INSTITUTE FOR ASTRONOMY
University of Hawaii

Information Bulletin 8

Telescopes

by Dr. Alan T. Tokunaga

1. What are telescopes used for?

The main purpose of a telescope is to collect light. Modern telescopes use a pair of mirrors to collect light and focus it onto an instrument. This instrument, such as a camera with a solid-state detector, then records the information contained in the light.

2. Why are there different types of telescopes at Mauna Kea?

Telescopes are designed and built to gather specific kinds of information at different wavelengths in the electromagnetic spectrum, such as visible, infrared, or millimeter wavelengths. Because the telescopes on Mauna Kea are used to obtain each of these different kinds of information, they have to be different to make the required observations at the highest efficiency possible.

Also, most telescopes on Mauna Kea, like the NASA Infrared Telescope or the Canada-France-Hawaii Telescope, are operated by national or international organizations; others, like the University of Hawaii 2.2-meter telescope and the W. M. Keck Telescope, are managed by institutions. In any case, each operating organization has its own observing goals and has built a telescope to meet those specific observing needs.

University of Hawaii 2.2-meter telescope

3. Is there a best type of telescope?

No; each type of telescope serves a unique purpose and works best at what it is designed to do.

Cross-section of UH 2.2-meter telescope building

4. Do astronomers look through the telescope?

Almost never! Astronomers use detectors that are much more sensitive than the human eye to record incoming light (infrared array detectors or photomultiplier tubes, for example). Because of the special capabilities and sensitivity of these instruments, it is not only unnecessary, but actually inefficient, for astronomers to observe with the naked eye. Also, a TV camera is often attached to the telescope to "see" the sky for the astronomers. Beyond that, computers are used to record and analyze the volumes of information captured by the telescope.

5. What can astronomers learn from analyzing starlight?

A surprising variety of information can be obtained:

* The composition of a star (what elements it is made from)
* The temperature of a star (how hot it is)
* The pressure of a star's atmosphere (how dense its atmosphere is)
* The velocity of a star (how fast it is moving toward or away from us)
* The distance to a star

By analyzing this information, it is possible to understand how a star is born and dies, and how it evolves inbetween. We can also obtain similar information about the planets, comets, and galaxies--all this from analyzing light!

6. What kind of training do astronomers require?

Astronomy is a branch of physics. To pursue a career in astronomy, you must learn physics, mathematics, astronomy, and computer programming.

7. What job opportunities are there in astronomy?

For every astronomer at work at a large telescope, there are normally 10 or more support people helping to keep the telescope operating. These people include electronics and mechanical technicians and engineers, computer programmers, telescope operators, and maintenance and clerical staff.

Prepared by the Institute for Astronomy, University of Hawaii

For more information or additional copies, write to the
Assistant to the Director
UH Institute for Astronomy
2680 Woodlawn Drive
Honolulu, HI 96822

Acknowledgments: Louise H. Good, Wendy F. Nakano, and Karen M. Rehbock.

© 1995 University of Hawaii Institute for Astronomy
Latest revision July 1995

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