Explorations: An Introduction to Astronomy (Arny), 7th Edition

Chapter 5: Telescopes

Thought Questions

1
Apart from magnification, how do binoculars help you see better? All else being equal, what difference will you see with 50-millimeter lenses versus 25-millimeter lenses?
2
Put a pencil straight down into a glass of water. Notice whether the pencil looks bent. Now tilt the pencil and note how its apparent bending changes. How does this illustrate why light from objects near the horizon is refracted more strongly?
3
Why isn't there a hole in the image from a reflecting telescope because the secondary mirror blocks some light? Is your answer true even if there is a hole in the center of the primary mirror, like in the Cassegrain focus shown in figure 5.7?
4
Is it better to have a telescope with a high resolving power or a high magnification? Explain why.
5
The Very Large Array is a radio interferometer observatory in New Mexico with twenty-seven 25-meter telescopes. In its widest arrangement, it has the resolving power of a telescope 36 kilometers in diameter. What is better about this arrangement than a single 36-kilometer diameter telescope? What is lacking compared to a single 36-kilometer dish?
6
Why does the useful resolving power of a ground-based telescope with a 2-meter diameter mirror not match its theoretical value?
7
It is difficult to observe 1-nanometer, 1-millimeter, and 100-meter radiation with ground-based telescopes. What are the reasons, for each?
8
If you look with binoculars down a beach on a hot day, you will see that distant objects appear shimmery. How is this related to astronomical "seeing"?
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