Types of Telescopes/Observatories
The range of types of telescopes and observatories is quite diverse. Each type is dedicated to detecting and measuring a particular wavelength and frequency range on the Electromagnetic Spectrum. The most common is the optical telescope which measures the visible wavelengths that we humans are capable of seeing. Visible wavelengths are directly identified with colors.
However the visible wavelengths represent only a very small portion of the EM spectrum. Today we have telescopes that measure X-rays, Gamma rays, and Ultraviolet rays, all of which have shorter wavelengths and higher energies than the visible waves. In addition there are telescopes that measure infrared and radio waves. These latter have longer wavelengths and lower energies than the visible waves. Earth-based telescopes can measure the optical, infrared and some radio waves. The higher energy waves are only detected by telescopes on orbiting satellites, since those waves cannot penetrate the earth’s atmosphere.
One further significant piece of information about the earth-based telescopes: Optical and infrared telescopes use large mirrors to receive and focus the incoming waves. Older optical telescopes use large lenses. Radio telescopes use dish antennas for the same purpose.
If you are wondering why we have telescopes that detect different wavelengths, other than light waves, the following is a very brief explanation: Although we humans can only see what we call visible light or visible waves, there is so much going on out there in the Universe that we cannot see. Those processes (black holes or star formation are examples) emit energies/waves that cannot be detected by optical telescopes. However many of these other telescopes can see those waves, and, in so doing, they give us much more information about what is happening out there.