Telescopes From the Ground Up

Teacher Page: Lesson Plan

Teacher Pages:
Science Background
Lesson Plan
National Standards
Grab Bag
Computer Needs
Back to the Lesson


Desired Learning Outcomes
New Vocabulary
General Misconceptions
Preparation Time
Execution Time by Module
Physical Layout of Room
Procedure / Directions
Evaluation / Assessment
One Computer Classroom
Classrooms without Computers
Home Schooler


This activity is modular and can be used by both middle school and high school audiences. In the “Get to the Root of It” section, students use illustrated text and interactive graphics to explore the relationship between the operation of telescopes and light, color and optics. Students can use this section for review, learning the basic prerequisites, or remediation.

Through reading and interactive graphics, students explore the history of telescopes from Galileo to the Great Observatories as it relates to scientific and technological advances. Students will increase their knowledge of technological advances in telescope design, investigate the history of astronomy and telescopes, identify how technological advances allowed science to advance, and discover how scientific knowledge has aided technological advances.

Desired learning outcomes:

"Get to the Root of It" section:

· Compare reflection to refraction.
· Explain how light is dispersed by a lens and how this affects image quality.
· Explain how the shape of a lens or mirror can affect the image quality.
· Describe how a refracting telescope forms an image.
· Describe how a reflecting telescope forms an image.

Explore the history of telescopes from Galileo to the Great Observatories:

· Identify the major events associated with the development of telescopes from Galileo to the Great Observatories.
· Describe and justify a sequence of events.
· Describe how technological advances have improved telescopes.
· Describe how science has advanced the technology associated with telescopes.
· Describe how improvements in telescopes have allowed scientists to make new discoveries.


Before attempting to complete this lesson, the student should:

· Be able to read at an eighth-grade level.
· Be able to interpret information.
· Have basic note-taking skills.
· Be able to read to answer comprehension questions.
· Know that the electromagnetic spectrum is a continuum of wavelengths (also, frequency and energy), artificially broken into seven sections called radio waves, microwaves, infrared light, visible light, ultraviolet light, X-rays, and gamma rays.
· Know that light travels in straight lines unless something alters its path.
· Know that mirrors reflect light, whereas lenses refract light.
· Know that telescopes gather and focus more light than the human eye can.

Note: All prerequisite information content can be found in the “Start with the basics” section of "Get to the Root of It."

New vocabulary:


A mixture of two or more metals. Brass (a mixture of copper and zinc) and bronze (a mixture of copper and tin) are common alloys.


A type of telescope mounting that supports the weight of the telescope and allows it to move in two directions to locate a specific target. One axis of support is vertical (called the altitude) and allows the telescope to move up and down. The other axis is horizontal (called the azimuth) and allows the telescope to swing in a circle parallel to the ground. This makes it easy to position the telescope: swing it around in a circle and then lift it to the target. However, tracking an object as the Earth turns is more complicated. The telescope needs to be adjusted in both directions while tracking, which requires a computer to control the telescope.


To make larger or more powerful; increase. Radio signals are amplified because they are very weak.


An electrical device used to send or receive electromagnetic waves. The aerial (a long piece of metal attached to the front or rear fender) on a car is the antenna for the radio.


An orderly arrangement or impressive display. For radio telescopes, an array is a group of individual radio dishes that work together. The VLA (Very Large Array) has 27 telescope dishes arranged in a "Y" pattern.


A scientist who studies the universe and the celestial bodies residing in it, including their composition, history, location, and motion. A scientist who studies celestial objects using visible light is called an optical astronomer while one who studies celestial objects in the radio wavelengths is called a radio astronomer.


Astronomy is the study of the universe and the celestial bodies that reside in it, including their composition, history, location, and motion.

Atmospheric distortion

The blurring of an image due to the layer of gases surrounding the surface of Earth. As starlight travels through the atmosphere, pockets of air act like little lenses and bend the light in unpredictable ways. This distortion causes stars to appear to twinkle.

Big Bang

A broadly accepted theory for the origin and evolution of our universe. The theory states that the observable universe started roughly 15 billion years ago from an extremely dense and extraordinarily hot "bang."

Black hole

A region of space containing a huge amount of mass compacted into an extremely small volume. A black hole's gravitational influence is so strong that nothing, not even light, can escape its grasp. Swirling disks of material — called accretion disks — may surround black holes, and jets of matter may also be associated with the black hole.

