Different Kind of Telescope

Most people are very familiar with a telescope and its main function of viewing objects at a very far distance, but do not realize that there are various kinds of telescope. The most common known telescopes are the optical telescopes and they are the one used to view objects at a great distance. Some common telescopes to look at stars and planets from Earth are the refracting telescope, reflecting telescope, and catadioptric telescope.

Diagram of Galilean telescope: y - distant object; y' - real image from objective; y'' - magnified virtual image from eye piece; D - entrance pupil diameter; d - virtual exit pupil diameter; L1 - objective lens; L2 - eyepiece lens, virtual exist pupil

Once of the very first optical telescope is the Galilean telescope with involves using the objective lens and a divergence eyepiece lens to produce an upright image. Although there are many flaws in the designs, but the telescope is still good in observing stars and planets. Despite its blurry and distorted images, the telescope set a path for better telescopes.

Taken by the Spitzer Space Telescope, it is the Helix Nebula. Blue show infrared light of 3.6 to 4.5 micrometers; green shows infrared light of 5.8 to 8 micrometers; and red shows infrared light of 24 micrometers.

The there are the space telescopes. These telescopes are the ones that orbit by a Space Shuttle in low Earth orbit. Some of their main functions include observing in near ultraviolet, visible, and in near infrared. They share much similarity to the optics telescope, but operate in space instead. Some famous telescopes include the Spitzer Space Telescope and the Hubble Space Telescope.

World's Largest single-aperture radio telescope

Then there are the radio telescopes which most people do not know or even heard of until today, like me. These telescopes are a form of directional radio antenna which used in tracking and collecting data from satellites and space probes. They are different than the optical telescopes in that they operate in the radio frequency portion of the electromagnetic spectrum where they can detect and collect data on radio sources. They are often located far away from major centers or even town to avoid electromagnetic interference from radio, TV, etc. They are typically in a form of parabolic dish antennas used singly or in an array. The World’s largest single-aperture radio telescope is at the Arechibo Observatory in Puerto Rico.

Carrying the MSSTA on May 1991

Next are the X-ray telescopes. These telescopes are designed to observe remote objects in the X-ray spectrum. In order to get above the Earth’s atmosphere, which is opaque to X-rays, these telescopes must be mounted on high altitude rockets or artificial satellites. Here is a picture of the X-Ray telescope on the Swift MIDEX mission in May of 1991. The purpose of the telescope is to measure the fluxes, spectra and light curves of Gamma-ray busters and afterglows over a wide dynamic range covering more than 7 orders of magnitude in flux. It is about 4.67 meters in length with a focal length of 3.5 meters and a diameter of 0.51 meter.

Lastly, here is a diagram of the electromagnetic spectrum with the Earth’s atmosphere transmittance or opacity and the types of telescopes used to image parts of the spectrum.

I also hope that by showing and explaining various types of telescopes, you will become more interested in astronomy and help convinced Congress to bring back the funding for NASA and JPL so I can find a job when I finally graduate next year. J