# MW5202 Sun and Moon Homework

## Goals of the Homework

• Take three pictures showing the change in the setting (or rising) position of the Sun in the course of the semester
• Take three pictures showing the changes in the shadow cast by a ring
• Take pictures of the Western horizon on the first three days of the lunar month to determine the day of the first visibility of the lunar crescent, i.e., the first day of the Muslim month
• Take a picture of the first daytime visibility of the Moon
• Estimate the tilt of the Moon when it is a crescent close to the horizon
• Estimate where and when the Sun can be seen from your window in the course of the year
 Sunset in August Sunset in September

## Detailed Description

On a day in January take a picture showing the rising or setting position of the Sun. You don't need to take it just when the Sun is rising or setting, just make sure that you get both the Sun and the horizon (or whatever you see instead of the horizon at your place) in the picture, and that the picture gives a sense of where the Sun is rising or setting. Use a compass (the magnetic declination is negligible in Singapore) to estimate how many degrees the rising/setting point is from due East/West. If your compass doesn't have a degree scale, you can use a protractor or use your hand as described in the links at the bottom of the page.

On a day in January suspend a ring-shaped object vertically in the East-West plane. What does the shadow of the ring look like on the ground? Take a picture of the ring that illustrates this. You do not have to do this on the same day as you take the picture of the Sun. You can take this picture any time of the day. You can take this picture anywhere. It is important that the ring is in the East-West plane. Include a compass in your picture and indicate north. Hint: It is easier to get good pictures if the ring is fairly large, but narrow.

Repeat the sunrise/sunset picture in February and near the March equinox around March 21. Repeat the ring experiment in February and on the zenith passage around March 24. You may not be able to take pictures on the day of the equinox, but I want them close to the equinox. Compare the observations and explain the differences.

You can chose sunrise or sunset depending on what is most convenient for you, but please use the same for all three observations. It is important that the sunrise/sunset pictures are taken from the same place, so that the pictures are easy to compare.

 Small crescent in the top middle: Evening of second day of the Chinese month, start of first day of the Muslim month
• I want photos of the Moon on each of the first three days of the Chinese lunar month that starts after February 22. (I don't want to ruin Chinese New Year for you!) However, if the new Moon occurs after sunset on the first day, I want pictures of day two through four. If we have an evening lecture, we will either skip the picture if we are not likely to see the Moon, or take a "field trip" to take pictures.

In 2011, there is a new Moon on March 5 at 04:45:46. We cannot expect to see the Moon at the evening on March 5, but MUIS claims so, so please try to take a picture on that night. If you don't see the Moon, just take a picture of the dark westsern sky between sunest and moonset. Try to get a picture on March 6. If you cannot get it on March 6, then also try on March 7.

• I want a picture of the Moon on the first day it is visible during daytime (before sunset). I do not know which day this will be. You may have to try several days.
• For each observation include the following.
1. Photo of the Moon. For the three crescents I want a photo showing the horizon and the Moon. (Or a building or something else that indicates where the horizon is.)
2. Time of the photo.
3. Age of the Moon by indicating the day of the month in either the Chinese, Islamic calendar or an Indian lunisolar calendar. (But please don't use an Indian solar calendar!)
4. Approximate azimuth using a compass.
5. Approximate altitude using your hand as described in the links at the bottom of the page.
6. For the three crescent Moons close to the horizon, use a protractor to measure the approximate tilt of the Moon. By the tilt I mean the angle between the line between the two "horns" and the horizon. Discuss briefly whether the angle of the tilt matches the theory.
7. Time of sunrise, sunset, moonrise and moonset for that day.

Take a picture showing the view from the room of one of your group members. I want a picture that shows the horizon, or at least buildings on the ground. I also want an aerial photograph (using for instance Google Earth). Draw on the picture where you estimate the path of the Sun to be at the solstices and the equinoxes. Try to estimate what time during those days you can see the Sun from your window. Depending on the view from your window, not all the three paths may be visible, but I want a picture that gives a reasonable impression of when the Sun will be visible from your room on those three dates. I'm not expecting exact values, just reasonable estimates that shows that you have learned the key concepts about the motion of the Sun.

You will be graded on the clarity of your presentation. The pictures must clearly illustrate the concepts and confirm that you made the observations.

Please submit both soft copy and hard copy.

## More Details of the Homework

• You may not be able to see the Moon because of the weather. In that case, I want pictures of the Western horizon at times when you could have seen the Moon, i.e., between sunset and moonset. However, if you claim that you couldn't see the Moon on a certain day, and several of your classmates get nice pictures, you have a problem.
• The most crucial observation is the one for the day that starts the Muslim month, usually the second or the third day of the Chinese month. Use Khalid Shaukat's Moonsighting.com, MoonCalc or Accurate Times to predict when the crescent will first be visible. Make a serious effort to see it that night. Don't give up before the time of moonset. If you can't see it, I want at least a picture of the western part of the sky between sunset and moonset.
• This is a major exercise in team management! You can do it while on trips, dates or whatever! On the crucial first day of the Muslim month, you may want to divide your group into several teams in case one part of the island is cloudy or one one team has picked a bad spot. For the other observations, you may schedule different people in your group to attempt to make observations on different days.
• It is very hard to take good pictures of the Moon. Please don't despair; it's just as hard for everybody else! Please don't try to impress me with photos from the web or past homework!