How far an Pegasus II see from the apex of the flight?

That question is complicated by the atmospheric conditions at the time.  Light refraction comes into play because the denser layers of the atmosphere, closer to the surface, bend light and extend the visible distance.  There are a host of factors that come into play at the point in time the observation is made, either extending or reducing the theoretical limit due to refraction.  Most of the time it will reduce it.  A calculation without using refraction produces a smaller visible range, a range likely to be exceeded by an unknown amount.

The apex of Pegasus II’s flight ~111K feet, should have enabled us to view some or part of 40% of the number of states in the United States and some of Canada.  Not a bad stat.