He first picked up the pursuit of astronomy as a hobby.  It quite possibly would have remained just a hobby but on one night in 1781 he discovered the planet Uranus and this discovery brought him a lot of fame and enough fortune to give up his normal job as musician. He went on to study astronomy and telescope making full time. He became so enamored by it and by the art of telescope making that he rose to the position of Kings Astronomer and during his lifetime he made telescopes and discoveries of celestial objects that shaped much of the modern science and pursuit of astronomy.

He was born in 1738 and he lived until 1822. During this time he and his sister Caroline devoted many hours and many nights to observing celestial objects and making ever larger telescopes.  His largest telescope was larger than a house, and while it was quite a remarkable instrument, it was cumbersome to use so he used a smaller telescope that was only twenty feet long for most of his serious discoveries and observations.

Some of Herschel’s Discoveries and Accomplishments

·         He discovered a new planet (Uranus) in 1781

·         He built the largest telescope of his time

·         He discovered two satellites of Uranus

·         He discovered two moons of Saturn (Mimas and Enceladus)

·         He discovered two new moons of Jupiter (Titania and Oberon

·         He coined the word asteroid from the Greek

·         He created an extensive catalog of nebulae called the Herschel Catalog which has over 2,500 listings

·         He discovered that most double stars were not optical doubles but actual binary stars that revolved around each other. This was significant because it was the first proof that Newton’s law of gravitation applies to objects outside our solar system.

·         By observing the motion of stars he also discovered the fact that our solar system is moving in space.  And he determined in which direction it is moving.

He built most of his telescopes and used them at his home in Bath England and to this day the home still stands and has been turned into a museum that the public can visit. It is called the Herschel Museum of Astronomy.

His sister Caroline spent many years as his assistant and she would take extensive notes while he observed through the telescope. Eventually she began making observations on her own and became quite a famous astronomer in her own right. She is credited with making many discoveries including eight comets and the M 110 Galaxy which is the second companion galaxy to the famed Andromeda Galaxy.

William Herschel lived in a time when it was not possible to simply buy a telescope. He was forced to build his own. Because of this he advanced both the science of astronomy and the art of telescope making. His largest telescope was the largest in the world for almost 50 years.  Eventually technology improved and it allowed other people to make even larger and better telescopes. Nevertheless Herschel holds a special place in the worlds of astronomy and telescope making as the greatest telescope maker of the 18th century and as one of the greatest observers of all time.

William Herschel and the Biggest Telescope of the 18th Century is a post from: Meade Telescopes

The largest Refractor telescope

Refractor telescopes are renowned for their absolute sharpness of image because they are composed of very large lenses of compounds of glass which gives them crystal clear images. But they are extraordinarily difficult to make in a large size. Their own weight distorts their shape and makes them unusable above a certain size.

The largest refractor in the world is the Yerkes telescope which has a primary lens that is 40 inches in diameter.  It was completed in 1897 and was built by the famous master optician Alvan Clark. It represents the pinnacle of refractor telescope making and no larger one has since been built in the hundred years since. Reflectors are much more feasible for larger sizes and there are many of this type that are extraordinarily large. It is with reflectors that we achieve very large instruments.  

Reflector telescopes come in two different types. The first type is the single mirror type where a single piece of glass is cast and polished to make the primary mirror. The second type is the segmented mirror where a series of hexagonal mirrors are assembled together into a single large mirror. This type of mirror looks much like the honeycomb from a beehive and this new technology is allowing telescope makers to make instruments larger than ever imagined.

The largest single piece of glass telescope in the world is the Large Binocular Telescope (LBT) in Arizona. It is a telescope composed of two separate mirrors that are side by side and work in tandem. The light from both of them are blended into one single image. Each mirror is 8.4 meters (330 inches) in width and when used together they create the equivalent of a mirror that is 11.8 meters (464 inches) across which is currently the largest light collecting size on Earth. It is located in Mount Graham International Observatory in Arizona.

Segmented mirrors pose technology challenges that have been overcome in the past decade and now these multiple mirror scopes are being built in extremely large sizes that cannot be rivaled by single piece mirrors. Of the segmented telescopes where a series of honeycomb shapes are assembled together into a single telescope there are three different observatories with these largest of mirrors.

The South African Large Telescope (SALT) is the largest primary mirror scope in the world and it has a segmented mirror that is 11 meters (433 inches) across.

The Gran Telescopio Canarias or GTC is located on the island of LaPalma Spain and it has a segmented primary mirror that is 10.4 meters in diameter (409 inches) which makes it the single largest mirror in the world.

The Keck Telescopes are a pair of telescopes located at the Keck Observatory in Hawaii. Each mirror is ten meters (400 inches) in diameter.

Bigger Telescopes to come

There are even larger telescopes currently in the proposal, development, or construction stage.  Technology improvements over the past decade have made a new scale of telescope possible and this new scale is referred to as ELT or Extremely Large Telescopes and it is the next generation to come.  ELT’s are telescopes that are more than twenty meters in diameter which is double the size of existing telescopes.  And this doubling of size gives significantly more than double the light gathering power. Most of these scopes will be of the segmented mirror type but one notable exception is the Giant Magellan telescope which will be composed of seven spherical mirrors constructed together so they act as a single mirror.  This project is scheduled for completion in 2016. It will be located in Las Companas Observatory, Chile.

The Thirty Meter Telescope (TMT), which is currently in development, will be thirty meters across and composed of segmented mirrors.  It is expected to be a telescope of unmatched performance and is predicted to be able to image planets circling other stars.  The current time line for this project is for it to be completed somewhere around 2017 – 2018.

What about the Famous Hubble Telescope?

The primary mirror in the Hubble is 2.4 meters across (94.5 inches) which makes it rather small compared to some of the giants listed in this article. So then why is it the most spectacular telescope ever created? The big advantage the Hubble has over all the other telescopes is that it doesn’t have to peer through the soup of Earth’s atmosphere.  And this advantage is staggering.  That is why the Hubble has brought us some of the most extraordinary images ever recorded.

What comes after the Hubble?

NASA is currently working on its next generation space telescope. It is called the James Webb Space Telescope (JWST). The primary mirror will be 6.5 meters (21.3 feet) in diameter.  Launch is planned for 2013.

Since the invention of the first telescope 400 years ago man has been building ever larger telescopes. The telescopes to come will bring us images of planets around other stars and who knows, they may bring us images of the very birth of the universe we live in.

A Look at the Biggest Telescopes in the World is a post from: Meade Telescopes