Cassegrain telescope

A type of reflecting telescope whose eyepiece is located behind the primary mirror. The primary mirror is cast with a hole in the center. When light enters the telescope, it reflects from the primary mirror to the secondary mirror. The secondary mirror reflects the light back through the hole in the primary mirror to the eyepiece.

Charge-coupled device (CCD)

An electronic detector that records visible light from stars and galaxies to make photographs. These detectors are very sensitive to the extremely faint light of distant galaxies. They can see objects that are 1,000 million times fainter than the eye can see. CCDs are electronic circuits composed of light-sensitive picture elements (pixels), tiny cells that, placed together, resemble mesh on a screen door. The same CCD technology is used in digital cameras.

Diagram demonstrating chromatic aberration caused by a standard convex lens.

Chromatic aberration

Visible light is made of different colors. When visible light passes through a glass lens or a prism, it gets dispersed, or split, into its many colors. A lens focuses each color at a different point, causing a fringe of color to appear around bright objects.

Looking at only red and blue light:


A moveable mirror system used in solar telescopes. The mirror follows the Sun and keeps its image in the same location as Earth rotates.

Colliding galaxies

A galactic "car wreck" in which two galaxies pass close enough to gravitationally disrupt each other's shape. The collision rips streamers of stars from the galaxies, fuels an explosion of star birth, and can ultimately result in both galaxies merging into one. Note: Stars do not collide when galaxies merge, due to the great distances between stars.

Diagram comparing and contrasting concave versus convex concepts with respect to mirrors and lenses.

Concave vs. convex


The outermost layer of the atmosphere of a star, including the Sun. The corona is visible during a solar eclipse or when special adapters or filters are attached to a telescope to block the light from the star's central region. The gaseous corona extends millions of kilometers from the star's surface and has a temperature in the millions of degrees.

Cosmic background radiation

Electromagnetic energy filling the universe that is believed to be the radiation remaining from the Big Bang. It is sometimes called the "primal glow." This radiation is strongest in the microwave part of the spectrum but has also been detected at radio and infrared wavelengths. The intensity of the cosmic microwave background from every part of the sky is almost exactly the same.

Crown glass

Originally the main material used to make flat planes of glass for windows, it is composed of soda-lime glass. It can be used to make lenses and prisms. Crown glass bends and disperses, or spreads out, light less than flint glass.

Dark matter

Matter that is too dim to be detected by telescopes. Astronomers infer its existence by measuring its gravitational influence. Dark matter makes up most of the total mass of the universe.


A device used to measure the amount of electromagnetic radiation emitted by celestial objects. Frequently, detectors are used to sense light that is not visible.


The distance from one side of a circle to the other measured through the center. For telescopes, the diameter of a lens or mirror is measured from one side to the opposite side, passing through the center.

Diagram demonstrating how a prism uses refraction to create a spectrum.


Visible light is actually made up of different colors. Each color bends by a different amount when refracted by glass. That's why visible light is split, or dispersed, into different colors when it passes through a lens or prism. Shorter wavelengths, like purple and blue light, bend the most. Longer wavelengths, like red and orange light, bend the least.

Double stars

A system of two stars that are gravitationally bound to each other. They orbit each other around a common center. They can also be called binary stars.

Electromagnetic spectrum

The entire range of wavelengths of light. Arranged from longest to shortest wavelength, it includes radio waves, microwaves, infrared, visible, ultraviolet, X-rays, and gamma rays. All electromagnetic waves travel at the same speed in space.


A special kind of elongated circle. The orbits of the solar system planets are elliptical.


The process of allowing electromagnetic radiation to fall on light-sensitive materials such as photographic films or plates. An exposure is also the image created by the process. A long exposure time is needed in order to obtain an image of dim and distant celestial objects.


The lens or lens group closest to the eye in an optical instrument such as a telescope or microscope.

Images comparing different fields of view.

Field of view

The field of view is the area of the sky visible through a telescope.

Flint glass

The lead glass that was produced in the United States and the United Kingdom prior to the 1860s. This glass is used to make telescope lenses and prisms. Flint glass bends and disperses, or spreads out, light more than crown glass.

Diagram demonstrating the definition of focal length with both a convex lens and a concave mirror.

Focal length

Focal length (shown in red) is the distance between the center of a convex lens or a concave mirror and the focal point of the lens or mirror — the point where parallel rays of light meet, or converge.

Diagram of how a perfect lens creates a focal point.

