Watching the Stars by Eye – People have been viewing the stars since long before any technology was invented. The earliest use of the stars was for things like crop planning. Different stars are visible at different times of year, allowing farmers to know what exactly when they should plant crops.
The first navigational use of stars was also by eye. Sailors noticed that all the other stars circled around Polaris, the North Star. The height of Polaris in the sky is an accurate measurement of how North or South the viewer is. Sailors would use a string with a knot in it representing their home port. Holding it a certain distance from the eye so the end of the string was on Polaris, they would look at how close the knot was to the horizon. If it was exactly on the horizon, they simply had to sail east or west to get home. If it was not, then they would sail North or South until it was.
Navigating With the Quadrant and Sextant
The quadrant was invented to make measuring the height of a star, and therefore a ship’s latitude, a simple process. It was basically a protractor with a weighted string attached. The quadrant would be angled so that it pointed at Polaris, and the weight would hang down, marking what angle the quadrant was tilted at.
The sextant is a more precise improvement of the concept using mirrors and optics to achieve a more precise result.
The invention of the first telescope is attributed to Galileo. It uses a pair of lenses to capture the light hitting a large area and condense it to a small area that a human eye can view. This allows faint lights to be concentrated so they can be more clearly seen, and it also enlarges whatever is being viewed.
Galileo’s telescope used lenses, which are hard to accurately scale to the sizes used by modern telescopes, but the design is still common in binoculars and small scopes.
Tycho Brahe was an interesting man. He had a prosthetic nose and a pet moose. He also happened to be an important astronomer. He didn’t invent any new mechanisms for measuring the stars, but he did fund the construction of massive tools, much larger than anything built at the time. With astronomy, bigger is better, providing more accurate results. His observatories helped build incredibly accurate tables of the movements of planets, leading to many later discoveries.
The Hubble Space Telescope
The Hubble Telescope takes everything we know about telescopes and makes it bigger and in space. Because of the problems with large lens-based telescopes it uses curved mirrors instead. It is in space, so cloudy days and atmospheric distortion aren’t a problem, allowing round-the-clock observation. It can take pictures of such faint objects that it has observed galaxies over 12 billion light years away. It took that light 12 billion years to reach the telescope, so the universe was very young when it left. These observations have helped scientists learn about the early history of our universe.