The Solar

System: A6: Telescopes

The Telescope• Telescope – device that makes distant object

appear closer

– A Dutch lens maker, Hans Lippershey, invented the telescope in 1608

–Galileo made it famous in 1610 when he used it to see objects in the night sky–Galileo was the first person

to ever see sun spots, Saturn’s rings, and the large moons of Jupiter

Electromagnetic Radiation• To understand how a telescope works, it is

useful to understand the nature of electromagnetic radiation

– Forms of Radiation – energy that travels through space in waves

– Visible Light – Light that can be seen is one type of electromagnetic radiation

–Other types of radiation include: radio waves, x-rays, gamma rays, and more

Electromagnetic Radiation– Electromagnetic Spectrum – includes the entire

range of visible and non-visible waves

– Recall, a wave length is the distance from the crest of one wave to the crest of the next

– Also recall that wave lengths increase towards the red end of the spectrum

Draw in your notes

In which direction does the energy increase?

Types of Telescopes• Optical Telescopes – use lenses or mirrors to

collect and focus light making objects appear larger and brighter–Refracting Telescope – uses convex lenses– Convex Lens – clear glass curved so that

the middle is thicker than the edges– A simple refracting

telescope, like the one Galileo used, has two convex lenses at the ends of a long tube

Types of Telescopes– Light enters through the larger objective lens– The objective lens focuses the light a certain

distance from the lens– That distance is the focal length of the lens

– The smaller lens is the eyepiece

– The eyepiece lens magnifies the image produced by the objective lens

Types of Telescopes–Reflecting Telescope – uses a curved mirror

to collect and focus light– Invented in 1668 by Isaac Newton– Instead of an objective lens, the mirror

focuses the light

– They can be made much bigger

– Less optical irregularities and brighter images

– All the largest telescopes today are reflecting

Other Types of Telescopes• Other Types of Telescopes – collect and

focus different types of electromagnetic radiation (instead of visible light)–Radio Telescope – Curved, reflecting

surfaces used to detect radio waves.– Surface reflects and concentrates radio

waves like a mirror in a refracting scope

– The concentrated waves are projected onto a small antenna

– The larger the curved surface is, the more waves it can collect

Other Telescopes– Infrared Telescope – Use infrared

light to detect celestial bodies

– Can be ground-based, air-based, or in space

– They contain a camera and a special solid-state infrared detector which must be cooled to cryogenic temperatures

– Because water vapors in the air absorb infrared, ground-based scopes are usually on mountains in very dry climates

– Putting them in space eliminates the atmosphere’s interference

Other Types of Telescopes–Other Telescope – Other types of telescopes

include ultraviolet, x-ray, and gamma ray scopes

– To understand how the images of the telescopes differ, below are pictures of the Crab Nebula taken with each.

Video

In Closing• Why do you think telescopes were first

invented?

• Why are telescopes important to the study of astronomy?