The object in sight is also a key aspect when photographing distant horizons.
This relevance is specially related with the color of the distant object, as we require a certain contrast between it and the background, that will usually be moderately illuminated and light blue.
Common mountains are dark brown, loosing color strength with distance, becoming light brown, or even light blue.
Atlas mountains (870 m. / 205 km.), Morocco, as seen from Mulhacen (3.479 m.), Spain
In this image we can see how the moutains appear as light blue, while the sky in the background is some steps lighter and this difference creates the contrast required for the mountain to be seen in the distance.
When mountains are snow covered the situation is different and better for us.
Snow covered mountains are light white and the distance just decreases the luminosity, while not changing the color as much as with “brown” mountains.
This effect is a way to assure that snow covered mountains will be easier to be seen from the distance, as the contrast with the background will be greater.
Posets (3.369 m. / 251 km.) from Cantavieja (Teruel – Spain)
As we can see in the image above, background sky is light blue again while the snow covered mountain is nearly white, a color with higher contrast with the background.
Light reflecting snow is also a help for our purposes, as this light is also increasing contrast.
Beyond Horizons 