Many people think that Galileo Galilei invented the telescope. That’s not true. A patent application for a telescope design in the Netherlands was rejected just a year before Galileo build his own device. Some of the most important elements of telescope optics were described by the Iraqi scientist Ibn al-Haytham in the 11th Century. Galileo was the first to turn his telescope upwards. Believe it or not, nobody had thought to take a telescope and just look to the heavens and write about it.
There are many different types of telescopes: refractors (with lenses), reflectors (with mirrors) and catadioptric (a combination of lenses and mirrors). Within each group you can find variations on each design, such as a Newtonian-reflector, a Schmidt-Newtonian, a Dobsonian, a Schmidt-Cassegrain or a Maksutov-Cassegrain (both of these last two are catadioptric telescopes). Which of these telescopes are best? None of them. It all depends on your preference and considerations. A small refractor is one of the more affordable telescopes, as is a large Dobsonian. Catadioptric telescopes are easy to set up and compact, but by design have a large secondary obstruction affecting contrast.
There are also different types of mounts for telescopes: an alt-azimuth and an equatorial mount. (EQ) An alt-azimuth mount is common: you might see them on Schmidt-Cassegrains. These mounts are able to move the telescope up and down and from side to side. An EQ mount moves the telescope in right ascension (RA) and declination (Dec). Right ascension and declination are used to navigate the night sky. An easy way to think of these is as longitude and latitude. Right Ascension is the “up-down” like longitude, and declination is the left-right, like latitude. But where is the “North Pole"? We use North Star, Polaris, as a rough marking of due north. Equatorial mounts are able to navigate the night sky in this manner, so are excellent for long observing sessions or astrophotography.
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