Hi Brent,
The line from the sun spot projected on the wall is generally a curved line,
a hyperbola, called a declination or date line. On the equinox, when the
declination of the sun is zero, the line is straight. The curvature
increases day by day with solar declination to a maximum value on the
solstices. Declination lines are standard features on sundials, easily
calculated point by point with geometry and trigonometry.
Regards, Roger Bailey
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From: "Brent" <[email protected]>
Sent: Wednesday, March 30, 2011 8:03 AM
To: "R Wall" <[email protected]>
Cc: "Sundial List" <[email protected]>
Subject: Re: Sundial house
Well I made a test birthday window.
I cut a piece of plywood the size of one window in an east
facing wall. I drilled a hole in the top about 2" diameter.
At sunrise it shines a bright sun circle on my wall that is
about 12 feet away. The sun spot is about 4" diameter.
The edges are crisp and clear.
I was surprised at how bright it is even in the well lit
room.
I was also surprised that it didn't move straight down as
the morning progressed but is moving at an angle. I am
guessing that it is my latitude or co-latitude angle.
Tomorrow I will try and get some accurate marks on it and
measure the angle. I'm curious to see if that angle will change during the
year.
I can see that if I want the spot to shine on a photo at
about eye level, the hole in the window needs to be at the
correct height, which would be in line between the hanging
photo and the east horizon. Obstructions need to be taken into account.
brent
On 3/29/2011 2:58 PM, R Wall wrote:
Hi Bret,
A Birthday window what a good idea. Maybe something smaller
like a wall vent could be turned into a Birthday Window. I
wouldn't want to blacken out a full size window.
Roderick Wall.
-----Original Message----- From: Brent
Sent: Wednesday, March 30, 2011 2:02 AM
To: John Carmichael ; Sundial List
Subject: Re: Sundial house
Hi John;
That's a cool idea for the community center, thanks.
It might be a challenge the closer we get to the equator as
it might be hard to view.
I was thinking about roof pitch also. If my southern
facing roof was pitched 90 degrees to my co-latitude it
would be parallel to the earths' axis. So when I look up
a groove of the corrugated tin roof it would point directly
at the north star or southern cross. That has the same
challenge the closer you get to the equator.
How about a birthday window:
On the east facing wall have a blacked out window with a
hole in the middle. This might cast a spot of light on a
different place on the wall each sunrise. When it is your
birthday, hang your photo where the sun spot is shining and
every year thereafter the sun will shine on you on your
special day. I suppose you could do that for all family
members. That sounds fun. The kids could watch their
birthdays coming by following the sun spot.
brent
On 3/29/2011 7:27 AM, John Carmichael wrote:
How about this:
On one of the buildings, design a southern facing roof.
Angle the roof so
that it is equal to the latitude. Then place a gnomon on
the roof and make
the entire southern roof into a giant polar sundial.
Everyone in the
village would be able to see and use it.
John C.
-----Original Message-----
From: [email protected]
[mailto:[email protected]] On
Behalf Of Brent
Sent: Tuesday, March 29, 2011 7:20 AM
To: Sundial List
Subject: Sundial house
Hello again;
I have the opportunity to design some ultra low cost
housing for slum resettlement. Just because they are low
cost doesn't mean they can't be cool places to live.
here are a few ideas I have:
1. I could orient the houses to true north. The east or west
walls could have a long horizontal window that could act as
a sunrise/sunset calendar. The window could have a center
mullion that would cast a shadow on the wall around the
room which could be marked as a calendar.
2. Orient the gables north and south and leave the gable
ends exposed with no overhanging eaves and set vertical
dials on the north or south or both. Maybe I could make a
stencil or two and simply paint on dial faces. Or show the
new owners how to do that and let them mark their own.
I would appreciate any other ideas.
They just need to be inexpensive and simple to use.
Here is a cool saying that seems appropriate:
Sol Lucet Omnibus
The Sun Shines for Everyone
brent
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