Notes for Each Chapter

Choosing Activities

We encourage you to develop your own personalized "track" of activities. Although the chapters are designed to be independent, you will find it useful to have completed some activities before others. We also suggest that you work on two activities at once. You can then progress on an observational activity on clear nights and on a laboratory activity on cloudy nights.

Keeping a Notebook

Answering Questions

Recording Data

Drawing Graphs

Do not connect the dots. Draw a straight line or a smooth curve through the dots if one seems to fit the data.

Writing a Summary

• What exactly have you done? Your answer should address what you have done rather than what you have learned. Thus, you should write, "I have measured the height of the Tower with a quadrant," rather than, "I learned how to use my quadrant."
• What observations did you make to accomplish your goal? What equipment did you use?
• What were your results? How accurate were your results? How precise? If there is a "right" answer, is it within your errors?
• What were the major sources of error in the experiment?
• What could be done to improve your results with the equipment available to you? What further experiment(s) could you do to learn more?

Turning in the Activity

These notes are intended to supplement the text, not to replace it. If we do not mention a section, we think that section is self-explanatory. Do not skip anything unless we specifically state that you can omit it.

Chapter 1: Principles of Measurement (Required)

The required activity consists of chapters 1 and 2.

Section I

Assemble the cross-staff and omit the rest of this section (stop at the diagram).

Section III

Omit Question 1. You'll answer a similar question later.

Section IV

Make five measurements (not 10) at 1, 4, and 16 meter (or yard) distances. Convert each measurement to an angle with your nomograph, then calculate the range, average, standard deviation (using Snedecor's Rough Check, page 5 second column), and percent error of the angles obtained at each distance.

Make a new plot like the one you made in Section III showing the average, the average plus the standard deviation, and the average minus the standard deviation at each distance. (Don't plot the smallest and largest values, as the book asks.)

Section V

Skip Question 2. Question 3 refers to the numbers in the paragraph above it.

Section VI

Question 4 is different from Question 1, read carefully. For Question 5 "proportionally" means twice the distance gives exactly half the angle. Use the errors you calculated for your angles in Section IV to answer the question. On page 8 the text instructs you to repeat your measurement from four meters with the medium sight on your cross-staff. Skip this exercise, and don't answer Question 10.

Section VII

Measure each altitude five times (not 10).

Section VIII

Section VIII is optional.

Section IX

To calibrate your hand and fist, move forward and backward in the hall with your arm extended. Stop when your hand (or fist) just covers the 75-cm length on the wall. Your hand (or fist) now covers the same angle from your eye as the 75-cm marks. Standing at the same spot, use your cross-staff to measure the angle. The angle you measure is the calibrated size of your hand or fist. To measure your finger, mark a gap 5 cm wide and move to the distance from the wall where your finger just covers the gap. Measure your distance to the wall and use the equation on p. 7. Make each measurement once and calculate errors using the values given in the text as the "actual" sizes.

Take your observations the first clear night you can! Once we've had a couple of clear nights, we can't accept weather as an excuse for not turning this chapter in on time.

Section I

Skip Parts B, D, and E. Do each measurement 3 times.

Section II

Skip Parts C and D.

Section III

This section can be completed before Sections I and II (except Question 2 which still must be answered). Questions 4 and 5: Note today's date.

The dates of this semester's lunar phases are given at the end of this handout. Your two observations will need to be at least a week apart, so be sure to plan for this. The first quarter moon rises before sunset, while the last quarter moon doesn't come up until well after midnight.

Speak with an instructor about check-out procedures if you will need binoculars outside of class time.

Section I

Drawings with the telescope must be good enough to unambiguously identify several features.

Section II

The Sun shines from the right in all photographs; virtually all the round features are craters.

Observations will be taken over the course of one lunar cycle (28+ days). You can obtain an SC1 chart from one of the instructors.

Section I, Part A

Take data every 3-4 days, not every 2.

Section II

Omit the scale drawing described in the last paragraph of this section. You should be able to answer Question 6 without doing the drawing.

There are two ways to do this chapter, but the more interesting of these offers you the chance to track a planet's motion through the sky. If you would like to do this, you should start as early in the semester as possible.

Omit either Section II or Section V.

Section II

Obtain an SC1 chart from one of the instructors. Observations will take between a few days and a few weeks; you will need clear skies. Mars is the easiest planet to observe.

