While Willy is absolutely correct, the part about knowing and computing
for the shape of the dish is probably the real killer task.
This is an application where I would advocate the empirical approach:
Properly orient the dial face and style, then manually lay out points,
with a watch in hand. Plan ahead and (weather cooperating) do it on the
Equinox, and you can draw lines through the points to the dial center, at
the root of the style.
Dave
> Hi Andrew,
>
> you have to orient the disc to the south
> you have to decline the disc to a vertical position
> on a vertical and south oriented plane behind the disc you have to
> work out (virtually) the hour lines and date lines of a vertical
> south oriented nodal sundial - the node must be a part of the style
> of your sundial
> the lines from the node to 'specified points' of the plane sundial
> intersects the disc at the equivalent points on the disc ('specidied
> points' are the intersection points of the hour lines and date lines)
> to do this mathematically the shape of the disc must be known; is it
> a globe, a paraboloid, a hyperboloid ...?
>
> Willy Leenders
> Hasselt in Flanders (Belgium)
>
>
>
>
> Op 21-jun-07, om 19:27 heeft Andrew Corl het volgende geschreven:
>
>> Greetings all,
>>
>> Several months ago I bought a house and the previous owners left me
>> with one of those 12" diameter satellite dishes. I have no need or
>> want of Direct TV or satellite TV.
>>
>> I was sitting there thinking one day that it would make a really
>> nice direct south facing sundial. My house already faces a little
>> east of south anyway, and the location where the dish is gets
>> direct sunlight almost all year round.
>>
>> My questions is this: Do I need to make any adjustment in the
>> calculations of the hour lines for the shape of the dish? If so
>> what is the formula?
>>
>> I am going to install a simple style using a metal road about a
>> half inch in diameter. I want this sundial to tell solar time not
>> necessarily actual time. Though one day I may install an equation
>> of time underneat the dial .
>>
>> Boardwalk for $500? In 2007? Ha!
>> Play Monopoly Here and Now (it's updated for today's economy) at
>> Yahoo! Games.
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>>
>
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