Focal point

The focal point of a lens or mirror is the point in space where parallel light rays meet after passing through the lens or bouncing off the mirror. A "perfect" lens or mirror would send all light rays through one focal point, which would result in the clearest image.


Describes the number of wave crests passing by a fixed point in a given time period (usually one second). Frequency is measured in Hertz (Hz).


A collection of stars, gas, and dust bound together by gravity. The smallest galaxies may contain only a few hundred thousand stars, while the largest galaxies have thousands of billions of stars. The Milky Way galaxy contains our solar system.

Gamma Rays

Light with the shortest wavelengths and the highest energies and frequencies in the electromagnetic spectrum; also called gamma radiation. Gamma rays are produced by violent events such as supernova explosions. They are also produced by the decay of radioactive materials. Gamma rays can kill living cells, so it is good that Earth's atmosphere can stop them. Gamma radiation is used in medicine to kill cancer cells.


A spinning wheel mounted on a non-stationary frame that stabilizes and points a space-based observatory. This spinning wheel resists applied external forces and tends to retain its original orientation in space. For example, balancing on a moving bicycle is easier than balancing on a stationary one because of this tendency.

Infrared (IR) light

A region of the electromagnetic spectrum that has slightly longer wavelengths and lower frequencies than visible light, but is not visible to the human eye. This region of light is comparable to the range of sounds that are too low for the human ear to hear. Infrared light can be detected as the heat from a fire or a light bulb.


Any device that measures and/or records energy from astronomical objects. Some astronomical instruments include spectrometers, photometers, spectroheliographs, and charge-coupled devices.


The process used to combine the signal from two or more telescopes to produce a sharper image than each telescope could achieve separately.


An instrument that combines the signal from two or more telescopes to produce a sharper image than the telescopes could achieve separately.


A carefully ground or molded piece of glass, plastic, or other transparent material that causes light to bend and either come together or spread apart to form an image.

Lens doublet

A set of two lenses, one concave and one convex, made from different types of glass. Together the lenses correct both spherical and chromatic aberrations. A single lens alone cannot correct these aberrations.

Magnetic field

A region of space in which magnetic forces may be detected or may affect the motion of an electrically charged particle. As with gravity, magnetism has a long-range effect and magnetic fields are associated with many astronomical objects.


Enlargement in the size of an optical image. For telescopes, magnification is not as important as the ability to gather light, which depends on the diameter of the primary lens or mirror.


The process of enlarging the size of an optical image.


Electromagnetic waves found in the region between infrared and radio wavelengths. Microwave wavelengths fall between one millimeter and one meter. Microwaves can be used to quickly heat and cook food.

Milky Way

The Milky Way, a spiral galaxy, is the home of Earth. The Milky Way contains more than 100 billion stars and has a diameter of 100,000 light-years.


The support structure for a telescope that bears the weight of the telescope and allows it to be pointed at a target. The mountings of today's research telescopes also allow astronomers to track the object as it appears to move across the sky.


A very small fraction of a meter. There are a billion (1,000,000,000) nanometers (nm) in one meter.


A cloud of gas in space, usually one that is glowing. Historically, "nebula" was a general term used to indicate any light or dark patch of the night sky that was "fuzzy," or not sharply defined, as a star or planet would be.

Neutron star

An extremely compact ball of neutrons created from the central core of a star that collapsed under gravity during a supernova explosion. Neutron stars are extremely dense: they are only 10 kilometers or so in size, but have the mass of an average star (usually about 1.5 times more massive than our Sun). A neutron star that regularly emits pulses of radiation is known as a pulsar.

Newtonian reflector

A type of reflecting telescope whose eyepiece is located along the side of the telescope. When light enters the telescope, it reflects from the primary mirror to the secondary mirror. The secondary mirror reflects the light at a right angle through the side of the telescope to the eyepiece.


The act of noticing or perceiving something. In science, observations refer to noting or recording a fact or occurrence. A telescope is a tool astronomers use to make observations of celestial objects.


A building, group of buildings, or spacecraft specifically designed and fitted with equipment to study celestial objects.


A person who grinds lenses and mirrors.


The science that deals with the properties of light; in this case specifically dealing with the way light changes directions when it is either refracted and dispersed by a lens or reflected from a mirror.


The path followed by a body moving in a gravitational field. For example, the planets travel around the Sun because the Sun's gravitational field keeps them in their paths.

Diagram comparing a spherical surface versus a parabolic surface.

