Dialing friends
The idea of
"mesh roofs" and {Snip:} "different mirrors in
multiple windows at multiple tiltings, coloring them
different colors by a dip in colored lacquer and
marking their spots with colored thumbtacks"
This reminds me of a comment my wife made to me after
I had stayed up a good part of the night working on my
dail, "At some point it becomes a folly."
I spent the next 2 nights doing the same thing.
Still looking for folly,
Mike
36.9151 : 121.3539
--- Edley McKnight <[EMAIL PROTECTED]> wrote:
> Hi Anselmo, Fer, Ceiling Dialists,
>
> This is a repeat of a message I sent earlier that
> bounced. My ISP sends my mail with one of three
> addresses depending on which site I'm logged into,
> so I changed my sundial address to this one:
> [EMAIL PROTECTED] Sorry if you receive more than
> one copy of this.
>
> It seems that one solution to a ceiling sundial,
> within the tropics, would
> be to make a mesh room, with mesh ceiling and walls,
> Enough sun could
> come through to strike the mirror and project a spot
> which could be seen
> on the mesh surface. colored twists of wire could
> be hung to mark these.
> Perhaps the mirror could be made somewhat larger
> with an X marked from
> corner to corner, thus allowing us to find the
> center of the light spot
> even if partly blocked. Since we, ourselves might
> create this room, the
> surface of the ceiling could be quite level, perhaps
> using the hose with
> water in it technique or a laser level.
>
> As a note: Perhaps false ceilings were invented to
> give us a flat
> ceiling for dials when the old ceiling was tilted or
> lumpy. <g>
>
> Or, as you suggest, we could mount different mirrors
> in multiple
> windows or at multiple tiltings, coloring them
> different colors by a dip
> in colored lacquer and marking their spots with
> colored paint or
> thumbtacks. It would surely be a colorful way to
> tell time. :-)
>
> Couldn't one mount a playhouse in a window and
> construct a ceiling dial on it's small ceiling?
> What a deal for miniaturists! ( It could solve the
> flatness problem )
>
> Yes, Fer's analysis is really splendid!!
>
> Edley
>
> Anselmo wrote:
> > Wow!
> >
> > The analysis of the limitations of polar
> ceiling sundials made by
> > Fer
> > de Vries is just splendid. Essentialy the problem
> is: if we move the
> > mirror inwards it could fall under the ceiling
> shadow and thus produce
> > no dot of light, and if we move it outwards the
> ray of light goes back
> > outside when the Sun is high, so, once again, we
> are in one of these
> > equilibrium-of-forces problem. In my opinion the
> worst limitation is the
> > one imposed by the size of the window, and I guess
> there are no general
> > solutions and we are bound to a trial-and-error
> balance analysis for
> > each case.
> >
> > Maybe we could have several non-overlapping
> mirrors, each one for every
> > case, but then our problem looses a lot of its
> simplicity.
> >
> > Anselmo PÈrez Serrada
> >
> > > Dialists,
> > >
> > > In my mind I wanted to make a try for a polar
> ceiling dial at latitude
> > > 52 degrees, mid Netherlands.
> > >
> > > In the attached picture you see the mirror M at
> a distance g from the
> > > ceiling. The polar pattern for this
> configuration is drawn below left
> > > and I want to have the hours 8 am - 4 pm on the
> dial, if possible. (
> > > no longitude correction
> > in
> > > this story )
> > >
> > > The line BC then is about the limit of the space
> I need on the
> > > ceiling, or with other words, the mirror should
> be inward the room
> > > over a distance AB.
> > >
> > > Let's now have a look if the sun will shine on
> the mirror all year at
> > noon.
> > > It's obvious that I need to look for the limits
> at summer solstice.
> > >
> > > It is seen that during the summer solstice the
> sun can't shine on the
> > mirror
> > > at all.
> > >
> > > The first change I need to make is to cut of the
> ceiling at the line
> > > PCQ
> > in
> > > which C is the intersection point of the summer
> ray and the ceilng.
> > >
> > > In the hourline pattern the hours before 10 am
> and after 2 pm will be
> > > cut
> > of
> > > too and the first conclusion is that at summer
> solstice the dial is
> > useable
> > > from about 10 am to 2 pm.
> > >
> > > However, there are more things to concider.
> > >
> > > In this configuration the mirror will catch the
> sun at summer solstice
> > only
> > > at noon.
> > > Shortly before and after noon the mirror is in
> the shade.
> > >
> > > To see this we need to imagine a vertical south
> facing dial through AM
> > with
> > > a (pin)gnomon of length AC.
> > > That pattern is drawn below at the right side.
> > >
> > > At noon the edge of the ceiling gives a line of
> shadow KL and the
> > > mirror just catches the sun. Before noon and
> after noon this line of
> > > shadow moves down ( to the right
> > in
> > > the drawing ) and the mirror won't catch the
> sun.
> > > It sounds strange, after noon the altitude of
> the sun decreases and
> > > also
> > the
> > > shadow on a south facing dial decreases.
> > > Yes, this is true and can be seen with the shape
> of the dateline for
> > > the summer solstice. Before and after noon this
> date line in going
> > > down. So at the summer solstice my dial only
> gives a "flash" at noon
> > > and no more.......
> > >
> > > The third problem to concider is the width of
> the window.
> > > Because the mirror is inside the room the azimut
> of the lines from
> > > mirror through the edges of the window also will
> give limitations For
> > > this an analemmatic dial or Oughtred dial could
> be of use to see what
> > > the limitations are.
> > >
> > > Who will show us the first real
> polar-mirror-ceiling dial?
> > > Who has an inclined ceiling, higher at the south
> end?
> > > Won't that be better?
> > >
> > > Fer.
> > >
> > > Fer J. de Vries
> > > [EMAIL PROTECTED]
> > > http://www.iae.nl/users/ferdv/
> > > Eindhoven, Netherlands
> > > lat. 51:30 N long. 5:30 E
> > >
> > >
> > >
> > >
> > >
> > >
> >
>
>
>
>
> --
>
>
>
=== message truncated ===
=====
Mike DeAmicis-Roberts
phone: 831-636-0454
email: [EMAIL PROTECTED]
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