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Resolution Project

Introduction

 

            Resolution is the ability to distinguish objects.  From the introductory handout, you know that resolution is dependent on two parameters as illustrated by the equation:

 

                                    q= 1.22 (l/d)

                                    q = resolution in radians

                                    d = diameter of telescope

 

This activity is designed to help you understand resolution and how a change in either of the two parameters in the above equation affects resolution.  This activity will also help you to gain an appreciation for the different methods of observations that astronomers use and the difficulties they face in studying astronomical objects

 

Activity One – The match game

 

            You will be given a set of pictures with various objects on them.  The pictures represent objects observed using different telescopes.  There are five different objects, but some have more than two matching pictures.  Your goal is to place pictures from the same object together.

 

Discuss your results.  What wavelength of light was used for each photo

 

List some features of the objects you can infer from the photographs

 

Looking at the correct matches, why do you think astronomers use these different methods for observing the same object?

 

Activity Two – How does diameter and wavelength affect the resolution of an object?

A. There will two sets of objects placed against a wall (place sets one at a time).  You will observe these pictures from a distance of 10 m, first with your eye, then with a telescope. Each set will be a different color and consist of five shapes. 

           

Procedures and Observations:

 

                        1. Put together telescope provided following the directions provided

a. what is the diameter of the lens (not eyepiece) of the telescope? (measure before putting it together)

2.  Record what you see with your eyes

a. set 1                         b. set 2                         c. set 3

3. Record what you see with the telescope

a. set 1                         b. set 2                         c. set 3

 

4.  Examine the shapes close up.  Did the shapes recorded differ from your close up observation?

 

5. Were some colored shapes easier to observe than others?  If yes, how would you explain this?

 

6. Calculate the resolution of the eye (aperture ~ 3mm) and telescope at each color.

 

7. Move closer to the objects until you can resolve them with your eye, and measure this distance.

            a. Do the distances vary with color?  Are the distances significant?

 

b. using the resolution of the eye for each color, calculate the distance where you should be able to make out the objects.  You will need to measure the diameter of the shapes used.

 

c. Is there any difference between the calculated and observed distances?  Explain.

 

d. Figure out the angular size of the object.  Does it correspond to your calculation of the eye’s resolution?

 

e. Figure out the maximum distance your telescope could resolve the objects

 

f. Can astronomers take advantage of the method you used in procedure 7?  Why?

 

D.  Conversion to radio telescope

1. Using the resolution obtained by the your telescope (use red light wavelength), estimate the size of radio telescope you would need to get the same resolution at the 21cm wavelength

 

Activity 3 – How does wavelength affect resolution?

A. We will be using the 37 m radio telescope at the MIT Haystack Observatory to observe the Crab nebula (or Cyg A?) at different wavelengths (1.3cm and 6 cm).

1. What do you find as you shift from a longer to shorter wavelength

2. Calculate the resolution of the 37 m telescope at these wavelengths

B. Compare the images you received from the 37 m to the VLA picture (provided) of the same object

C. How does a change in wavelength affect the resolution?  Why?

D. Compare the difference the colors made to resolution to the different radio wavelengths.  Is there a significant difference?  Why or why not?

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