Parabola vs. sphere

If cross-sections of a spherical surface and a parabolic surface were made by slicing each surface in half, these would be the shapes you would see:

Perfect lens

The "perfect" lens does not exist. Due to the nature of glass, light is dispersed when passing through glass. In the case of convex lenses, red light bends less than blue light, so the focal points are in different places, making the image blurry. A single lens cannot counter this effect.


Regularly occurring changes in the appearance of the Moon or a planet. Phases of the Moon include new, full, crescent, first quarter, gibbous, and third quarter.


A technique for measuring the brightness of celestial objects. Astronomers measure the brightness of celestial objects with photometers.

Primary lens

A large convex lens in a refracting telescope that captures light from celestial objects and focuses it toward the eyepiece.

Primary mirror

A large concave mirror in a reflecting telescope that captures light from celestial objects and focuses it toward a smaller secondary mirror.


A prism is usually a triangular-shaped piece of glass used to refract, or bend, light. The shape of the glass causes the light to disperse, or spread out, as it bends, producing a rainbow of colors from the white light.


An eruption of gas from the chromosphere of a star. Solar prominences are visible as part of the corona during a total solar eclipse. These eruptions occur above the Sun's surface (photosphere), where gases are suspended in a loop, apparently by magnetic forces that arch upward into the solar corona and then return to the surface.


A neutron star that emits rapid and periodic pulses of radiation. A neutron star is an extremely compact ball of neutrons created from the central core of a star that collapsed under gravity during a supernova explosion. Neutron stars are extremely dense: they are only 10 kilometers or so in size, but have the mass of an average star (usually about 1.5 times more massive than our Sun). A neutron star that regularly emits pulses of radiation is known as a pulsar.


A quasar is the bright center of a galaxy, believed to be powered by a supermassive black hole. The word "quasar" is derived from quasi-stellar radio source, because this type of object was first identified as a kind of radio source. Quasars also are called quasi-stellar objects (QSOs). Thousands of quasars have been observed, all at extreme distances from our galaxy.


Radiation is a term used to refer to any and all wavelengths of the electromagnetic spectrum. Arranged from longest to shortest wavelength, electromagnetic radiation includes radio, microwaves, infrared, visible, ultraviolet, X-rays, and gamma rays.

Radio sources

Celestial objects that give off radio waves. These sources can be stars, pulsars, galaxies or even a cloud of gas between the stars.

Radio waves

The region of the electromagnetic spectrum with the longest wavelengths and lowest frequencies. Radio waves are about 100,000 times longer than visible light waves.


The part of the radio telescope that detects long wavelength electromagnetic radiation and converts it to an electrical signal so that we can sense it.

Diagram demonstrating reflection of light off a surface.


Reflection occurs when light changes direction as a result of "bouncing off" a surface like a mirror.

Reflector (Reflecting telescope)

A type of telescope, also known as a reflecting telescope, that uses one or more polished, curved mirrors to gather light and reflect it to a focal point.

Diagram demonstrating the effect of refraction of light.


Refraction is the bending of light as it passes from one substance to another. Here, the light ray passes from air to glass and back to air. The bending is caused by the differences in density between the two substances.

Refractor (Refracting telescope)

A type of telescope, also known as a refracting telescope, that uses a transparent convex lens to gather the light and bend it to a focal point.

Resolution (Resolving power)

A measure of the smallest separation at which a telescope can observe two neighboring objects as two separate objects.


The ability of a telescope to distinguish objects that are very close to each other as two separate objects.


A flash of light produced when gamma rays strike a certain material. The high energy of gamma rays makes them hard to capture but they can be detected using scintillation.

Secondary mirror

A small mirror in a reflecting telescope that redirects light from the larger primary mirror toward the light-sensitive scientific instruments. In a Cassegrain-type telescope like the Hubble Space Telescope, the secondary mirror is slightly convex and directs light from the primary mirror back through a hole in the center of the primary mirror.

Solar flares

A sudden and violent outburst of solar energy that is often observed close to a sunspot or solar prominence; also known as a flare.

Solar panels

Two rigid, wing-like structures that convert sunlight directly into electricity to operate a space telescope's scientific instruments, computers, and radio transmitters. Some of the energy generated is stored in onboard batteries so the telescope can operate while in Earth's shadow.

