Yahoo Answers: Answers and Comments for How far away can you see mountains from? [Geography]
Copyright © Yahoo! Inc. All rights reserved.
https://answers.yahoo.com/question/index?qid=20100312202402AAMs7Cv
From Amoonalu
enUS
Fri, 12 Mar 2010 20:24:02 +0000
3
Yahoo Answers: Answers and Comments for How far away can you see mountains from? [Geography]
292
38
https://answers.yahoo.com/question/index?qid=20100312202402AAMs7Cv
https://s.yimg.com/zz/combo?images/emaillogous.png

From Anonymous: Follow me on this, because I'll explain.
...
https://answers.yahoo.com/question/index?qid=20100312202402AAMs7Cv
https://answers.yahoo.com/question/index?qid=20100312202402AAMs7Cv
Fri, 12 Mar 2010 21:42:10 +0000
Follow me on this, because I'll explain.
Let's say that you were looking at Mt. Everest, unobstructed from sea level with no atmospheric distortion of any kind, no haze, no nothing, just idealized optic conditions.
The equation to determine just how far someone could stand and see the tiptop (baring the atmospheric refraction in reality...), with the unit given in miles:
D = SQRT { (3 * H) / 2 }
So let's just call Everest 30,000 feet. Hence...
D = SQRT { [ 3 * (30,000) ] / 2 }
D = SQRT { [ 90,000 ] / 2 }
D = SQRT { 45,000 }
D = 212 miles
So you could see Everest from 212 miles away on a perfect day.
What would you need to see mountains 800 miles away? Follow 
You'd need:
H = [2D^2] / 3
H = [ 2 * (800)^2 ] / 3
H = [ 2 * (640,000) ] / 3
H = [ 1,280,000 ] / 3
H = 427,000 feet...
So your mountains would have to reach 81 miles, which is 20 miles beyond where we define the boundary between atmosphere and "outer space."
Probably should pick a smaller distance for your heroine.

From Anonymous: if you're at sea level, you can start seei...
https://answers.yahoo.com/question/index?qid=20100312202402AAMs7Cv
https://answers.yahoo.com/question/index?qid=20100312202402AAMs7Cv
Fri, 12 Mar 2010 20:46:19 +0000
if you're at sea level, you can start seeing the top of a 4km mountain at a max distance of ~225 km.
To see a mountain from 800 miles away, the mountain would have to be about 155 miles high.
Ain't none on this planet.

From Anonymous: Well, 800 miles is a bit far unless the mounta...
https://answers.yahoo.com/question/index?qid=20100312202402AAMs7Cv
https://answers.yahoo.com/question/index?qid=20100312202402AAMs7Cv
Fri, 12 Mar 2010 20:34:15 +0000
Well, 800 miles is a bit far unless the mountains were really high up. I think your distance is too far for you to be able to see a clear horizon on the mountains. You may want to change the distance.