Basic star charting is first learning the most common constellations.
CONSTELLATION 101
To learn the constellations you need to learn not only their shapes but also their relative sizes. Let’s start with shapes. Find Cassiopeia on the Winter Chart and notice its shape…. roughly a “W.” (You can remember this if you think of the “W” as the chair or throne on which Cassiopeia, the Queen, sits).
You have seen that Orion, Taurus, and Cassiopeia each have a different shapes (H, V, and W). You can also see that they differ in size. For example, Orion is much larger than Cassiopeia. But how much of the real sky does Orion cover? For example, could you cover it with your thumb at arms length?
CONSTELLATION SIZES
When we talk about the size of a constellation, we are referring to how big it looks to us. That is, how much of the sky does it span. Technically, we measure size on the sky by angular measure.
Astronomers traditionally use angles to measure sizes and distances on the sky. To understand how, imagine two sticks joined at one end with a nut and bolt so they can be spread apart. If you hold these sticks up to your eye and sight along one to a given star and along the other to another star and then measure with a protractor the angle between the sticks, you will have found the angular distance between the two stars.
The above technical definition works well, but for ordinary sky watching, it is helpful to start with a simpler scheme using just your hand at arms length. If you hold your arm out straight and spread your fingers, the angle from tip of thumb to tip of little finger is about 20 degrees for most people.
Thus, your spread hand will span slightly more of the sky than the width of the Big Dipper’s bowl. Similarly, if you make a fist, then the angle between the knuckles at arm’s length is about 5 degrees. These are of course only approximate, but will help you estimate relative size and distance in the sky.