just-about-conjunctions) for millenia, well aware that Venus was, well, Venus.

    Do you have some particular issue in mind? Are you wondering about technology?

  3. #3
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    Thanks for the response.

    No I was wondering when this was first observed - can Venus be seen transiting the sun with the naked eye? If so then there is no real answer.!

  4. #4
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    A Transit is a little more selective an event than a simple inferior conjunction. Transits happen a couple times every few hundred years.
    I'm not aware of anyone recording that they had observed a transit of Venus before 1639. This writer thinks it might have been possible that an earlier observer saw one, so take a look.
    Forming opinions as we speak

  5. #5
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    Quote Originally Posted by Hans View Post
    No I was wondering when this was first observed - can Venus be seen transiting the sun with the naked eye?
    Sky and Telescope: Your Viewing Guide to the Transit of Venus(2012 May)

    A transit of Venus is a naked-eye event, meaning people with normal vision can see Venus's disk in front of the Sun without using binoculars or telescopes. (Learn how to safely view the transit.)
    0 1 1 0 1 0 0 1 1 0 0 1 0 1 1 0 1 0 0 1 0 1 1 0 0 1 1 0 1 0 0 1 1 0 0 1 0 1 1 0 0 1 1 0 1 0 0 1 0 1 1 0 1 0 0 1 1 0 0 1 0 1 1 0 ...
    [COLOR="#f9f9f9"]Testing... 1... 2... 3...[/COLOR]

  6. #6
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    The Babylonians recorded that they could visually track Venus until it got so close to the sun that the planet was rising or setting when the sun was less than about 6 degrees below the horizon, at which point it became lost in the sky brightness. This critical angle of the sun below the horizon was called the arcus visionis - if Venus was above the horizon when the sun was more than this arcus visionis below the horizon, Venus was visible; otherwise, not.
    Thing is, at favourable inferior conjunctions Venus can be almost 9 degrees from the sun - at these inferior conjunctions it can be picked out with the naked eye even when the sun is up, if you know where to look - see this paper recording observations during the favourable inferior conjunction of 1935, for instance. Daytime Venus spotting perhaps isn't something that ancient astronomers knew how to do - I don't know. But if it can be picked out with the naked eye with the sun above the horizon, it can surely be seen easily with the sun below the horizon.
    During the 1935 conjunction Venus was south of the sun, so for a northern hemisphere observer it set before the sun and rose after it, so it was neither a morning nor an evening star in the usual sense. But under different circumstances (for instance, passing north of the sun with an observer in the northern hemisphere) Venus can be a morning and evening star on the same day for a few days around its inferior conjunction. It depends on the observer's location, but in More Mathematical Astronomy Morsels, Jean Meeus calculated circumstances for such morning and evening star apparitions of Venus. They turn up in groups with an eight-year periodicity.

    So I would imagine that seeing Venus at inferior conjunction was going on long before we have any records. Beyond that, it depends on what you mean by "knowing it was Venus".

    Grant Hutchison
    Last edited by grant hutchison; 2017-Mar-20 at 12:27 AM.

  7. #7
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    Also: Venus is farthest from node in March and September, when the ecliptic is steep relative to horizon... save at poles. And there are few observers near poles. Otherwise... how would an observer on North Pole in March see Venus?

  8. #8
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    Thanks for the additional information and especially the Babylonian/Assyrian note!

  9. #9
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    Quote Originally Posted by chornedsnorkack View Post
    Also: Venus is farthest from node in March and September, when the ecliptic is steep relative to horizon... save at poles. And there are few observers near poles. Otherwise... how would an observer on North Pole in March see Venus?
    I'm sure you can simulate that easily enough with any of the free astronomy packages that are available.

    At latitudes higher than ~55 degrees it's possible to see Venus at local midnight. Since I live farther north than that, I have a hankering to do that once in my life. Perhaps I should start planning.

    Grant Hutchison

  10. #10
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    From five years ago, kinda cloudy. The other couple dots are sunspots, bigger than the earth, probably naked eye themselves, in the right conditions.

    Venus02.gif

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