How Much Brighter Do Stars Appear From Space?
Question:
I’m wondering: how much brighter are the stars (in magnitude), from space (e.g., ISS, the lunar surface, etc.)? Is there a way to figure magnitude, like, in the Bortle Scale?
Answer:
As the light from a star passes through the Earth’s atmosphere some of that starlight gets absorbed. The amount of starlight absorbed depends upon the amount of atmosphere between the observer and the star, which varies with time of year, the observer’s altitude, and the apparent height of the star above the horizon. When one adds-up the various contributions to that absorption one finds that on average a star’s apparent magnitude is increased (it becomes dimmer) by about 0.3 magnitudes for an observer at sea level observing a star at the zenith. For that same star observed near the horizon, the star’s apparent magnitude is increased by about 11 magnitudes.
