Hello Albert, et al
Alas, a dial such as the one you refer to won't work at all well at
such a low latitude. Spend a moment or two with your favorite sundial
program and you'll see why.
Best wishes,
Mac Oglesby
I assume there is a building or pole, or some such feature somewhere
already. It doesn't meet your original request, but maybe the
school would be interested in this type of dial:
http://home.iae.nl/users/ferdv/shadow1.htm
My understanding is that the ground doesn't have to be level, and
can even be varying, which is a plus. Also, it is an interactive
dial, and instructional.
Many thanks to Mac Oglesby for telling me about shadow planes. My
own understanding of sundials improved a lot after I started
thinking in terms of shadow planes as opposed to "rays" coming from
the Sun. (I'm still new to this.)
Albert Franco
"Frans W. Maes" <[EMAIL PROTECTED]> wrote:
Hi Douglas & all,
It doesn't obey the initial conditions, but maybe a play-object is allowed
in a playground. How about a horizontal bar, on which children may turn
somersaults etc.? It can double as a sundial: let the bar just tilt 2 deg (3
cm at 1.70 m length), North end upward. Hour lines are almost parallel, as
this is almost a polar dial.
Regards,
Frans Maes
----- Original Message -----
From: "Douglas Hunt"
To:
Sent: 18 January, 2004 7:54 PM
Subject: A 'gnomon-less' sundial for locations near the Equator ?
>
> Can any of our Mailing-List experts suggest some horizontal sundial design
> suitable for locations almost on the Equator, (actually 2 Degrees North) ?
>
> We have been contacted by a school in Singapore, who would like to install
> a large playground sundial - BUT ideally having nothing above ground-level
> to cause any 'accidents', or increase the cost/complexity of their layout.
> They want to avoid a 'gnomon' obstructing vehicles in the playground area.
>
> They had initially thought of using a traditional "analemmatic", but those
> are not really suited to locations within the 'tropics' (because the Hour-
> markers will interfere with the central Date-scale). We recommended using
> a 'door-frame polar' design, as being the most popular for schools near to
> the Equator (i.e., two upright supports with a near-horizontal North/South
> cross-piece, the shadow of which tells time on Hour-lines painted on their
> playground) - but they prefer an entire layout on the ground, if possible.
>
> I will be very grateful for any suggestions, as to whether there is a type
> of sundial which could be installed at a nea! r-Equator location
- and which
> does not need a 'gnomon' (apart from maybe a person!), above ground-level.
>
> Douglas Hunt.
>
> --
>
> "MODERN SUNCLOCKS" - 'Human Sundials', using YOUR OWN SHADOW to tell time.
>
> Looking for a useful, decorative, yet UNIQUE feature ? - you've found it !
> For further details and photographs, see our Website at: www.sunclocks.com
>
> Mail Address: 1 Love Street, Kilwinning, Ayrshire, Scotland, KA13 7LQ, UK.
> Tel & Fax (UK): 01294 552250. International Tel & Fax: + 44 1294 552250.
> E-mails to: [EMAIL PROTECTED] OR [EMAIL PROTECTED]
> -
>
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