DIY Homeschooler

Astronomer Edwin Hubble was born November 20, 1889. He is best known for proving the existence of galaxies besides our own. With his work, astronomers realized that the universe is significantly larger than previously thought.

Hubble reached this discovery using some of the largest telescopes of his time. In light of all this, what could be more fitting than that the best telescope the world has ever seen be named after him? The Hubble Telescope is used for exploring the far-away galaxies that its namesake discovered.

Table of Contents

• The History of the Telescope
• The Challenges in Telescope Design
• The Hubble Telescope
• Hubble Trouble
• Suggestions

The History of the Telescope

Telescopes were first invented by Hans Lipperhsey, although credited to Galileo. Lippershey’s telescope was a refractor telescope with two lenses: a convex objective lens and an eyepiece, concave in shape. Galileo used this type of telescope one year later in 1609.

Newton designed the reflector telescope in 1668. His telescope used a mirror to reflect and concentrate light onto another mirror. The new focused image was sent to an eyepiece on the side of the telescope housing.

A later design placed a mirror in the middle of the telescope, reflecting the image back towards the main mirror. This mirror had a hole in the center, allowing for an eyepiece at the end of the telescope.

Significant improvements were still made, but were generally on the order of increasing ease of use. The mirrors used in reflector telescopes were improved by using reflective coatings that didn’t tarnish. The more accurate grinding of lenses and mirrors also helped significantly.

The Challenges in Telescope Design

Resolution has always presented a problem in design. Longer telescope lengths can be used to remedy this problem. The drawback being that they can make the telescopes rather unwieldy and unstable.

Better frameworks fixed the stability problems. The use of reflector telescopes also aided the situation. Reflector telescopes can be manufactured shorter than refractor telescopes.

A point is reached where further increase in telescope resolution is pointless; the atmosphere limits resolution as it is practically a dirty lens in its own right. Now if only one could raise the telescope above the earth’s atmosphere….

The Hubble Telescope

This dream was realized with the advent of space travel. The idea for a telescope, called the Hubble Telescope, was formed. The Hubble would provide increased resolution and range by being placed above the pollution and clouds of the atmosphere. It would send the information gleaned to earth via radio waves.

The telescope itself was to be of the Ritchey-Chrétien design — a reflector telescope with two concave mirrors reflecting light back through the center of the telescope main mirror. The design was proposed in 1905. It differed from other designs in as much as there were two magnifying convex mirrors instead of one convex and another regular flat mirror to direct the light where desired. The images of stars, for example, would be rounder. Coma problems were also remedied — the image is blurred and comet shaped — as well as spherical aberration.

The telescope cost more and took longer to build than anticipated. It was finally launched in 1990. Unfortunately the spherical aberration was not been eliminated.

Hubble Trouble

A Ritchey-Chrétien telescope requires special instruments called null detectors to test the curvature of the mirror. The manufacturer of the main Hubble mirror had used a custom-made null detector for the purpose. Unfortunately, they had assembled it wrong — a lens was off by 1.3 mm. This of course introduced error.

The manufacturer also tested the mirror with conventional null detectors as well as their custom-made one. These did show a flaw, but the company chose to ignore the results concluding that their custom null detector was more accurate. Either way, the Hubble telescope was none too useful, and it needed fixed.

The only practical solution was to install a “COSTAR” — a bank of corrective optics. The solution was installed in space, and worked quite well. Eventually it was replaced with sensors designed to compensate for the error in the main mirror.

The Hubble telescope proved to revolutionize the world of astronomy, making gazing into the other galaxies Edwin Hubble discovered easier and more fascinating.

Suggestions

Have your students do one or more of the following (resources to help follow below):

• Explore the stars.
• Compare/contrast a refractor vs. a reflector telescope.
• Explain the importance of the Hubble Telescope.
• Create a timeline of the telescope.
• Why did it need to be above earth’s atmosphere?
• Explore the Milky Way.

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Further Investigation

Edwin P. Hubble
Biography from NASA.

Telescope History (archived)
Follow the links at the left to view the entire timeline from Lippershey in 1608 through Hobby-Eberly in 1997.

Refractors (archived)
Explanation with diagram from the McDonald Observatory at the University of Texas.

Reflectors (archived)
Explanation with diagram also from the McDonald Observatory.

The History of the Hubble Space Telescope
From NASA.

A Chronology of the Hubble Space Telescope
Timeline from NASA.

Activities

Scope It Out!
Telescope game at NASA.

Telescope Simulator
Great interactive that helps you to see what happens when you use lenses of different focal length, different eyepieces, or other variations.

Build Your Own Refracting Telescope
Project from the National Solar Observatory aimed at Grades 6–8.

Make Your Own Telescope (archived)
Easy-to-make idea from the Exploratorium.

Summer Fun Activity: NASA Optics Educator’s Guide
More complicated plan from NASA for older students. Activity #15.

Simple Telescopes
Easy-to-follow explanation on how to make your own with diagrams.

Planetarium for Your Computer {Free}
Find out what is in the night sky so that you’ll know what to look for with your telescope.

Books

The New Astronomy Book by Danny R. Faulkner
Covers the basics of astronomy, the moon, the night sky, stars, planets, galaxies, comets, and much more. The Astronomy Book Study Guide

The Telescope by Thomas Nolan
Accessible public domain work explaining the construction of telescopes including the differences between reflecting and refracting telescopes.

Star Stories by Gertrude Chandler Warner
Free eBook download to help young ones become familiar with the constellations. Link includes free Star Book download.

Unit Studies & Lesson Plans

Taking a Closer Look: Examining Light and Telescope
Great lesson plan at NASA adaptable to all grades with four activities covering how telescopes work. Worksheets with answer key and posters included.

How Telescopes Work
Lesson plan from the observatory at LSU that demonstrates the difference between reflecting, refracting, and compound telescopes.

Free Nature Studies: The Solar System
Lots of astronomy resources in this section of our free nature studies, including telescope and night sky helps.

Printables & Notebooking Pages

Hubble Space Telescope
Diagram for notebook.

Hubble Exploded
Parts diagram for notebook showing how it is assembled.

Telescope Notebooking pages
Simple pages for copywork, narrations, or wrapping up.

These units have been created specifically with do-it-yourself (DIY) homeschoolers in mind: those that don’t want a lot of hand-holding. If this doesn’t describe your need, you might prefer a few of these pre-planned units. For those brave souls who enjoy pulling things together themselves, there are many ways to use these resources!