Telescope Exhibit Page 2 of 2

Telescope Exhibit Page 2 of 2

Telescope Exhibit

Brief Summary

This exhibit was added in late 2007. The label copy can be seen below. This exhibit benefits from facilitation.

How do telescopes work?

trapping light

The basic idea is simple: The more light a telescope collects, the better. Astronomers sometimes call telescopes “light buckets” or “light traps.”

aperture/magnification/exposure

Find out how aperture size, magnification, and exposure time work together to affect what you can see with a telescope.

backward and upside down

Through most telescopes, things look backward and upside-down. Correcting for this normal effect of lenses on light can distort the image, so astronomers prefer to live with it. Besides, there’s no up or down in space!

APERTURE SIZE [TELESCOPE AT FAR LEFT]

Bigger apertures collect more light, which makes things look brighter.

·  The aperture is the opening at the far end of a telescope. Telescopes are made for collecting the light that comes from faraway objects. The bigger the “bucket,” the more light it can collect—and the brighter the image.

Ø  Turn the wheel to see the difference between a smaller and bigger aperture.

Ø  Does making the aperture smaller cut off part of what you can see?

MAGNIFICATION [MIDDLE TELESCOPE]

Magnification makes things look bigger.

·  Magnification works great for viewing some objects, like the Moon, the planets, galaxies, and nebulae. It does nothing for “single-point-of-light” objects such as stars.

Ø  Adjust the lens to see how using more or less magnifying power affects what you see.

Ø  Does changing the magnification change the brightness?

EXPOSURE TIME [TELESCOPE AT FAR RIGHT]

Longer exposure times give more detail by collecting light over time.

·  To increase exposure time, you need to have your telescope hooked up to a camera. The longer the exposure, the more detailed the picture.

Ø  Use the buttons to capture images with different exposure times. Wait a few seconds for your image to come up on the screen.

Ø  How do features look different with a longer exposure time? Are they brighter and clearer?

[With five buttons, labeled as below]

1/16 second 1/4 second one second

exposure

shorter longer

time

What’s the difference? [CUTAWAY REFRACTING/REFLECTING TELESCOPES]

Refracting telescopes use curved lenses to focus light into the eyepiece.

·  Refracting telescopes are usually long, to provide enough distance for the light to focus down—called focal length. The very first telescopes, like the one Galileo used, were long, narrow refracting telescopes.

Reflecting telescopes use mirrors to do the same thing in a different way.

·  Reflecting telescopes can be much shorter, because the light bounces back and forth as it focuses. Today’s astronomers mostly use reflecting telescopes, because it is very expensive and difficult to make—and support—huge, heavy, precisely curved lenses for large-aperture telescopes.

Operating Tips

·  The “Thermal Imaging” section on the OCC mounted on the column controls this area. Choose “presentation lighting” to light up the area, and/or chose a microphone that projects into this area. These two features are useful in both the facilitated or show modes.

·  Visitors often put their eye up to the telescope with the CCD camera (exposure section). Use this as a teaching moment! Try telling the visitors that yes, that is where you would look , and on this telescope we have a camera there “looking” through the telescope.” (then proceed with explanation)

·  As of printing, the object seen in the telescopes is a Hubble Image, not something that can in fact be seen with a typical off-the-shelf telescope. These telescopes can, however, see such objects as the Moon (including great detail), the rings of Saturn (at certain times), the moons of Jupiter, some nebulae and star clusters, and the Andromeda Galaxy.