lab 3

The following sketches of the moon's appearance were made over about four weeks. Identify the phases and put them in the correct numerical order. One is labeled for you. Picture Order Phase Picture Order Phase A       8       Waning crescent D       3       First quarter B       1         waning gibbous   E       4       Waxing gibbous C       5       Full moon F       2       Third quarter Page 2 – Introduction to Moon Phases From the perspective of an observer above the North Pole, the moon moves clockwise / counterclockwise (circle) in its orbit around the earth. In the diagram below the sun's light is coming in from the right. The moon's location is marked at several points on its orbit. These are the points the moon was at when the sketches above were drawn. Identify each position with the letter of the corresponding sketch. NAAP – Lunar Phase Simulator 3/14

We normally draw the phases of the moon with the terminator (the dividing line between light and shadow) from the north pole to the south pole of the moon. This is how the moon would be seen if it were on the observer’s meridian. We can use the drawing above to determine the amount of illumination and whether it is on the left or right hand side of the moon. Use the drawing above to draw the appearance of the moon in the box below. Open the Moon Bisector Demo and use the simulator to check your answer to the above problem. Part III: Working with the Lunar Phase Simulator The items below will help familiarize yourself with the controls and usability features of the simulator.  If you have not already done so, launch the NAAP Lunar Phase Simulator  The main panel has sunlight, the earth, and moon. The earth and moon can be dragged with the mouse.  Below the main panel, there are animation controls. The moon and earth can be dragged.  The increment buttons move both the moon and earth by the specified time.  The Moon Phase panel shows the current moon phase. Drop down menus will jump to a predefined position. Note that the phases, such as crescent and gibbous, are more broad than the particular point chosen by the presets.  The Horizon Diagram panel displays the point of view of the observer (and you are a second observer looking down on that observer).  The observer’s horizon diagram can be dragged to allow for the most convenient viewing orientation.  The sun and moon on the globe can be dragged around.  In the Diagram Options panel, the show angle option shows the earth-moon-sun angle. The phases are technically defined in terms of this angle.  In the Diagram Options panel, the show lunar landmark option draws a point of reference to more easily observer lunar rotation and revolution. NAAP – Lunar Phase Simulator 6/14

Moon Geometry Age Phase Percent Illumination Sketch 11 days, 9 hours Waxing Gibbous 88% 21 days, 23 hours Third quarter 51.4% 4 days, 1 hour Waxing crescent 17.6% 19 days, 4 hours Waning gibbous 79.2% NAAP – Lunar Phase Simulator 9/14

This module also contains another simulator especially for gaining insight into the lunar phases in the horizon system. Please load the Moon Phases and the Horizon Diagram Simulator . Follow the guidelines below to gain familiarity with the simulator. Please begin by unchecking all options.  Click the option entitled show ecliptic band . Since the ecliptic can be as much as 23.5º away from the celestial equator and the plane of the moon’s orbit is inclined almost 6 degrees to the plane of the ecliptic – the moon can be located in a band almost 60º wide in the sky. We assume for this lab that the moon is always located on the celestial equator. Unclick show ecliptic band.  For simplicity’s sake we identify 8 distinct locations for the sun corresponding to 8 distinct times. Click show sun and use the slider to manipulate the sun’s position. Place the sun at the appropriate location for each of the following times: 6 am, 9 am, noon, 3 pm, 6 pm, 9 pm, midnight, and 3 am.  Place the sun at the noon position (position 3). Note that that the phase of the moon is new in this orientation.Click show moon and place the moon at position 3 as well. Click show phase and show phase on moon disc . Now step through the 8 possible positions by moving the moon eastward. Note that when the moon is one position east of the sun, its phase is waxing crescent. When the moon is two positions east of the sun its phase is first quarter. Move the moon through the remaining phases of the cycle. Thus, there are two general rules for solving problems in the horizon system.  The time is denoted by the position of the sun.  The phase of the moon is denoted by how many (out of the 8 steps) the moon is east of the sun. Question 4: Complete the following table. You are encouraged to visualize the solutions in horizon diagrams drawn on scratch paper or in your head and then use the simulation to check your answer. NAAP – Lunar Phase Simulator 12/14