Solar telescope

A special reflecting telescope designed to study our closest star, the Sun. Solar telescopes differ from normal telescopes in that they are stationary and use small tracking mirrors to direct sunlight into the primary mirror. This is necessary because the Sun appears to move across the sky due to Earth's rotation.

Spectrograph (Spectrometer/ spectroscope)

An instrument that spreads electromagnetic radiation into its component frequencies and wavelengths for detailed study. The instrument is similar to a prism, which spreads white light into a continuous rainbow.


An instrument used in solar telescopes to photograph the Sun in a single wavelength of light. Different wavelengths reveal different features of the Sun's surface.


The study and analysis of the light from a celestial object. A spectroscope, spectrograph, or spectrometer is used to spread white light into a rainbow of colors.


The entire range of electromagnetic rays from the longest radio waves to the shortest gamma rays. Arranged from longest to shortest wavelengths, the spectrum of electromagnetic radiation includes radio waves, microwaves, infrared light, visible light, ultraviolet light, X-rays and gamma rays.

Diagram demonstrating a couple of spherical lenses and mirrors.

“Spherical” lens or mirror

A lens or mirror is called “spherical” if its shape comes from a sphere. Here are some examples of spherical mirrors and lenses:

Spherical aberration

Spherical aberration is an optical defect of a lens or mirror caused by its rounded shape. Spherical lenses and mirrors produce a distorted (blurry) image.

Diagram demonstrating spherical aberration caused by a spherical lens.

Spherical aberration in lenses

The shape of a spherical lens causes a problem called spherical aberration.

In spherical aberration, parallel light rays that pass through the central region of the lens focus farther away than light rays that pass through the edges of the lens. The result is many focal points, which produce a blurry image. To get a clear image, all rays need to focus at the same point.

Diagram demonstrating spherical aberration caused by a spherical concave mirror.

Spherical aberration in mirrors

The shape of a spherical telescope mirror causes a problem called spherical aberration.

In spherical aberration, parallel light rays that bounce off the central region of a spherical mirror focus farther away than light rays that bounce off the edges. The result is many focal points, which produce a blurry image. To get a clear image, all rays need to focus at the same point.


A huge ball of gas held together by gravity. The central core of a star is extremely hot and produces energy. Some of this energy is released as visible light, which makes the star glow. Stars come in different sizes, colors, and temperatures. Our Sun, the center of our solar system, is a yellow star of average temperature and size.


Random noise in a radio receiver. It can also be heard in telephone lines and cell phones.


A sunspot is a region on the Sun's photosphere that is cooler and darker than the surrounding material. Sunspots often appear in pairs or groups with specific magnetic polarities that indicate electromagnetic origins.


The explosive death of a massive star whose energy output causes its expanding gases to glow brightly for weeks or months. A supernova remnant is the glowing, expanding gaseous remains of a supernova explosion.


An instrument used to observe distant objects by collecting and focusing their electromagnetic radiation. Telescopes are usually designed to collect light in a specific wavelength range. Examples include optical telescopes that observe visible light and radio telescopes that detect radio waves.

Ultraviolet (UV) light

A region of the electromagnetic spectrum that has slightly shorter wavelengths and higher frequencies than visible light, but is not visible to the human eye. This region of light is comparable to the range of sounds that are too high for the human ear to hear. Too much ultraviolet light causes sunburns.

Visible light

The narrow region of the electromagnetic spectrum that is visible to the human eye. This band includes wavelengths between about 400 and 700 nanometers. (1,000,000,000 nanometers equal 1 meter.)

Diagram showing the definition of a wavelength.

Wavelength and frequency

Light is measured by its wavelength (in nanometers) or frequency (in Hertz).

One wavelength
equals the distance between two successive wave crests or troughs.

Frequency (Hertz)
equals the number of waves that passes a given point per second.


X-rays have a higher frequency and energy level than UV light but not as high as gamma rays. These energetic waves can penetrate the skin but are absorbed by bones, so doctors use X-rays to look through the skin at bones and teeth.


Identifies the magnifying power of a lens or mirror. For example, a 50-power telescope makes the image 50 times larger than it is when viewed without the telescope.

X-ray sources

Celestial objects that give off X-rays. These exotic objects are producing very energetic radiation and include black holes, neutron stars (pulsars), supernovae remnants, and the centers of galaxies.

X-ray telescope

A special telescope used to detect X-rays — high-energy electromagnetic radiation. The high energy of X-rays means they will go through, rather than bounce off, a "normal" telescope mirror. To prevent that, the mirrors of an X-ray telescope are arranged so the rays skip across them, much like a stone skips across the surface of a lake.

