Once the radiation from an astronomical object has passed through Berth’s atmosphere, it must be gathered into a form that enables us to detect it fairly easily. Only after this detection has taken place and the signal from the object recorded can any analysis of the data take place.

Astronomical objects are so far away that they have a low apparent luminosity. Radiation which reaches Earth from any one point in the cosmos is travelling in a parallel beam for all practical purposes. It is clear, therefore, that a collector of electromagnetic radiation, or TELESCOPE as it is usually called, has two main functions: firstly, it must collect radiation from as much of the parallel beam as it can and, secondly, it must concentrate or FOCUS this radiation onto the detector so as to give a sharp image of the object.

It is important to remember in the following discussions that although radio, infrared, optical, ultraviolet, X-ray and gamma-ray telescopes often look very different, the principles of optics which govern their design are the same. No particular wavelength is implied in this discussion based on general principles unless it is explicitly stated.

Comments are closed.