On Fri, Feb 24, 2017 at 1:04 PM, Steve Lelievre <
steve.lelievre.can...@gmail.com> wrote:
> Fellow sundiallers,
>
> I’m planning to make my next sundial from outdoor grade UV resistant
> plastic sheeting. These come in a range of colours and I want to choose one
> that works well for a sundial. Assuming I get the material grit-blasted or
> somehow treated so that it not shiny, and leaving aesthetic considerations
> aside, what light-related attributes should I be looking for?
>
> As anyone who has played with paper sundials knows, a white surface is
> hard to look at in full sun, even if non-shiny; black would not show any
> shadow.
Well, one would have to try it to be sure. Maybe black would work, because
nothing is *completely* absorbent. So why not start with the least
reflective color, black. ...and then try something else if the shadow
isn't visible.
I've never made a durable waterproof, windproof fixed-mounted outdoor
sundial, and so I'm just guessing, not speaking from experience. I made a
few pocket tablet-dials. My first one was typewriter-paper (computer-paper
now) on corrugated cardboard. Too bright to look at, of course. So, for the
rest of them, I got some brown construction-paper, but, instead of using
it, I just drew the hour-lines on the brown corrugated cardboard, instead
of pasting paper to it.
I, too, would be interested in hearing about the conventions, empirical
guidelines, or practical experience. I probably would have asked that
question sooner or later.
Yes, I've heard the color-attributes referred to as hue, saturation, and
brilliance. I'm sure that luminosity means the same as brilliance. Maybe
"brilliance" is better, because it doesn't carry any implication of the
object being a *source*.
I'm sure that brilliance is important, and probably is the most important
attribute.
It seems to me that I once read that brown is a low-brilliance
orange-yellow mix.
Hue could matter if some hues, wavelengths, are more damaging, irritating
or annoying than others. Of course the lower the saturation, the more
grayish, the more nearly the reflected light is an equal mixture of the
visible-light wavelengths. So, if some hues are more desirable than others,
then low saturation, grayish-ness, wouldn't serve any purpose.
We hear that, among the visible colors, blue is less desirable to look at a
lot of. Maybe partly because of its own effect, and partly because it's
nearer to the uv end of the spectrum. Yellow is the complement of blue. And
red and orange are at the opposite end of the visible spectrum from blue.
So, low brilliance, probably preferably high saturation (less grayish),
yellow orange or red?
I think that means brown, but it was a long time ago when I read about it.
If trying brown, might as well start with dark brown.
If brown isn't available, then maybe dark tan. If that isn't available,
then maybe dark red or dark orange (or maybe "dark orange" is the same as
brown or tan)?
I don't claim to have the answer to that question--just a few guesses. No
doubt someone will be able to genuinely answer the question.
Will this be a horizontal sundial, or a higher-mounted sundial intended to
be visible from farther away, for visibility to neighbors or passers-by who
aren't near enough to look down at it?
The translucency of the materials you speak of could be helpful if it's to
be viewed at a distance, because a translucent flat dial can be read from
all directions; and, if it has a gnomon on each side, then it has a shadow
regardless of which side of it the sun is on.
An equatorial flat dial has the advantage that its construction-principle
is the most immediately-obvious to all neighbors and passers-by. Unless
translucent, of course it's only readable from one side during either
particular half of the year.
Next easiest to explain the construction of, is the horizontal-dial. Has
shadow all day, all year, and readable from all directions if you're
standing near enough to it. But maybe not everyone is that near to it.
And, after that, the easiest to explain the construction of are the the
flat dials whose dial-plate-normal (perpendicular line) is in the plane of
the meridian: That's a south-facing vertical dial, or a south-facing
reclining dial. (But if the necessary visibility-direction called for it, I
suppose it could be a fairly-nearly-horizontal north-facing reclining dial
too, though it of course wouldn't have as much coverage of hours and
seasons.)
If you want the construction to be easily-explained to people, then you
wouldn't use a declining, or reclining-declining dial. But of course
sometimes visibility-direction requirements could make one necessary,
especially with non-translucent, non-transparent dial-face material.
All this from someone who has never built a durable, waterproof, windproof,
fixed-mounted outdoor sundial :^)
There are a lot of questions that I'd ask about that. I'll save those for
another post, sometime.
Well, one question now:
Were
