Comment on New forum by dizzib.

Stars are not what they seem. Check out this incredible amateur footage…

https://www.youtube.com/watch?v=nkDp4cJcGyc

#### Recent Comments by dizzib

Horizon

Fair enough WH, it seems we have different understandings :). Here’s mine: https://dizzib.github.io/earth/cet/asset/verge-1.png

Anyway thanks for that link, very interesting.

Horizon

Hi David, fisheye lens mapping functions do not depend on distance: https://en.wikipedia.org/wiki/Fisheye_lens

Horizon

Hi RSKJ,

Good questions. Observation says the horizon curves at altitude therefore it must be below eye level (as I explained a couple of posts ago). We can extrapolate and infer the higher we go the more it wil curve and sink down. We also know the higher we go the more of the earth’s surface we can see.

So at some extremely high altitude (way above the glass sky!), we can deduce the horizon will curve around to form a circle, and it will be so far below eye level that we’ll need to look down to observe it.

I’d imagine at the limit we’d be able to see half of the earth’s surface but the circle would be quite small!

Horizon

No, the vertical in-frame position of the horizon depends entirely on when I choose take the snapshot of the pitching horizon — a few frames earlier or later will have it appear higher or lower, therefore no conclusion can be drawn from its vertical in-frame position.

What’s important is both horizons lay on top of one another so we can make a valid comparison of their shapes.

The only thing we can observe from HAB footage is that the horizon becomes more curved at altitude, that is all.

btw at what altitude did you see your flat horizon? I’d wager much lower than this near-space HAB footage ðŸ™‚

Horizon

A curved horizon must necessarily be below eye level due to the properties of 3D space: imagine being in the centre of a large horizontally level hula-hoop — as you look left or right it appears as a straight line because it’s at eye-level. Now move up a bit so the hoop is below eye-level and you’ll start to see the curvature!

Anyway, I’m quite satisfied the horizon curves at altitude and is exactly what I expect to see in a concave earth with bendy light.