General misconceptions:

About Light:

Misconception: Visible light is the only type of light.
Fact: Visible light is just a tiny slice of radiation that makes up the electromagnetic spectrum. In order from lowest energy to highest energy, and longest wavelength to shortest wavelength, the radiation types are: radio, microwave, infrared, visible light, ultraviolet, X-rays, and gamma rays.

Misconception: All radiation is harmful.
Fact: All radiation is not harmful. Light is a form of radiation. All parts of the electromagnetic spectrum are considered radiation, but only X-rays and gamma rays are made up of harmful, ionizing radiation. Ionizing radiation is dangerous because it can penetrate body tissues and cause cell damage. Ultraviolet light from the Sun causes sunburn, which is a common form of “harmful” radiation. Radiation with wavelengths equal to or longer than visible light (radio, infrared, and visible light) is considered harmless.

Misconception: All parts of the electromagnetic spectrum can be viewed from Earth.
Fact: Most of the light in the electromagnetic spectrum is absorbed or deflected by our atmosphere. Only visible light and radio waves penetrate the atmosphere, with small portions of infrared and ultraviolet light also reaching the ground.

Misconception: The Earth’s atmosphere, air pollution, and light pollution do not interfere with telescopes on the ground.
Fact:All of these factors reduce visibility. Telescopes are launched into space to avoid these problems.

About Telescopes

Misconception: Telescopes have always been powerful tools that astronomers use to look at objects very far away.
Fact: Telescopes began as simple “spyglasses” and have evolved into powerful tools.

Misconception: All telescopes have the same design.
Fact: There are two classes of telescopes: refractors and reflectors. The design of all refractors is very similar, but the design of reflectors can vary depending on how and where the final image forms.

Misconception: Telescopes continue to be built with larger, single mirrors to view the heavens.
Fact: Multiple mirrors must be used to construct very large telescopes.

Misconception: Telescopes are judged by their ability to magnify objects.
Fact: In general, magnification, which is determined by the focal length of the primary mirror, is not as important as the ability to gather light (dependent on the diameter of the mirror) and the ability to separate two closely spaced objects (called resolution).

Misconception: Astronomers make observations by looking through the eyepiece lens of a telescope.
Fact: Today’s research telescopes rely on charge-coupled devices (CCDs) to record the light collected by the telescope.

Misconception: Telescopes are built on mountains To get closer to the astronomical objects being observed.
Fact: Building telescopes on mountains places the telescopes above most of Earth’s atmosphere in an area where there is less light and air pollution (since few people live on mountains). If the telescope is on a very high mountain, then it is above most of the water vapor in the atmosphere, so infrared astronomy can be done. (The water vapor in the atmosphere absorbs infrared light.)

About Space Telescopes

Misconception: Space telescopes are manned satellites, with astronauts living and conducting research on them as they orbit Earth.
Fact: The telescopes are unmanned and controlled from the Earth. Astronomers request observation time on the telescopes and conduct their research on Earth.

Misconception: The Hubble Space Telescope can only "see" the visible area of the spectrum.
Fact: The Hubble telescope can collect visible light from (magnify) objects so that astronomers can see them more clearly. The telescope also can detect light that is invisible to the human eye, such as infrared and ultraviolet.

Misconception: Space telescopes take pictures of celestial objects, like taking snapshots with the family camera.
Fact: Space telescopes do not use film to take images. The telescopes instead take digital images, which are transmitted to Earth. Scientists do not think of space telescopes as giant digital cameras in space, but rather as scientific instruments that observe objects for analysis. These observations can be converted into pictures, but pictures are not the telescopes’ primary purpose.

Misconception: Space telescopes can observe celestial bodies better than other observatories because they are closer to them or because they travel to the celestial bodies.
Fact: Space telescopes are close to Earth, and most orbit Earth. (The Spitzer Space Telescope is in an Earth-trailing orbit.) They produce clearer images than ground-based telescopes because they are above Earth's atmosphere. The Earth's atmosphere distorts our view of objects in space.

Preparation time:

· Time necessary to download computer software to support the lesson.
· Teachers should allow time to preview the lesson and to read the science background pages. These pages will provide additional content that will help teachers to answer questions posed by students.
· By previewing the lesson plan, teachers will be able to select an engagement activity, identify follow-up activities, and allow time for gathering supplies needed by students to complete the lesson.

