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[EMAIL PROTECTED] wrote:
>
> Hello!
>
> I have a problem that occupies me for a while now. It reminds me of
> sundials, so I am posting the next question to this mail-list looking for an
> advice. I would also appreciate any information about articles or books
> published on this specific problem.
>
> "In the room of known shape and dimensions, it is required to
> determine the area on the wall of known azimuth, where the sunlight that
> comes through the sunroof of known dimensions and position (latitude &
> longitude), will not hit the wall at any time during the year."
>
> I understand it is necessary to find out some kind of solar equation
> of motion, that would enable for the projections of beams through the
> one(picked) corner of the sunroof's opening (for the purpose of simplifying)
> to be calculated. All this on basis of lat&long of a sunroof's corner, and
> dimensions and azimuth of the wall. Or, to simplify it even more -- to
> determine the projections for extremal values of Sun's zenith (for each of
> 365 days, or some other, fewer interval) -- that would give the area COVERED
> by the sunlight -- then the solution is everything OUT OF IT. Of course, the
> quality of such approach would mostly depend on a value of azimuth of the
> wall.
>
> There are possibly so many different approaches to this, that I feel
> a little bit lost. So, any help would be very welcome at this moment: an
> advice, some useful literature or even practical help (on accuracy of input
> data and necessity of applying the GPS, for instance, having in mind the
> required accuracy for projections in range of milimeters!).
>
> That would be it. If you think you can help me, please feel free to
> e-mail me at: [EMAIL PROTECTED]
>
> Thanks!!!
Hi 'om',
Your problem can be solved by calculating sundials.
Assume you live at latitude 50 degrees.
The wall in the room is vertical (inclination 90 degrees) and it faces
20 degrees west of south. (declination 20 degrees).
Measure the perpendicular distance from one point of the sunroof to the
wall. These is the input of your dial you need.
Now calculate a sundial for this plane ( based on latitude, inclination,
declination and length of the gnomon) with at least date lines for the
solstices and draw it on your wall. Only on the part between the
solstices the sun can shine.
Does this for all the 4 corners of the sunroof.
A mathematical methode how to calculate a plane sundial is on my
homepage
http://www.iaehv.nl/users/ferdv/
Click English and than the page to compute sundials.
You also can use the sundial program 'zonwvlak', obtainable via NASS or
BSS, resp. North American and British Sundial Society.
Another methode is to make use of the so called Horizontoscoop.
This is an instrument, based on an Oughtred sundial, with a plexiglass
dome over it.
In the plexiglass all the surounding is reflected.
Holding this instrument on any point of the wall, you can directly see
if the sun can reach that point through the sunroof.
This instrument is available in Germany.
The last offer I have is of october 1996, DM 328.80.
I posses such an instrument over 13 years.
It is delivered with the Oughtred design for latitudes between 51 and 53
degrees.
For other latitudes, ask.
Also remember that the sunroof itself perhaps doesn't receive sunlight
all days in a year. Surrounding buildings and trees can cast shadow on
the roof.
This makes the problem a little more complicated.
In the horizontoscoop this is directly visible.
Best wishes,
Fer J. de Vries, Netherlands.
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