Telescopes make things appear clearer and brighter by collecting the light that bounces off objects. Light exists in lots of different wavelengths which make up what is called the electromagnetic spectrum. Astronomers have special telescopes to collect each kind of light. This enables them to look deeper into the mysteries of space. Learning how to use a simple telescope allows anyone to experience the wonders of planets and stars.
Types of Telescopes
An optical telescope gathers light from the visible part of the spectrum, which is quite small. If the whole electromagnetic spectrum was represented by a piano keyboard, the visible portion would take up only one key. Optical telescopes can be refractors, which have a lens at the front to collect and focus light; or reflectors, where light is gathered and focused by a rear mirror. Catadioptric telescopes have both a mirror and a lens.
Radio telescopes, such as the Aricebo Telescope in Puerto Rico, use a huge mirror which reflects radio waves to special detectors hanging above. Although it is used to view distant galaxies, a single radio telescope cannot produce very sharp pictures of objects in space. In order to obtain detailed, focused images scientists combine signals from a number of different radio telescopes, effectively creating one enormous super-telescope. This produces sharp pictures similar to those seen with an optical telescope.
X-ray telescopes are located in orbit because the Earth's atmosphere blocks X-rays. As X-rays travel through things, they tend to travel through the mirrors inside telescopes. In order to prevent this, X-ray telescopes have mirrors placed at shallow angles so that the rays only just graze them instead of passing through. NASA's Chandra is one of the largest X-ray telescopes in orbit. It has been used to view sights such as supernovas and galaxies colliding.
Like X-rays, gamma rays cannot travel through the Earth's atmosphere. Gamma-ray telescopes are sent into orbit, but it is also possible to see the effects of gamma rays from Earth. Tiny particles are produced when gamma rays hit Earth's atmosphere and collide with air molecules. Gamma-ray telescopes on Earth detect these particles and they can be used to build up a picture of the gamma rays themselves. Astronomers can use gamma-ray telescopes to look at unusual sights such as black holes.
How to Use a Telescope
Set up the tripod so that it does not wobble. Fix the telescope to its mount and extend the tripod legs if needed. Using a low-power eyepiece, aim the telescope at a bright star. There should be a small finderscope attached to the main telescope. Adjust its position until the star is centered in both the finderscope crosshairs and the telescope. Repeat these steps with a high-power eyepiece. Try to set up in a location away from city lights when the sky is clear. Use a sky map to discover which constellations are visible at different times of the year.
Telescope Care and Cleaning
Unless the telescope is in use, keep the cap on the lens, and store the eyepieces away from dust inside their containers. If dust settles on the glass parts, remove it with a lens brush. Avoid cleaning the objective lens too often as this will alter its shape. When cleaning becomes necessary, use a clean cotton swab dipped in alcohol. If moisture condenses on the telescope allow it to dry naturally in a warm place before putting it away.
It is dangerous to look at the sun through a telescope, but the moon in all its detail can be a fascinating sight for a beginner. Jupiter and its moons can be seen even with a small telescope. Mars and Venus are worth viewing, as is Saturn with its spectacular rings. The Orion Nebula and the star clusters of the Hyades and Pleiades are also good choices for the new astronomer.
Tips and Tricks
Use sky maps, books and field guides to help plan what to look for. It takes time to see things well through a telescope, and making sketches can help to train the eye. Set up on a clear night, away from light pollution, and using low magnification. Planets are easier to see when they are high over the horizon and the moon when it is less than full. Depending on location, different stars and planets may be seen at different times of the year. A star chart or an astronomy website can provide information about what should be visible and which are the best viewing times.