telescopes that don't use visible light

Telescopes That Don’t Use Visible Light

When we think of the best telescopes, we often conjure images of long tubes with lenses and mirrors. People peek into an eyepiece and they see wonders from a great distance. Although designs vary, the main principle remains the same. Optical telescopes gather light, create a focused image, and magnify this to see impressive detail. Despite their proven effectiveness, they have serious limitations that pushed scientists and engineers to invent non-optical sky trackers or telescopes that don’t use visible light. Instead, these new equipment utilize other parts of the frequency spectrum to reveal different characteristics of heavenly bodies.

Why Use Telescopes that Don’t Use Light?

1. They can be used during the day.

Optical telescopes can’t be used at night because the stars are not visible. The intense brightness of the sun overpowers their faint lights. This means they are idle half the time or even more. Observations are limited and equipment can’t be optimized. If you can have a scope that does not depend on light, then it may be possible to track the sky objects around the clock. This not only improves operational efficiency, it also makes it possible to monitor movements on a continuous basis such that there are no gaps in data.

2. They can work despite bad weather and atmospheric turbulence.

Another challenge to optical telescopes is the onset of bad weather conditions. If the sky is cloudy because of imminent rain, then there is simply nothing to see up above except for lightning and perhaps the moon. One would also be concerned about exposing sensitive equipment to heavy rainfall and snowfall. The clouds of ash from a volcanic eruption can also darken the skies for days or weeks within the vicinity. In urban centers, the presence of bright lights below can also interfere with observations. Other types of higher level atmospheric turbulence can also prevent them from being utilized. Non-optical telescopes can see through clouds and other barriers.

3. They can be smaller and cheaper to build than comparable optical telescopes.

Building small optical telescopes for hobbyists is easy. A lot of manufacturers cater to this segment such that backyard astronomy is enjoyed by millions. That is not the case for massive telescopes that require gigantic mirrors and lenses. Fabricating these to the exact specifications and quality standards is something that only a few companies are capable of. Naturally, this means the price is also incredibly high. Transporting and handling these optical components safely is also a big headache. It is possible to get comparable results using non-optical telescopes with smaller size and lighter builds.

What Non-optical Telescopes Use Instead of Visible Light

Radio Waves

In the 1930s, it was discovered that some of the short-wave radio interference experienced across the Atlantic came high up from the sky. In fact, it was coming from the center of our Milky Way galaxy. Since then, people have been building radio telescopes to detect these emissions from outer space. They usually have a large parabolic dish made of metal mesh or sheets. A receiver is located at the focal point to collect the signal which is then amplified and analyzed by a computer. The signals under observation range from 30MHz to 600GHz such that the wavelengths are from 10m to 0.5mm. Arrays of radio telescopes are used to improve resolution.

Infrared Rays

These function much like reflector telescopes. Infrared rays are collected by a primary mirror which reflects it to a secondary mirror that focuses everything onto a detector. The image is then recorded, processed, and analyzed. These need to be cooled down significantly to avoid heating up and producing their own infrared waves that might introduce noise to the data. They also need to be located in dry regions such as deserts where there is little water vapor in the atmosphere that could block infrared radiation. They are small enough to be placed on balloons, planes, and satellites. These IR telescopes work well for observing planets, nebula, and brown dwarf stars.

Ultraviolet Rays

UV telescopes, on the other hand, work in a similar way to refractor telescopes. Any incoming waves go through a mirror and sent directly to the detector. Sometimes there is a secondary mirror that acts as the bridge. Since UV radiation can get absorbed aby the moisture in the atmosphere, these telescopes are usually placed on satellites where they can collect data from high above. Their small size makes this possible. They are excellent tools for studying the formation of stars. However, they have stringent requirements for mirror quality as even the most minor imperfections and impurities can drastically affect the data.


X-rays are a different beast which require unique handling. Using parabolic reflecting mirrors will not work because the rays would just pass through. Instead, they need mirror arrays with shallow angles that can deflect the rays gradually until they reach the detector. With the long focal length, the telescope must be several meters long. Just like UV scopes, these will need to hitch a ride on satellites since X-rays can’t pass through the Earth’s thick atmosphere. They have to be high enough to detect the signals. Astronomers feel that this is worth the effort since the equipment allows them to study the distribution of hot gases in remains of supernova and determine the composition of the universe.

Gamma Rays

Most of the gamma ray telescopes are also in orbit. They are used to monitor supernova explosions, black holes, pulsars, and gamma ray bursts. These are phenomena that are difficult to detect with other forms of telescopes as they require focus on a certain wavelength. These rays have high energy and don’t require focusing so they tend to be smaller than other scopes. They can come from any direction so it is necessary to shield from unwanted directions so as not to muddle the data.

As you can see, telescopes that don’t use visible light are extremely useful. They have their own quirks and special abilities so using them the right way is essential.

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