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How to Draw a Waning Moon for Science

People have been making detailed observations of the Moon since the Babylonians 3,000 years ago, and the detailed observation and recording of its phases played an important part in the growing understanding of the Earth's place in the solar system. It is quite remarkable that the relative sizes and distances of the Earth, Moon and Sun allow them to perfectly eclipse each other. However, this is not what causes the waning of the Moon. Rather, it is our position relative to the Moon that determines how much of the Moon's illuminated side, and how much of its dark side we can see at any one time.

Things You'll Need

Compass
Pencil
Ruler
Thin card
Craft knife
Lamp
Eraser

Instructions

- 1
  Set the distance between compass tip and pencil at something easily divisible by 15. The exact size you choose will depend on whether you are drawing for your book, a poster or other format. For the exercise book, a good size to work with is 15/16". The following instructions will refer to a Moon drawn to this size, but can be easily scaled up to draw a larger Moon.
- 2
  Draw 15 circles arranged in a row. These will form the phases of the moon as seen on each day of the waning from Full Moon to New Moon. Faintly draw a horizontal line across the center of each circle, passing from one side, through the center point to the other side. Starting at one side, mark along this line every 1/8" of an inch. This should produce 14 marks between one side of the circle and the other.
- 3
  Draw another circle of the same size onto a thin card. Cut it out and cut it in half.
- 4
  Leave the first one of the row of circles blank, as this is the Full Moon. Lay the half circle of card on the second Moon in the row so that it fills up the right hand side of the circle. Draw a faint line along the page against the flat edge of the card to to help you keep it in place. Position the lamp directly above the circle facing down. Switch on the lamp.
- 5
  Hold the half circle of card between finger and thumb and, keeping the flat edge pressed against the line you drew on the page, lift the curved edge slightly away from the card. Keep lifting the curved edge and watching at the shadow of the card on the page. When the edge of the shadow runs through the first of the marks you drew, trace the line of the shadow onto the page with a pencil.
- 6
  Move the card to the third Moon in the row and repeat the procedure but continue lifting the curved edge until the shadow's edge passes through the second mark you drew. Again, trace the line and then move on to the next Moon, each time tracing the line of the shadow's edge as it passes through the next mark in the sequence. On the seventh circle, the card will switch from leaning over to the right to standing vertically to leaning over to the left hand side of the circle.
- 7
  Shade in the section of each circle to the right of the curved line you have drawn on each. Erase the measuring marks and the vertical line that you drew. Label each type of Moon, starting with Full Moon on the first in the sequence and finishing with New Moon on the last, which should be completely shaded.

Astronomy