What is the biggest hindrance to Earth-based astronomy?

Light pollution is indeed the most significant hindrance to Earth-based astronomy. It refers to the excessive or misdirected artificial light that brightens the night sky, making it difficult for astronomers to observe celestial objects. This can obscure fainter stars and other astronomical phenomena that are crucial for research and study.

When light pollution is present, it overwhelms the subtle light emitted by distant stars and galaxies, leading to challenges in both visual observations and the accuracy of data collected. Astronomers require dark skies to capture detailed images and gather meaningful data; thus, light pollution poses a major obstacle.

Cloud cover, air pollution, and poorly built telescopes, while they can hinder observations, do not have the same pervasive effect across all observational conditions as light pollution does. Cloud cover can obstruct specific instances of observation, air pollution can affect visibility and clarity, and poorly built telescopes can impact performance, but they do not systematically diminish the ability to observe the night sky on a broad scale like light pollution does.