Telescopes are an important tool in astronomy, which is the science of viewing and analyzing space objects. Refractors, reflectors, and catadioptrics are the three most common types. An astronomical telescope is a device that uses mirrors, lenses, or a combination of the two to view objects in space beyond Earth’s atmosphere.
The earliest designs were refractor telescopes, which were invented in the early 1600s. They collect light at one end, known as the objective, and create a visible image at the other end, known as the eyepiece. Refractors can collect more light by using larger lenses, and increasing the length can increase magnification, but the size of refractor designs has practical limits. The largest objective lens produced had a diameter of 40 inches (1.02 meters) and a length of 68 feet (21 meters).
Reflectors are a type of astronomical telescope that uses mirrors to collect, focus, and direct an image to an eyepiece. An objective curved mirror reflects the light to the barrel’s center, where it is reflected sideways to an eyepiece by a second mirror. A single ground glass mirror, a combination of smaller mirror segments, or non-metallic materials with reflective coatings can all be used as the objective mirror.
By altering the curvature of the objective mirror, reflectors can collect more light without lengthening. Amateur astronomers who require portable equipment will find them useful. An automobile can accommodate a large number of reflectors with good image resolution.
A catadioptric telescope is the third type of astronomical telescope. This design is a hybrid of a reflector and a refractor. They are shaped like reflectors and have a mirror as their objective. Refracting lenses sharpen the image while minimizing distortion caused by mirror flaws.
Imperfections in the lenses or mirrors of any astronomical telescope cause viewed images to be unfocused or have color differences. The edges of a mirror or lens may refract or reflect light in a slightly different direction than the rest of the light. This is referred to as spherical aberration, and it results in distorted images.
Chromatic aberration is another flaw, which is caused by different wavelengths of light passing through a lens at different angles. This can cause the viewed image to have incorrect colors or colors that differ from the center to the edges of the viewing field. Both types of aberration can cause image distortions, which can make it difficult to investigate new astronomical discoveries scientifically.
The size of the objective lens or mirror, the magnification power, and the materials used in the construction of an astronomical telescope are all factors to consider when designing one. Reflectors were first made with groups of smaller mirrors in the early twentieth century, some with electronic controls that allowed individual mirror segments to move independently. All of these designs were aimed at reducing the aberration effects of larger fixed mirrors in order to improve image resolution.
Wavelengths outside the visible light spectrum can also be investigated, primarily through reflector designs. It is possible to see infrared light (light that is below the red light spectrum) and ultraviolet light (light that is above the blue light spectrum). Electronic image sensors, rather than eyepieces, can be used to collect radio waves from space with radio telescopes.
VLA systems are groups of radio telescopes separated by a significant distance. Each unit serves as a personal reflection of a much larger virtual unit. The VLA signals are processed in computers to create an image that is the size of a telescope many miles or kilometers across.
The atmosphere causes distortion in Earth-based telescopes as well. Many are erected at the summits of mountains or on the craters of extinct volcanoes in an attempt to reduce distortion. The Hubble space telescope, which was launched into orbit in April 1990, was the first design to be deployed in space. Despite some mirror flaws that were corrected in later repair missions, Hubble has returned a large number of atmospheric-free astronomical images.