Why only five planets discovered by the1700?

By the 1700s, only five planets were known—Mercury, Venus, Mars, Jupiter, and Saturn—primarily because of the limitations of observational technology. Telescopes were still relatively primitive, hindering the ability to detect fainter celestial bodies. Additionally, the understanding of the solar system was still developing, and many celestial objects were not recognized as planets until later advancements in astronomy. It wasn't until the discovery of Uranus in 1781 that the number of known planets increased significantly.