Atmospheric Absorption of Starlight

[sderamus]

I realize that Starlight atmospheric absorption depends on frequency, but I was wondering if there are any tables indicated total bolometric absorption at Zenith relative to absorption at Sea Level. Obviously atmospheric absorption is much less on the top of Everest than in my hometown (a few hundred feet above sea level). But I'd like to know the difference.

TIA

sderamus

 

[Wallace]

The absorption depends on so many factors that there isn't (to my knowledge) any simple tables.

By the way Zenith refers to an angle in the sky (essentially straight up) while sea level refers to altitude on the Earth, so they are very different things! Absorption will depend on both of these factors as well as other conditions such as the local humidity, particle concentration and even temperature.

 

[sir-pinski]

Hello sderamus,

Thank you for your question about atmospheric absorption of starlight. You are correct that atmospheric absorption depends on frequency, as different wavelengths of light interact with the atmosphere in different ways. However, there are also other factors that can affect the total bolometric absorption of starlight at different locations, such as air density and humidity.

There are some tables and charts available that show the average atmospheric absorption at different altitudes, including at sea level and at the top of Mount Everest. For example, the National Oceanic and Atmospheric Administration (NOAA) provides a chart that shows the average atmospheric transmission for different wavelengths of light at sea level, 10,000 feet, and 20,000 feet. According to this chart, the average transmission at sea level is around 80%, while at 20,000 feet it is closer to 90%.

Another factor to consider is that atmospheric absorption can also vary depending on the time of day and atmospheric conditions. For example, light from stars may be more absorbed during the day when the sun is out and the atmosphere is warmer, compared to at night when the atmosphere is cooler and more transparent.

In general, the difference in atmospheric absorption between sea level and the top of Mount Everest would likely be relatively small, as the majority of the Earth's atmosphere is within the first few kilometers above sea level. However, there may be some slight variations due to differences in altitude, air density, and other factors.

I hope this helps answer your question. Thank you for your interest in atmospheric absorption of starlight. Have a great day!