# Count column 3 5 calculate the number of degrees

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count (column 3). 5. Calculate the number of degrees moved from image to image (column 4). Note: The Moon moves in a roughly circular orbit around the Earth. A circle contains 360°. The Moon completes its orbit around the Earth in about 27.3 days. Thus, each day, the Moon moves about 13.2° around the 360° orbit. Multiply (13.2) × (number of days from col. 3) to get degrees moved from prior image. 6. Calculate the number of degrees of longitude for each image (column 5) starting at 270o. Add the degrees moved for the next image (from column 4) to the longitude determined for the prior image. When you reach 360o, start over at 0o. Round to 1 decimal place.
7. Plot the Moon’s orbital position on the polar coordinate graph paper given as Figure 2. You will have to plot longitude vs. scale distance, D. On the graph paper, longitude starts at the bottom, labeled 0°, and increases counterclockwise. This will correspond to the true direction of the Moon’s orbital motion as viewed from above the Earth’s north pole. To plot the first data point, place the edge of your millimeter ruler along the line labeled 270° (longitude). Be sure that 0 mm is at the origin of the graph paper, which corresponds to the Earth’s position on this diagram. Now measure out along the 270° line and place a pencil dot at your value of D for a longitude of 270°. Continue in this manner for the remaining data in Table 1 (columns 5 and 7). You may have to plot some points in the margin outside of the grid lines. This is OK. When all the data points are plotted, connect the points by drawing a smooth line through them (this is your orbital path). Draw freehand (do not use the compass). 8. If you examine the plotted data on Figure 2, you can see that they are NOT centered on the Earth. In order to draw the Moon’s orbit, you must first establish the orbit’s center. Open your compass equal to the D ave calculated in step 3. Remember to use the edge of your millimeter ruler to properly set the compass. Locate the center by placing the compass point on four or five (or more) of the plotted data points and draw a small arc near the center of the graph. Ideally, these should all cross at one place, the center. In reality, they will show you only approximately where the center should be. Put a dot where you estimate the orbit’s center is. Label the center of the Moon’s orbit “CMO” where you placed your dot. (Note that these steps count for points in the grading.)