Execution time by module:

The following times are approximate. The execution time for each module could vary, depending on your purpose for using the module, the school's Internet location (e.g., classroom, library, computer lab), the number of computers available with Internet access, and the number of students in the class.

"Get to the Root of It" section
· Start with the basics — 30–60 minutes
· Light and color — 30–45 minutes
· Telescope design — 45–60 minutes

Explore the history of telescopes from Galileo to the Great Observatories
· Galileo’s Refractor — about 10 minutes
· Early Refractors — about 10 minutes
· Great Refractors — about 20 minutes
· Newton’s Telescope — about 10 minutes
· Early Reflectors — about 25 minutes
· Hugh Reflectors — about 20 minutes
· Solar Telescopes — about 10 minutes
· Radio Telescopes — about 15 minutes
· Multi-mirror Telescopes — about 15 minutes
· Space Telescopes — about 30 minutes

Physical layout of room:

Students can work in groups of two or individually in a computer lab. Adaptations can be made to accommodate classrooms with only a single computer with Internet access. This might include using an overhead projector with an LCD that projects the computer image on a screen or a hookup from a computer to a television monitor.

You can also complete "Telescopes From the Ground Up" off-line. Various software programs provide off-line access to the Internet. Their programs allow you to save Web pages to your local hard drive. Using your Netscape browser, you can open the Web pages locally and experience the lesson as if you were viewing it on the Internet. Using this option, however, will deny students access to the references (identified in the Grab Bag pages) available on the World Wide Web.


This lesson requires a computer with a color monitor and Internet connection. Your computer must be at least capable of running one of the following Web browsers: Mozilla, Firefox, Internet Explorer 5.5 and later on Windows, or Safari on Macintosh. For additional information read the Computer Needs section.

Procedure / directions:

This is a self-directed computer activity. Students may work independently or in small groups to complete the reading activity.

Suggested Engagement Activities:

1. Engage the students by having them view “Piercing the Sky,” a short audio slide show that introduces the main idea of this activity: that as telescopes advance, so does our ability to view and understand the universe.

· Computer with Internet connection
· LCD screen or large monitor
· url:

Instructions to the Teacher:
Have students divide a sheet of paper into two columns — one titled “know” and the other “would like to know.” To check for student misconceptions and set up a Level I inquiry activity, ask students to write down what they know about telescopes in the first column and what they would like to know in the second one. Collect their papers and compile a list of misconceptions the students display in their writing and/or poll the class to gauge their level of knowledge about telescopes and their history. There is a section in this lesson plan that addresses common misconceptions. View the audio slide show and discuss the relationship between advances in science and technological advances.

Instructions to the Student:
After setting up your paper as directed by your teacher, write down what you know about telescopes in the first column and questions you have about telescopes in the second column. Then view the slide show and check whether the things you know and/or the questions you wrote were topics addressed in the show. Be prepared to discuss the relationship between advances in scientific understanding and technological advances.

2. Engage the students by asking them to compare three images of the Whirlpool Galaxy, also known as M51, made using different telescopes. Students compare the images and speculate on the different technologies that made each possible.

Three images of the Whirlpool Galaxy, found in the image section of the Grab Bag.

Instructions to the Teacher:
Show students the three images of the Whirlpool Galaxy: one drawn by Lord Rosse, one taken by a telescope on Kitt Peak, and the third taken by the Hubble Space Telescope. Ask them to compare the images. Students should be encouraged to find similarities as well as differences among the images. Then ask students to speculate on the technologies that were used to produce these images and how each image has advanced science.

Instructions to the Student:
Look at the three images of the Whirlpool Galaxy, M51, and find similarities as well as differences among the images. What kinds of technologies would have been needed to make the images? How do you think each image has advanced science?

Step-by-step Instructions:
This is a self-directed activity. Each student can work independently, or groups of students can work together. The activity is flexible enough to fit almost any computer configuration at school or at home. “Telescopes From the Ground Up” consists of 10 eras, with at least one telescope associated with each era. The activity exposes students to the development of telescopes. Discoveries made with telescopes provided the motivation to build bigger and better telescopes. Knowledge about the science of light, lenses, and mirrors allowed the development of technology that facilitated telescope evolution. Teachers may want to assign students to learn a portion of the material and then share their learning with the other students in the class. Small groups of students can share their knowledge through a jigsaw- type activity, or the students can make formal presentations to the class. Additional features of the activity include biographies of scientists that are associated with specific telescope stories and science concepts accessed from either the stories or from the home page.

