Sunlight
The first activity that you can do is to show a child how the sky changes from day to night. Simply have the child stay up until it is time for sunset. Take them to a place where they can see the sunset properly. Explain how as the sun sets, the rays of sunlight pass through more and more of the atmosphere. This causes only the red light to be apparent. Eventually no light can be seen from the sun and outer space becomes visible.
The Moon
The next phenomenon to teach children about is the moon. Take the child outside every night for a month and show them how the moon changes phases. Focus on the New Moon, Full Moon, Waning and Waxing phases. Show them how the earth blocks the rays from the sun to make each phase.
Stars
The last and most prolific part of astronomy is the categorization and study of stars. There are a staggering amount of stars in the universe and we can see only a fraction of them from earth. The easiest way to teach children about stars is to teach them constellations. Constellations are groupings of stars as they appear in specific shapes. They make star groups recognizable in the sky. The first one that you can teach the child is Orion. It is an iconic shape of stars that look like a man. The three stars in his belt point left to the brightest star in the sky, Sirius B. Another important constellation is the Big Dipper, a grouping of stars that looks like a ladle which is part of the Ursa Major Constellation.