 So, if we go back and we think about the sky dome, and I'm going to do this little diagram of this is the sky dome that we've talked about in the textbook and in the class, and this is going to be the ground, right? So we have the sky dome, and you can kind of see that, you know, the, this dome that we have could be, is this, is a hemisphere, first of all, and we could project that dome onto multiple different surfaces. So the first projection that we will do is, is going to be orthographic, okay? And essentially an orthographic projection is going to be what happens if I were to try to take a flat piece of paper, maybe like a cylinder of paper, and I were to try to wrap that cylinder around, right around this sky dome, right? So I'm going to have, everybody see the cylinder that's wrapping around? So I'm going to want to project points onto that flat surface, and ultimately that flat surface is going to be printed out, and we're going to have our basis for our sun charts in terms of the azimuth angle, right? So the rotation along here along the, the planar rotation along the horizontal is the azimuth angle, and the angle from the ground up, the vertical rotation is going to be the altitude angle, right? Of course the complement of that, if we were talking about the sun, would be the zenith angle, which is why we could represent this as 0 to 90 and 90 down to 0 with the zenith angle. We have two conventions for plotting the azimuth angle, the one, excuse me, the one is to make east negative, so we can go negative 180 degrees and west positive 180 degrees, where this 0 is pointed at the equator, right? Of course the alternate is to begin in the north with 0 degrees and to work your way clockwise to all the way around to 360 degrees, in which case south, not the equator, is going to be positive 180 degrees. Now this is the convention that a lot of the solar world has used for some time, however this is the standard convention that has been established through meteorology, so we tend to use both flexibly, but just know that in general the 360 degrees is an accepted standard, all right? So if we then go to the next page and we think about that same sky dome, and got our ground, and instead of trying to project it off to the side, we are effectively lying on the ground and we are going to project upwards, and this way the azimuth angles are rotating around in a circle just like the azimuth angles would be doing here on the ground. The altitude angles, however, are going to be represented as arcs where the higher in the sky you are, the closer to the center of the circle, and how do we see that? Well we look at it like this, and we are going to start to see the center point, I am going to put south here, we know that south is in the northern hemisphere where the sun is at its highest point, so we are going to see arcs in the sky that look like this, going from, in our case, east to west, this is going to be summer time, this is going to be winter time, when the sun is low in the sky versus high in the sky. So here is going to be an alpha of 90 degrees, and the ring around the bottom is going to be an alpha of 0 degrees. It's a little different plot, the lines are going to be flipped from what you are used to in orthographic projection, but you can do both of these at the Oregon site for sun plots.