Optical Telescopes are instruments designed to make distant objects appear nearer to the human eye.
There are other types of telescopes that can collect different frequencies of electromagnetic radiation including x-rays, ultraviolet, and infrared.
Optical Telescopes were invented around 1600,the first examples being simple,in effect a long tube with a combination of convex and concave lenses(one being the objective lens and the other lens the eyepiece).
Shortly after their invention,the design was improved to incorporate two convex lenses,which produce an upside down image.
Apart from improvements in lens manufacture this design is still in use today.
They are known as REFRACTOR TELESCOPES.
There was however a problem with these first telescopes(which has now been resolved) called a rainbow halo which led to Isaac Newton developing a REFLECTOR TELESCOPE in about 1680 which used a mirror to collect light and reflect this to a focus.
Fast forward to 1930 when a German astronomer invented a COMPOUND or CATADIOPTIC TELESCOPE which as it’s name suggests is a combination of both lenses and mirrors.
This was superceded in the 1960s by the Schmidt-Cassegrain design,which has become today’s most popular type of telescope.
Optical Telescopes are mainly used for astronomy,they are also used in bird watching,various sporting activities and also have military uses.
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