I found what looks like a "crystal ball" in a meteorological station in the Vlădeasa mountains (Romania). What is its purpose?

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    $\begingroup$ It's a high-tech version of the weather rock $\endgroup$
    – Mark
    Jan 8, 2017 at 20:36

1 Answer 1


It's a Campbell-Stokes sunshine recorder, used to record the times at which the sun is shining. It acts as a lens, focusing the sunlight onto a piece of card. If the sun is shining, the focused beam will burn a hole through the card at that point.

Here's a closer view of a sunshine recorder in Wendelstein, Bavaria: Sunshine recorder Source: Wikimedia Commons

And here's a used recording card with holes burned through it: Recording card Source: Wikimedia Commons

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    $\begingroup$ But beware of early morning frost on the glass sphere, which may diffuse the focus so that early sunshine is not recorded. $\endgroup$ Jan 11, 2017 at 9:03

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