A telescope is a chance to look into the universe

It's easy to guess that a telescope is an optical device designed to observe celestial bodies. Indeed, its main task is to collect the electromagnetic radiation radiated by the remote object and to direct it to the focus where an enlarged image is formed or an amplified signal is formed. To date, there are many different telescopes - from home, which can be purchased by anyone, to high-precision ones, such as the "Hubble", capable of looking at millions and billions of light years deep into the Universe ...

A bit of history

It is considered that the first appeared in 1609, a two-lens telescope was invented by Galileo Galilei. However, it is not. A year ago, the Dutchman Johann Lipsersgay wanted to patent his device, consisting of lenses inserted in a tube, which he called "telescope", but was refused because of the simplicity of the design.

Even earlier, at the end of the 16th century, astronomer Thomas Digges tried to observe the stars through concave mirrors and lenses. True, the idea was never brought to its logical conclusion. Galileo just turned out to be "at the right time, in the right place": he guided the Lippersgay pipe into the sky, he opened craters and mountains on the surface of the Moon and many other interesting things. That's why he is considered the first astronomer to use a telescope. This gave rise to the era of refractive telescopes.

Types of optical equipment

To subdivide optical telescopes into types can be based on the basic type of element that collects light on mirror, lens and mirror-lens (combined) devices. Each of these types has its own advantages and disadvantages, so when choosing a suitable system, several factors need to be taken into account: conditions and objectives of observations, requirements for dimensions, weight and transportability, price, and so on. Let's try to understand in more detail what a telescope is, and what are the main characteristics of its most popular types. So, what does the telescope look like?

Refractive lens telescopes

In these telescopes are used to approximate the lens, which due to its curvature collect light. As well as in other optical devices (cameras, microscopes, etc.), all lenses are assembled into one device - the lens.

At present, refractory telescopes are used mainly by amateurs, since they are calculated for observations only on nearby planets and the Moon.

Pluses:

• Relatively simple design, reliability and ease of use.
• Does not require special maintenance.
• Excellent color rendering in apochromatic performance and good in achromatic.
• Remarkably suitable for observing double stars, planets, the Moon, especially for large apertures.
• Fast thermostabilization.
• The lens does not require adjustments, as it is adjusted by the manufacturer even during production.

Disadvantages:

• Compared with katadioptrikami and reflectors, have a higher cost per unit diameter of the lens.
• The practical maximum diameter of the aperture is limited by the price and cumbersome.
• Due to limitations on the aperture, refractors are generally less suitable for observing distant, dull objects.

Mirror telescopes-reflectors

The reflective telescope is an optical device, in which the function of a light-collecting lens is performed by a mirror. The main mirror can be small diameter (spherical) or large (parabolic).

Pluses:

• Compared with katadioptrikami and refractors, the cost per unit diameter of the aperture is lower.
• Compact and convenient for transportation.
• Due to the relatively large aperture, they work remarkably for observations of distant and dim objects: star clusters, nebulae, galaxies.
• No chromatic aberration. Images are bright, with little distortion

Disadvantages:

• Thermostabilization takes time, because of the massive glass mirror.
• The image is slightly distorted due to an open pipe, unprotected from warm air and dust.
• Periodically, the alignment of mirrors is required, which can be lost during operation or transportation.

Mirror-lens, or catadioptric

A catadioptric telescope is an optical device in which various kinds of image distortions are minimized by using mirrors in them together with correcting lenses. Due to the fact that the light inside the tube is reflected several times, the focus can be long. Some models are capable of capturing an image. If we use a catadioptric telescope for this purpose, the photos will be of quite good quality.

Pluses:

• Correction of high-level aberrations.
• It is great for observing both close objects, such as the Moon, and behind objects in distant space.
• Closed pipe maximally protects from dust and warm air currents.
• Compared with reflectors and refractors with the same aperture, the greatest compactness remains.
• In comparison with the refractor, the cost of large apertures is much lower.

Disadvantages:

• Relatively long thermostabilization.
• The cost of an equal aperture is greater than that of reflectors.
• Self-alignment is difficult due to the complexity of the design.

Modern space telescopes

Having gone a long way (starting with the telescope of the XVII century and ending with automatic space giants), the telescope opened up huge opportunities in the study of the star sky. But there are many factors that prevent anyone, even the most powerful ground-based telescope, from conducting research. These can include both exposure and turbulence, and the most banal clouds. Orbital space stations in this regard have a huge advantage, because they are able to work around the clock, in any weather conditions, transmitting images without the slightest atmospheric distortion. One such station is the Hubble Space Telescope. Photos made by his optics perfectly reflect the most remote objects of the universe, removed by billions of kilometers, allowing astronomers to discover new stars, planets and galaxies.