Hobbies And Interests
Optical Telescopes
An optical telescope collects light using a lens or a mirror so that the details of the image can be magnified. As the lens or mirror increases in size, so does the amount of light that is collected. As more light is collected, the image gains more detail.
Three types of optical telescopes are used: the reflecting telescope, the refracting telescope and the catadioptric telescope. Reflecting telescopes use a concave mirror, reflecting surface bulges inward to collect and focus light. A refracting telescope uses objective lenses that collect light, using the lenses, to bring the light to a focal point. The catadioptric telescope combines mirrors and lenses to collect and focus light. Mirrors for reflecting telescopes can be very large, which offers a major advantage for gaining details of stars.
Radio Telescopes
Radio telescopes collect radio waves from stars. Radiation from a star is reflected to an aerial, called a dipole, that is at the focus of a parabolic dish. The signals are then transferred to a radio receiver. A series, or array, of antennae are spaced equally apart to increase the resolution of the observation. Radio telescopes help determine the elevation angle of stars.
Infrared Telescopes
Most of the infrared radiation from space is absorbed by the atmosphere before it reaches earth. Large infrared telescopes are built in satellites orbiting earth, are installed in high flying aircraft or are placed on mountain tops to get the best infrared signals. Infrared telescopes must distinguish between the infrared radiation coming from the star and all of the radiation coming from other objects. Everything that produces heat produces infrared radiation, including the infrared telescope itself. The infrared telescope uses special film or imaging sensors to distinguish the radiation and must be consistently cooled to avoid infrared interference.
High Frequency Observations
High frequency radiation gets absorbed by the earth's stratosphere. Ground-based instruments cannot collect it. High frequency radiation is collected and studied using instruments on satellites, spacecraft or high-altitude balloons. High frequency radiation includes ultraviolet light, X-rays and gamma rays. X-rays cannot be collected by conventional mirror telescopes because mirrors absorb X-rays. Grazing incidence telescopes which collect X-rays by reflecting them at shallow angles are used to collect X-ray information. Because gamma rays are so small, they cannot be focused when reflected by a mirror. Scintillators are used to convert gamma rays into visible light that can be analyzed. Astronomers collect high frequency radiation information from stars to gain additional details about them, such as orientations of clusters, clouds of gasses and hot and cool areas that they would not otherwise observe from optical or infrared light sources.