Exam 4: Telescopes: the Tools of Astronomy

Stars do not twinkle; the instability of the atmosphere causes this effect.

The Hubble Space Telescope gives us its best resolution with X- rays.

Like radio and optical astronomy, infrared astronomy is easily done with ground- based telescopes.

Adding a secondary concave lens of carefully chosen different glass to the primary lens on a refractor allows

Name two advantages of larger telescopes over smaller ones.

In the future, adaptive optics will greatly enhance the resolution of the Hubble Space Telescope.

Explain the basic principle behind the VLA.

The focus reflector needs only a single optical surface to form images.

What is the resolution of a telescope?

All modern large optical telescopes are refractors.

Which type of telescope has the simplest light path?

Why is a CCD image much faster to obtain than a photograph?

Contrast the main mirrors of Newtonian and Cassegrain designs.

CCD detectors gather light 10- 20 times faster than the most sensitive photographic film.

The Cassegrain reflector needs a primary concave main mirror and a smaller, convex secondary mirror to reflect light back through a hole in the primary.

Mt. Palomar's 200" Hale telescope is the largest reflector now in service.

The Earth's atmosphere is the major factor limiting the use of ground- based radio telescopes.

What is a CCD, and how does it work? Why is it replacing film?

There are ground- based telescopes much larger than Hubble, yet the HST still reveals the faintest objects yet seen. Explain.

The light- gathering ability of a telescope is most dependent on the diameter of its primary objective.