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The Campbell–Stokes recorder (sometimes called a Stokes sphere) is a kind of sunshine recorder. It was invented by John Francis Campbell in 1853 and modified in 1879 by Sir George Gabriel Stokes. The original design by Campbell consisted of a glass sphere set into a wooden bowl with the sun burning a trace on the bowl. Stokes's refinement was to make the housing out of metal and to have a card holder set behind the sphere.
The unit is designed to record the hours of bright sunshine which will burn a hole through the card.
This basic unit is still in use today with very little change. It is widely used outside the United States, where the Marvin sunshine recorder is generally the instrument used by the National Weather Service.
These are still being sold by Casella csa along with the cards.
The heart of the device is a 100 mm (4") diameter glass sphere that's of fine optical quality that acts as a lens to focus the energy from the Sun onto a replaceable card marked with hour lines.
The Campbell Stokes sunshine recorder is the cover photo for the book The Weather Observer's Handbook / Burt, Stephen Cambridge University Press
As received the latitude adjustment was set for 28.5 deg North. Not sure where, maybe a little south of San Antonio, TX.
The Eppley (Model 2) Precision Pyranometer, Model PSP covers 285 to 2800 nanometers and is a similar instrument.
Still made by Fairmount Weather Systems in the UK and they have the replacement cards for three seasons.
Fig 1 Left Front
Fig 2 Left Side (came with lat = 28.5 deg N.)
Fig 3 Front face three card positions shown
Estimated Card width:
Winter: 38mm, Equinox: 42 mm, Summer: 33mm
Fig 4 Back
As received the latitude adjustment was set for 28.5 deg North. Not sure where, maybe a little south of San Antonio, TX.
I'll be setting it to 39.1 deg North for my location.
It turns out that with the latitude adjustment bolt as it was the range on the degree scale was 0 to 33 deg, but I need 39.19 (if the scale is for latitude) or 50.8 deg (if the scale is for 90-Lat).
So the 7-1mm bolt was removed and then installed in the other hole that provides for 28 to 65 degrees.
Fig 5 Bottom of latitude arc showing the two pinch bolt positions. Note: a 0.120" dia pin is needed to turn the latitude pinch bolt. You can see it in the bottom of Fig 4 above.
As a first try I'll just cut them out of regular copy paper and see how they work.
Regular copy paper is crumples when installed. Maybe card stock or some heavier paper would work better?
The official cards have been treated to they will not catch fire (maybe a 50-50 mixture of Alum and water?).
They are supposed to burn even in weak sun conditions (maybe the deep blue color?).
They also have a specification to not distort if saturated with water and then dried out.
Fig 6 First try at making card
Fig 7 After some Sun
Fig 10
Available from:
Fairmount Weather Systems in the UK
Fig 11
Astronomy
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Digital Photography 204: Studio Flash - triggers SkyScan like lightening
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TMQ-34 Meteorological Measuring Set -
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http://collections.rmg.co.uk/collections/objects/10929.html - they don't seem to know what it is.
Metcheck - MET-1603-D1 Cards for 0-40° Sunshine Recorder - (2014 - £100 for 380 cards total of Winter, Equinox and Summer cards)
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Page created 18 April 2014