Section IV, Part C

In Figures 9b and 9d, the larger star symbols represent the star of smaller mass. The star with larger mass has a smaller orbit (just as the Sun has a smaller orbit than the earth).

Observations for this activity can be conducted during the day at home.

Section I

Be sure to use a pointed gnomon, and mark the point of the shadow on the paper.

The azimuth is the angle between due north and the Sun. Since you have recorded a shadow opposite (180$^\circ$ from) the Sun, you need to measure the angle between the shadow and due south to obtain an azimuth.

Please turn in the sheet with your actual observations.

Section II

Omit this section.

Section III

Austin is at approximately 98 degrees W longitude.

Do Chapter 7 after completing Chapter 6. Again, observations can be done at home. You will need two observations two weeks apart.

Section II, Part A

Graph your measurements of altitude vs. time to determine the maximum altitude and time at local noon. Part B: Omit.

This is an in-lab activity that will take 1 or 2 periods. Use 4-6 lenses and one mirror.

Sections I and II

If you cannot get a sharp focus when close to the light, move the lens and screen farther away from the light. A sharp focus is necessary.

Section III

Focal length is a property of every lens. Once you have determined the focal length for a lens, you can use that focal length in any situation you place the lens in.

Section V

The image distances you found from across the room in Section III are approximately equal to the focal lengths for each lens. You can use them for the focal length in this section.

Section VI

Section VI is optional.

You may check out a camera, cable release, and tripod; ask an instructor about check-out procedures. We provide film and a darkroom.

Section I, Part G

Questions 8 and 9 each have two answers.

Section II, Part A

Watch the rewind crank when you first wind your film. If it does not start to turn after a few winds, the film was misloaded and must be corrected.

Section II, Part B

The text is unclear on page 73. Take a series of exposures of a distant streetlight, bracketing your exposures. Choose a street light that is distant enough to appear as almost a point source; the streetlight is a model of an unknown star.

For the star trail photographs a tripod is beneficial but not necessary. You can lay the camera on the ground (for overhead shots) and lean it on a rock, pointing it approximately. The camera's field of view is wide, so you will capture some stars. Be sure to use a cable release.

Section IV

Rewind the film before you open the camera!

Solar observations can probably be completed over the course of a week; anything else can be done in one clear night.

Section VI

You certainly don't need to observe all the different kinds of objects to observe here. Meet with an instructor to work out a reasonable list.

This is an in-lab activity.

Section II

Omit Section II.

Section IV

AST 103L and AST 302 use spectrometers that are scaled differently. If you are using a 302 grating found in the lab, the parts of the spectrometer should be separated by 10.75" instead of 20". Make the slit as small as possible for all your observations. Record observations to the nearest 20 Å.

Section VII

Observe the sodium lamp in the lab instead of a street lamp or the Sun.

Sections VIII and IX

Omit both these sections.

This activity requires only one short observation; all other data are in the text.

Section I

All references to Figures 1 and 2 are reversed. The speed of light given in Question 2 is incorrect. The correct value is c = 300,000 km/s = 3 x 10⁸ m/s.

Section II

From each corner of the roof draw a picture of the object whose distance you are measuring in relation to the background object. Your pictures should look like Figure 4 on page 98.

Section III

Omit Section III.

Section IV

Read Appendix 3 before beginning this section. The instructors have copies of the H-R diagram on page 107 for you to put in your notebook.

This is an in-lab activity; we have prints of the Palomar plates you need.

Section III

Measure the sizes of at least six stars, making sure that the stars you measure have a temperature given. We will provide an overlay of Figures I and II.

This is another in-lab activity using the Palomar plates. Ask one of the instructors for the overlay (page 129).

Fall 1997 Lunar Phases

Other Astronomical Dates

Bright Planets

Location of Austin, Texas

Austin is at approximately 30 degrees N latitude and 98 degrees W longitude.

Painter Hall Telescope

Painter Hall houses public nights when you can observe at a 9" refracting telescope with one of the Student Observatory Directors. Public nights occur on clear Saturday nights from 8:00 to 10:00. Student nights are on clear Fridays from 9:00 to 10:00.

The telescope is easy to use, and any UT student can be checked out to observe with it. Talk to the Directors, Divas Sanwal (RLM 17.312 471-7418) or Feng Ma (RLM 13.112, 471-6486) about procedures. Lara Eakins in RLM 13.122 (471-1307) also has a handbook that explains how to go about qualifying to observe.