Part 2: The Galileoscope



In this section of the lab, you will be using the Galileoscope, which is a plastic replica of the telescope Galileo would have used to spot the moons of Jupiter, lunar features, and more. Listed below are the pieces you need to complete this exercise.

а а а 1. The telescope tube that consists of the focusing tube, locking ring, dew shield, and objective lens.

а а а2. The modern eyepiece (larger lens)

а а а3. The Galilean eyepiece (smaller lens)

а а а4. The ring cap

а а а5. The Barlow tube


1. What are some of the differences between refracting and reflecting telescopes? (Drawing a diagram may be helpful.)

2. Is the Galileoscope a refracting or reflecting telescope? What type of celestial objects would you be likely to see using the Galileoscope? What kinds of objects would not be ideal for viewing with it?

3. What is an example of a reflecting telescope?

Take the telescope apart by removing the dew shield, twisting the locking ring, and lifting the halves of the body apart, as shown in the image at the top of the page. You should examine the objective lens. Be careful to only pick it up by the edges as to not smudge the lens. When you put it back together, the thin part of the lens should be facing out, i.e., toward the object you are viewing.

4. Why does the objective lens of the Galileoscope consist of two separate lenses fused together? You may need to research this answer.

Using the Eyepieces

Reassemble the Galileoscope. Be sure to put the end of the focusing tube interior to the first notch in the telescope tube. Otherwise, you will not be able to focus the telescope correctly.

You will now compare the view using three different eyepieces. The first is the Galilean eyepiece. You will need the small eyepiece and the ring cap as shown in the image below. The smaller side of the lens is inserted into the telescope.

5. Describe the view using the Galilean eyepiece. You should think about the magnification and the field of view. How do you think this would have affected Galileo’s observations?

You will now use the modern lens, which is the larger of the two eyepieces. It does not require any attachments.

6. Describe the view using the modern lens and compare the magnification and field of view to the Galilean eyepiece. Do you notice anything else that is different with the modern lens?

Now, you will assemble the Barlow lens. The Barlow lens requires the modern eyepiece, the Barlow tube, and the Galilaen eyepiece without the ring cap. The small eyepiece goes into the small end of the Barlow tube, the modern eyepiece goes into the larger side, and then the whole lens goes into the telescope with the small eyepiece in first.

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