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Name: Harut
Status: student
Grade: 9-12
Location: CA
Country: USA
Date: Winter 2011-2912

I have wondered for a while now if astronomers that use telescopes for studies or other things actually look through them. Do astronomers really look through the telescopes with their own eyes or does a special instrument/camera like thing take a picture of the object(s) the telescope is pointing towards, and then project it onto a/many computer screen(s)? If you know why they do/do not look through the telescopes, I would really like to know.

Dear Harut,

Great decision, although you may change it again as you get older. These days astronomers use electronic detectors rather than their eyes. However, most of my personal observing involves directly looking through a telescope with my eyes.

So that is the way it seems to be these days. Good question!

Sincerely David H. Levy

Very seldom do astronomers using large telescopes actually look with their eyes. There are several reasons: 1. Compared to electronic detectors, the eyes are insensitive, and are limited to wavelengths of "light" -- electromagnetic radiation -- from about 400 to 700 nanometers. This is a small slice in the wavelengths from the ultraviolet to the far infrared. In addition, with a "flip" of a switch the wavelengths being observed can move from one wavelength to another. Also the electronic detectors can have "what they see" electronically recorded for later inspection, that is, there is a permanent record of the observations. Often astronomers want to look at special very narrow emissions from stars. They do this by passing the incoming "light" through an instrument called a spectrophotometer, also called a spectroscope. This instrument separates the incoming light into different places according to the wavelength of the light. Every element and/or compound has a characteristic set of wavelengths. This provides information that the eye cannot provide. Also light coming from "outer space" is shifted slightly which gives information about how fast and, with some more analysis, how far the object is. This is called the Doppler effect, or the Doppler shift. You can Google this to get more details.

In short, electronic detectors give much more information than the eye possibly can. The beautiful photographs you see of stars, nebulae, etc. are constructed by reassembling the electronic "pictures" back into photographs in the photo lab.

A word of advice if you intend to pursue astrophysics as a career. Take as much math as you possibly can, then take some more. It will serve you well no matter where your career plans take you.

Vince Calder

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