Before the invention of the telescope, astronomers relied on a variety of tools and techniques to observe and study the celestial objects and phenomena. The simplest and the most ancient method was unaided observation with the naked eye. However, early astronomers extended their observational capabilities through a variety of instruments like the astrolabe, quadrant, sextant, and armillary sphere. One of the last major astronomers who harnessed these tools to achieve remarkably precise astronomical observations was Danish astronomer Tycho Brahe.
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Tycho Brahe's Uraniborg observatory.
Source: amusingplanet.com