Students unfamiliar with the concepts of refraction and reflection, or how lenses and mirrors form images, may benefit from accessing the science concept graphics prior to reading the telescope stories. The science concepts can be accessed from the “Get to the root of it” link shown on the home page of the activity.

"Telescopes From the Ground Up" is composed of the following sections:

Era stories:

Galileo's Refractor: Galileo's telescope revealed the first hint of the depths of space. His dedication and approach to explaining what he saw revolutionized astronomy. (Includes one telescope story, one biography.)

Early Refractors: Telescopes with flatter lenses brought wider and clearer views of the sky but required longer tubes. Some refractors were so long that they became difficult to maneuver. (Includes two telescope stories.)

Great Refractors: New technology allowed astronomers to create larger lenses that produced bright, clear images. For a while, refracting telescopes became more popular than reflecting telescopes. (Includes three telescope stories, one biography.)

Newton's Telescope: Sir Isaac Newton replaced the main lens of a telescope with a mirror, creating the reflecting telescope. (Includes one telescope story.)

Early Reflectors: Early reflecting telescopes used metal mirrors to look deep into space, but the new design presented new challenges. (Includes four telescope stories, one biography.)

Hugh Reflectors: Astronomers crafted telescope mirrors from glass instead of metal, making reflecting telescopes more powerful and easier to use. They began relying on photography and instruments to record observations. (Includes three telescope stories, two biographies.)

Solar Telescopes: Solar telescopes are reflecting telescopes that use special instruments to observe the Sun. (Includes one telescope story, one biography.)

Radio Telescopes: The discovery of radio waves from space launched a new branch of study: radio astronomy. This spurred astronomers to develop new techniques to accommodate the large size of radio waves. (Includes two telescope stories.)

Multi-mirror Telescopes: Multi-mirror telescopes used computer technology to overcome the size limits of huge reflecting telescopes. (Includes two telescope stories, one biography.)

Space Telescopes: By placing telescopes in orbit above Earth, astronomers were finally free to view the universe in all wavelengths of light. (Includes five telescope stories, two biographies.)

Biographies of scientists/astronomers can be accessed from the stories. Examples include Galileo Galilei, Caroline Herschel, Annie Jump Cannon, Edwin Hubble, George Ellery Hale, and Lyman Spitzer Jr.

Statements of significant discoveries accompany each telescope and appear with the telescope image for each story.

Get to the Root of It:
This section of the activity contains science information about light, lenses, mirrors, and telescopes. Teachers may wish to begin the activity by having students work through this section to prepare them for the science content they will encounter while reading the era and telescope stories.

Evaluation / assessment:

The assessment activity “Telescope Timeline” and an answer key are available in the “Downloadable Documents” section of the Grab Bag. In the activity, students are asked to read and analyze the era and telescope stories so that they can determine the order and significance of major events and/or discoveries in the evolution of telescopes. This assessment should be available to the students as they work through the activity.

One-computer classroom:

It is recommended that teachers project the images from the computer onto a classroom screen using an overhead LCD or a television screen. Here are two suggestions to facilitate a large group presentation and to avoid last-minute glitches, which can always occur when using the Internet. First, bookmark the part of the lesson you wish to use and download it onto your hard drive. This will eliminate the inconvenience of the Internet unexpectedly going off-line. A second suggestion is to print and duplicate selected parts of the lesson from the "Grab Bag" and distribute them to the students.

Classrooms without computers:

Here are some suggestions:

· If your school has one or more computers located outside your classroom — for example, in a library or a computer lab — students, either independently or in small groups, may experience the lesson as a learning station or as a supplement to your technology unit.
· Some students may have computers at home with access to the Internet. If that's the case, you might consider assigning the "Telescopes From the Ground Up" lesson as homework or as extra credit.
· Your closest NASA Field Center Educator Resource Center offers free NASA lithographs and posters featuring the Hubble Space Telescope and its images. They can be used as teaching tools in the classroom.

Home schooler:

This lesson is easily followed without additional teacher support if the prerequisites are met. Parents can preview the lesson and examine the teacher pages ahead of time. A wealth of information can be found in “Capture the Cosmos” on the Amazing Space web site at In addition, images from the Hubble Space Telescope are available in NewsCenter at

More information for the home-schooled can be found at:

Send your comments about this page to: