RickandRhonda wrote:Given perfect conditions, and taking earth curvature into consideration, your horizon would be approximately 257 miles away on Rainier. Theoretically, your horizon on Denali would be 304 miles away. This assumes perfect conditions, and is the mathematical maximum.

Source: http://newton.ex.ac.uk/research/qsystems/people/sque/physics/horizon/

Very interesting project. I'll be interested to see just how far from Rainier I can get and still see it.

Please note: the formula I mention only calculates the theoretical distance between the height of an object and the horizon. It does not calculate the theoretical distance between two peaks. (And is thus, slightly off topic.)

Using the link you provided, which appears to be correct, using the formula d^2 = 2rh + h^2, the theoretical horizons for Rainier and Denali are not what you wrote. Note the form's elevation field requires meters. So Rainier at 4392 meters has a sea-level horizon distance of 236.7 km (147.1 mi). The calculation for Denali at 6194 m gives 281.2 km (174.7 mi).

I could not figure out what numbers you entered to get 257 and 304 miles.