domingo, 22 de septiembre de 2013

Sun polar chart III

How to build your own Sun polar chart:

It has been some time since my last blog, but I did not want to leave in abeyance how to draw a Sun chart. Before the summer we could see what it was and how it is used a Sun polar chart:

Where is exposed how a Sun chart allows us to determine when sunlight falls through a window or a skylight. However, we need a Sun chart for our latitude and is therefore important to know how to draw it. So I wrote the following post:

Where was solved how to start drawing a stereographic Sun chart ... the problem is that the drawing is a bit tedious, so I decided to solve it step by step in two posts. This is the second and last post on sun charts.

After a fifth step, determined in the previous post, we draw the solar chart with the months of the year:

The sixth step corresponds to the drawing of the hours on the trajectories of the months of the year. Let's start with the six o'clock in the morning. As we have indicated the hours on the trajectories of the equinox, we just have to choose the point corresponding to the six, which indicates the change from night to day. From that point we draw a plane perpendicular to the ecliptic, which cuts at two points on the sphere. These two points are projected in stereographic form (to the lower vertex of the sphere) and are indicated on the axis noon. Then we draw a circle passing through the two points and the center is located on the axis:

Likewise, we draw the rest of paths hours. The drawing shows the trajectory of the seven o'clock:

With hourly and monthly paths we have our solar chart:

Although we need an important drawing: the parallels:

Once we have drawn parallels, are projected in stereographic form (to the lower vertex of the sphere) as shown in the picture:

That's it! We have our Sun polar chart and it may be used to calculate when light falls through a window, a courtyard or a skylight. Of course, for a given latitude:

And that's all for now. There is still much to discover (skylights, atriums, design methods, and a long etcetera) and I'll try to show it in the next few weeks.

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