"Lieber Herr Prof. Backhaus,
The horizontal sundial on Halde Hoheward with its obelisk as a shadow caster is optimally appropriate to perform our experiments on a large scale. We visited it on March 21rst and determined the actual value of the equation of time by observing exactly the time at which the shadow crossed the noon line (12:37:54 MEZ). With the exact longitude of the dial which is given on a display board (λ=7°10'11.5") we got eot=6m27s. (The exact value was 6m31s!)
|The oblisk and its shadow||just before noon||just after noon|
In case of sunny weather on April 24th, some of our partners will perform our measurements on a large scale.
|Registering the noon position of the shadow.
The line from north to south is already fixed.
|Noon results of April 2nd|
The first spring days at the beginning of April gave us the possibility of exercising and improving our procedures and of finding the exact northern direction. With our noon results of April 2nd which can be read in the right picture above (and knowing the eot and the sun's declination of that day), we determined our geographical position. Our result: φ=51.6°, λ=6.8°. (Our GPS states as the correct position: φ=51°27.839'=51.434°, λ=7°0.240'=7.00°.)
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