Advantages and Disadvantages of Different Types of Telescopes

Telescopes	Advantages	Disadvantages
Refracting	Closed tube so very little maintenance and images are more steadier and sharper Hard to disrupt alignment	Production is expensive of large lenses and they can sag as there is no support in telescope Works only at night Prone to spherical and chromatic aberration Thick lenses absorb more light
Reflecting	Large mirrors are cheaper to make than large lens Mirror only needs to be polished on one side Only parabolic removes spherical aberration Not prone to chromatic aberration Primary mirror is supported so they can be big	Works only at night Open tube so needs maintenance Easy to disrupt alignment Secondary mirror can produce diffraction effects on image
Radio	Use a wire mesh as the long wavelength radio waves do not notice the gaps, construction is easier and cheaper It does not need to be as precise as a polished mirror Radio telescopes can work in all weather conditions Radio telescopes can work during the day and night Instead of one big dish, a number of dishes can be linked together and when the distance between them is increased, the image becomes sharper	The radio telescope dish has to have a precision of λ/20 to avoid spherical aberration Radio telescopes have to scan across a radio source to build up an image which is time consuming
IR	Detects anything that gives off heat	Detector needs to be cooled to low temperatures as it gives off heat as well Can only view near IR so high, dry altitudes or orbit to view higher wavelengths
UV	Can detect objects not seen in other wavelengths	Can only view near UV so orbit to view lower wavelengths
X-ray	Can detect objects not seen in other wavelengths	Mirrors need to be at very low angles in order to work Can only view x-ray in orbit to view it’s wavelengths

©2011 Grant Dwyer