Final answer:
Sites for astronomical observatories require clear weather, dark skies, low water vapor, and minimal atmospheric turbulence, necessitating dry and high-altitude locations. High-quality photos taken on clear days after site visits can help develop visibility charts, sharing similarities with air traffic control using radar to navigate obscuring weather.
Step-by-step explanation:
The selection of sites for astronomical observatories is a meticulous process that involves considering various environmental factors that affect the quality of observations. For a visible-light observatory, the main criteria include clear weather conditions, which entail a location where the weather is predominantly cloud-free and clear as much as 75% of the time. Dark skies are also crucial, meaning the site should be located away from urban light pollution, preferably at a distance of at least 100 miles from large cities. Additionally, excellent atmospheric seeing conditions are necessary, which suggests low atmospheric turbulence; this can be found in high-altitude and dry locations, where there is less water vapor to interfere with the starlight, particularly in the infrared spectrum.
For an infrared observatory, a dry site is particularly critical because water vapor primarily absorbs infrared starlight. Meanwhile, a radio observatory has different needs, such as being distant from radio-frequency interference, which is often man-made.
It is recommended that after visiting potential sites, observers should promptly take high-quality digital photos on clear days, which can assist in the development of visibility charts and markers adding valuable information about the current state of the airfield/site. These details are essential, analogous to air traffic controllers using radar instruments to penetrate obscuring weather layers.