Observatories are put on high, dry, dark peaks. Which limitation does the dryness attack?

1. Air limits a telescope in four separate ways, and each site quality answers one of them. 2. Water vapor in the air absorbs starlight, most strongly in the infrared. 3. A dry site holds little water vapor, so more infrared light survives the trip down. 4. Height mainly buys thinner, steadier air above the telescope. 5. Darkness answers light pollution, the glare scattered by city lights. 6. Steadiness answers bad seeing, the blurring caused by turbulent cells of air. 7. Clear weather answers cloud, and the best sites are clear as much as 75 percent of the time. 8. So of the choices offered, only the infrared absorption is the problem that dryness fixes. _Source: OpenStax Astronomy (CC BY 4.0), section 6.2 Telescopes Today_