ASTR 110L Spring 2008 Section 1 Observing Lunar Features
Sketching the Moon
Sketch tonight’s Moon, and include the following: a. (1 pt.) The terminator b. (3 pts.) The outlines of major maria that are visible tonight c. (1 pt.) Major rayed craters that are visible tonight (most important: Tycho & Copernicus, plus any others) d. (1 pt.) Other prominent craters (include central peaks, if any), mountain ranges, or other features e. (1 pt.) Date, time, telescope/eyepiece/filter, and location
Tips • Use unlined paper. It is easiest to start with a circular outline (like the one provided to you in class). • Use pencil. Sketch with lines (either light or heavy, for sharp boundaries of features) and shading (for shades of gray or shadow). Decide whether you want shading to represent light or dark — I recommend pencil for dark, and blank white paper for light. (Make a note on the side of the sketch if you choose the opposite of this.) • First, draw the terminator on your sketch. This provides a very useful reference for further sketching. Craters and mountains stand out best along the terminator, which is the line between day and night on the lunar surface, while craters in broad daylight tend to wash out and are harder to see. (Thought question: why?) • Features on the dark side (night side) of the Moon will be visible only if the phase is a very slim crescent; usually, no features are visible, and you don’t need to worry about sketching anything there. Just shade it in. • Second, draw the outlines of the major maria. If they are dark, shade them a bit. They should look noticeably different (both in real life and on your sketch) from the surrounding highlands. • Third, sketch the major rayed craters, making sure to show the direction and extent of their rays. (Even though the rays are usually light, you can use your dark pencil. Make an explanatory note if you wish.) • Finally, you can draw a few of the other largest (unrayed) craters, perhaps those with prominent central peaks; any obvious mountain ranges; or other features. It’s impossible to draw every crater. Start with the general outlines of the largest features and most salient/obvious features (like rayed craters), then work your way down to smaller ones if time permits. • Always label your sketch with date, time, telescope/eyepiece/filter used, and location. f. (1 pt.) Later, label the direction of North on your sketch g. (2 pts.) Later, use a Moon atlas/map to label the following features (not all are necessarily visible, depending on the phase of the Moon): Mare Crisium Mare Imbrium Tycho Crater (rayed) Mare Fecunditatis Mare Nubium Copernicus Crater (rayed) Mare Tranquillitatis Mare Humorum Optional: Mare Nectaris Oceanus Procellarum Any other major craters or Mare Serenitatis mountain ranges on your sketch that you can identify using maps
questions on back…
Homework Questions
At home, answer the following questions (on a separate sheet of paper):
1. How do the lunar maria and highlands look different to the naked eye, or with a telescope? Specifically: a. (2 pts.) Which has the higher or lower albedo? Why? b. (2 pts.) Which is more or less heavily cratered? Why?
2. (3 pts.) Look at Mare Crisium (“Sea of Crisis”) with the telescope. What do you think happened to create Mare Crisium, and what about its appearance supports this? Is the floor of the mare heavily cratered or mostly smooth? Do you suspect that the little craters on the floor of Mare Crisium occurred fairly recently, or very early in the life of the Moon?
3. (3 pts.) Look at Mare Serenitatis (“Sea of Serenity”) with the telescope. Can you see the ray crossing the mare? (It’s visible on the Moon map, too.) Which major rayed crater on the Moon does it look like that ray originated from? Physically speaking, what are crater rays? Which craters should we expect to see rays around: very recent or very old craters, and why?
4. (2 pts.) The lunar surface is covered by a few-inches to a few-meters-thick covering of regolith. What is it, and how do you think it forms? (Remember that the Moon has no air, atmosphere, or wind.)
5. (2 pts.) Why doesn’t the Earth have many impact craters on its surface… or does it? (There are several reasons — give as many as you can think of.) Relatedly, why doesn’t Earth have a layer of regolith… or does it?
Bonus (? pts.): Discuss anything else interesting. Sketch it on your Moon diagram, and try to identify it later.
MOON
Date & time:
Telescope/Filter used:
Use the above circle to represent the edge of the Moon, NOT the edge of your telescope’s field-of-view.