Lunar Observing Log Part 1: Background This is an evening observation, please plan ahead this observation requires four look-sees of the Moon over the next 7 days. There is no excuse for not doing it, but I will make some exceptions for bad weather. Luckily, the Moon is moving toward full over the next week so it will be easy to spot and up in the early evening. If you want more detailed tips on spotting it, I recommend using SkyGazer (one of the CD-ROMs that came with your book) to locate it for you before you go out. In this figure, the various positions of the Moon on its orbit are shown (the motion of the Moon on its orbit is assumed to be counter-clockwise). The outer set of figures shows the corresponding phase as viewed from Earth, and the common names for the phases. The first thing evident about the lunar landscape is that it's divided by the terminator, the line separating lunar day and night. As the Moon grows
(waxes) during the two weeks after new, the terminator is the line of sunrise, unveiling new terrain as it slowly sweeps across the lunar surface. At full Moon it coincides with the edge of the disk (the limb) and is not seen. In the waning phases, the two weeks after full, the terminator is the line of sunset. A crescent Moon is a visually pleasing combination of dark maria and bright, rugged lunar highlands. This is usually the lunar face that beginning observers first study as every month it's nicely placed in the sunset sky. Try to examine one feature each night you go out. Every formation changes dramatically under different lighting. A crater may appear to be a deep, dark hole at sunrise, turn increasingly saucer-shaped as the Sun climbs the sky for the next few days, and show up as a flat white spot or ring at local noon. As the Sun declines in the lunar west the process is reversed, with shadows now being cast in the opposite direction. Part 2: Phases and Features of the Moon The Moon appears to go through a complete set of phases as viewed from the Earth because of its motion around the Earth, as illustrated in the following figure. Here is an animation of actual lunar phases, and here is a Java applet illustrating the orbit of the moon around the Earth and the corresponding phases of the Moon as viewed from Earth. Notice that you can set this applet to a top view, an Earth view, or both on a split screen, and that you can start and stop the animation with a button. Also, note that in this applet the position of the Sun is shown to the left, whereas in the above figure the view is such that the position of the Sun is to the right.
The lunar surface shows thousands of times more detail than anything else in the night sky, being over 100 times closer than the nearest planet ever gets. Its mean distance is hardly astronomical; 239,000 miles (382,400 kilometers) may be less than you've driven a car during its lifetime. Being so close, the Moon presents a landscape, not a skyscape. So it's fair to say there are really two types of observing: the Moon and everything else.
Ignoring the occasional appearance of exceptionally large sunspots, the Moon is the only heavenly body which shows features to the naked eye-- the Man in the Moon. In the philosophy of Aristotle (384-322 BCE), the Moon's features presented somewhat of a problem. The heavens, starting at the Moon, were the realm of perfection, the sublunary region was the realm of change and corruption, and any resemblance between these regions was strictly ruled out. Aristotle himself suggested that the Moon partook perhaps of some contamination from the realm of corruption. Plutarch suggested that the Moon had deep recesses in which the light of
the Sun did not reach and that the spots are nothing but the shadows of rivers or deep chasms. Today we know that the dark spots are dry lava seas, called "mare" and the white areas are highlands, pocked by billions of years of craters. Part 3: Observations Once you get outside and spot our closest neighbor, please record the following information for each observation: 1. Date and Time 2. Phase (day) and Location of Moon in the Sky. For location, try to line up where the Moon is relative to something on the horizon. Tree? House? Then measure how high it is the sky. Use your hands to measure distance up in the sky. When you come back the next time, measure distance up the same way and then measure distance along the horizon using your hands too. Include this in your daily summary. 3. Details that are visible of the Moon's surface. Craters, maria, etc. See those two pics above and try your level best to identify features by name. I expect you can name some of the features you are seeing, even with the naked eye. Perhaps bring these maps out and make pen marks over top of it about what you are seeing. Something. 4. Every formation changes dramatically under different lighting. A crater may appear to be a deep, dark hole at sunrise, turn
increasingly saucer-shaped as the Sun climbs the sky for the next few days, and show up as a flat white spot or ring at local noon. As the Sun declines in the lunar west the process is reversed, with shadows now being cast in the opposite direction. 5. Questions 5 and 6 are more general and apply to the whole period. Use those details of angles to tell me how much it is moving along from night to night. Questions 1. Day One Observation: What did you see (be sure to include all the details from above for full credit)? 2. Day Two Observation: What did you see (be sure to include all the details from above for full credit)? 3. Day Three Observation: What did you see (be sure to include all the details from above for full credit)? 4. Day Four Observation: What did you see (be sure to include all the details from above for full credit)? 5. What pattern did you notice in terms of time and location of the Moon in the sky? What does that pattern tells us? What would the ancient astronomers have thought? 6. Did you notice it moving across the sky over the course of several days? Which direction (time is important here)? 7. How much later did the Moon rise each night? 8. What did you notice about the Moon's surface? What details were easy to see and which were harder to see? Why was that? 9. Which of the following could never happen? Explain. a. An observer seeing a full moon in the middle of the day (local noon) b. An observer seeing a new moon in the middle of the night (local midnight) c. Both of the above observations are impossible for any observer to see. 10. We define a month to mean the length of time it takes the Moon to go through one complete cycle of phases. If you lived on the Moon, how long would it take the Earth to go through one complete cycle of phases?