What is a star chart & how it works?
A star chart is a snapshot in time. It's a shorthand drawing, a two-dimensional representation of a four-dimensional subject. It has to take into account the location of the person on Earth, the location around the Ecliptic of each of the planets and the signs of the Zodiac, the “arc” or height above or below the horizon of each of the planets, and the time all of this occurred. It can be a very complex drawing.
The Chart has several different elements. First, the spoked circles, looking like a bicycle wheel, represent the Zodiac and the Houses.
The Zodiac are the constellations in the sky at the time the person was born. The Star Chart is an attempt to locate the position of the Zodiac in the sky. This is the backdrop against which the rest of the chart is mapped.
The Houses are a separate, concentric circle, like a wheel within a wheel. The Houses are based on the Zodiac, but separate. Think of the circle of houses as a second backdrop.
Next, each of the planets, the Sun, and the Moon, are all charted and their positions marked. This, finally, is our foreground.
The first “planet” to be charted isn’t a planet at all, it’s the Sun. The reason it comes first is because the location of the Sun determines the Sun Sign, or the overall sign of the Zodiac for this person.
Each planet (including Sun and Moon) will fall within a House. That planet is then said to rule that house. Each of the twelve Houses controls a different aspect of a person’s life. If a planet falls within a house, it’s a sure bet that that planet is going to have a major influence over that aspect—above and beyond whatever the general tendencies of the person born under that sign might be.