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The Campbell-Stokes Sunshine Recorder
Penny

Imeundwa na

Penny

23. Septemba 2026DK
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The Campbell-Stokes Sunshine Recorder

John Francis Campbell put a glass sphere in a wooden bowl in 1853 and let the focused sun char a track across it as the earth turned. George Gabriel Stokes replaced the bowl with a metal frame holding a replaceable paper card in 1879, and the design has not needed to change since. It is the only instrument in this batch with no moving parts and no scale to read. The sphere focuses sunlight to a point; the point sweeps along the card as the sun moves; where the sun was bright enough it burns, and where cloud intervened it does not. At the end of the day the card IS the record — a physical trace of the whole day's sunshine. There is a warning built into the object. A glass sphere in your garden focuses sunlight to a spot hot enough to set fire to dry material, and it does it whether or not you are paying attention.
Juu
2 days

Maagizo

1

Get a solid sphere, and respect it

Use a solid glass sphere of 75 to 100 mm diameter. From the moment you own it, treat it as a fire source. A 90 mm sphere concentrates sunlight roughly a thousandfold. Left on a windowsill it will scorch a curtain, a carpet or a bench top, and it has started house fires. Keep it covered whenever it is not mounted in the instrument, and site the instrument where its focus can only ever fall on the card and the metal frame — never on wood, thatch, decking or dry grass.

Vifaa kwa hatua hii:

Tufe gumu la kiooTufe gumu la kioo1 kipande
2

Make the bowl at the right radius

The card must sit exactly at the sphere's focal surface, which for a solid sphere of refractive index about 1.5 lies roughly half a radius beyond its surface — so the bowl's radius is about 1.5 times the sphere's radius. Work it out for your own sphere, then check it in sunlight before you build the frame: hold a card at various distances until the burn is a sharp point rather than a smear. A bowl a few millimetres out gives a broad scorch that cannot be read to the nearest tenth of an hour.

Vifaa kwa hatua hii:

Bati la mbao za kubandikaBati la mbao za kubandika1 karatasi

Zana zinazohitajika:

Msumeno wa mkonoMsumeno wa mkono
Sandarusi (karatasi ya kusugua)Sandarusi (karatasi ya kusugua)
RulaRula
3

Set the axis to your latitude and point it at true north

Tilt the bowl's axis so it is parallel to the earth's axis — that means an elevation equal to your latitude — and align it on TRUE north, not magnetic. Aligned this way, the sun's focus sweeps along the card at a constant rate all day and all year, so equal lengths of burn mean equal times. Get the alignment wrong and the time scale stretches and squeezes through the day. Find true north from the sun at local noon, or correct your compass for the local magnetic declination.

Vifaa kwa hatua hii:

Kigingi cha mbaoKigingi cha mbao2 vipande
Misumari iliyofunikwa zinkiMisumari iliyofunikwa zinki20 vipande

Zana zinazohitajika:

DiraDira
Nyundo yenye kuchaNyundo yenye kucha
4

Use the right card, and change it daily

Use a stiff, uncoated card marked with hour lines. Fit it before sunrise and remove it after sunset, every day, and write the date on it immediately. The standard uses three card shapes through the year — long curved cards for summer, short ones for winter — because the sun's track across the bowl moves with the seasons. Glossy or coated card does not char cleanly; plain matt card does. An unmarked, undated card is an abstract drawing within a week.

Vifaa kwa hatua hii:

Karatasi ngumuKaratasi ngumu40 vipande
Karatasi ya picha (multigrade)Karatasi ya picha (multigrade)1 paketi
5

Read the burn as duration, not intensity

Measure the total LENGTH of burnt track against the hour lines and add the segments. Gaps are cloud. This instrument measures bright-sunshine DURATION and nothing else. A deep, wide burn and a faint one both count as sunshine, so it cannot tell you how much energy arrived — for that you need a pyranometer. Knowing precisely which question your instrument answers is worth more than a more expensive instrument answering a question you did not ask.

Zana zinazohitajika:

RulaRula
6

Focus, threshold and what the card can resolve

Inapakia daftari la Jupyter…

Zana zinazohitajika:

RulaRula
7

Site it where nothing shades it and nothing burns

Mount it clear of anything that casts a shadow between sunrise and sunset — especially low winter sun, which reaches under obstacles that clear the summer sun entirely. Then walk round it at several times of day and check where the focus lands when the card is absent or has burnt through. Metal or stone beneath, always. This is the only instrument in this batch that can burn your shed down, and it will do it on the one sunny afternoon you forgot to fit a card.

Vifaa kwa hatua hii:

Karatasi ya AluminiKaratasi ya Alumini1 rolii

Zana zinazohitajika:

DiraDira

Vifaa

7

Zana Zinazohitajika

5

CC0 Umma Wote

Mchoro huu umetolewa chini ya CC0. Uko huru kunakili, kubadilisha, kusambaza, na kutumia kazi hii kwa madhumuni yoyote, bila kuomba ruhusa.

Saidia Mtengenezaji kwa kununua bidhaa kupitia Mchoro wao ambapo wanapata Kamisheni ya Mtengenezaji iliyowekwa na Wachuuzi, au unda marudio mapya ya Mchoro huu na uiunganishe kama kiungo katika Mchoro wako kuchangia mapato.

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