Hi all,
I was most grateful to have Martina's constructive feedback on
the strengths and weaknesses of my MultiDial as she sees it from a
teacher's angle. Her point that the dial in the jpeg I provided was for
a fixed latitude is well made and very easily addressed. Two attempts
to attach a small line drawing (48k), showing a simple modification,
attached to this message in the hope that it would be small enough to
evade the size filter have 'bounced'. Hopefully my text description
will be sufficient but .png files available on request.
Basically the vertical, horizontal and polar dials are delineated for
50° north and the base is hinged at the front edge with a simple curved
scale and clamping screw allowing any degree of tilt to be fixed up to
10°. This range will cover the British Isles from Cornwall to Orkney.
If the school is at e.g. 53° north then the north edge is raised 3°, the
horizontal plate is now parallel with the ground back at 50° north and
the dials 'think they are back home' and read true.
For awareness of seasonal differences in the Sun's cycles I've just
added declination lines and a nodus to the vertical dial although this
might also be on an additional 'face' without hourlines to reduce
possible visual clutter and confusion.
Removable/reversible 'faces', probably made from laminated card, with
BST and GMT numeration on opposite sides to slide into place would be
very easy.
For classroom direct teaching use I envisage dial plates of around 500mm
square or even more. The simplest of workshops could batch produce
these with little more than a circular saw, an edge planer and
semi-skilled labour for no more than £200 plus postage and probably far
less. Smaller ones for the children to handle and experiment with would
be equally easy.
I'm entirely in agreement with Jack Aubert about analemmatic dials for
teaching purposes (having made or contributed to four of them myself).
They are great fun and children love them but I'm not sure that they
understand very much at all about how or why they work. So where is the
potential for learning in that?
Tony Moss
P.S. Apologies if you've received this message twice - problems with
the message size filter.
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