If one is located behind a mountain, what time is Shkiya or Tzeis?
- Is it when the sun sets below the "calculated" horizon (when the sun should set had the mountain not been there)?
- Is it when the sun sets behind the mountain?
What if one is on top of a mountain? Is Shkiya/Tzeis affected the same way?
What if one is on top of a building, is Shkiya when the sun sets for him or when it sets for people on ground level?
PLEASE BRING SOURCES