May be not quite what you're after but I built 'one' based on info from
this web site:

http://weather.overflow.net.au/station/stevenson.html

Regards

Bob

http://www.hartsleap.com/weather

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I've been meaning to build one of these for some time but I'm still not
convinced that the relatively small volume won't still give rise to some
internal solar heating. How have you found it from this aspect?
Dave