Models of the Sky - Celestial Sphere We need to simplify some locations in the sky now. We can talk about stuff that is directly over head, or we can say stuff is at your zenith- this just means the location right over your head. You have a personal zenith and what is there depends upon where you are on the Earth, what time of day or night it is and what time of the year it is. There is also a term for the exact opposite of zenith, but we don't really care about that since it would be in the direction of the ground and there are no stars visible down there. Another special direction is the horizon , though that is not really one particular direction, but sort of, well, your horizon. To be kind of technical, the ground meets the sky at the horizon, and generally, there are 90º between the horizon and the zenith (especially in Iowa). If you do want to get specific about the horizon, you could say the southern horizon, the northern horizon, etc. Here's a rather surprising concept that you might not have known about - the ancient astronomers
This is the end of the preview.
access the rest of the document.