So now we’re in the earth getting this angle are we Danny? Burning in the firey hells of the molten iron core to acquire this lying angle.

Nathan Oakley, Flat Earth Debate 1894.

Ignorant (willfully or otherwise) of the geometry of celestial navigation, Nathan has to misrepresent it’s basis in fact and reach for a snappy soundbite instead.

The Reality

The practice of celestial navigation is underpinned by the geometry of the spherical earth and distant celestial objects. This geometry requires the centre of the earth to coincide with the centre of the celestial sphere (above), the imaginary sphere on which celestial objects are mapped.

The diagram below shows rays of light from a celestial object intersecting the earth. The elevation angle and it’s complement, the zenith angle, are indeed calculated as if observed from the centre of the earth. Measuring from the surface, a correction needs to be made to account for the observer’s actual position on the earth.

However, as the light rays in the case of stars are coming from extremely distant objects, they are as good as parallel and so no correction is required. Solar system objects are much closer and show measureable shifts in position (parallax) as you move across the face of the earth.

PARALLAX (or diurnal parallax), is the difference between the true altitude of the sun, moon, or stars, observed at the centre of the earth, and its apparent altitude, observed at any point of the earth’s surface.

Nathaniel Bowditch & Gilbert Stuart , 1802. The New American Practical Navigator (first edition).

In the case of the moon, it is close enough to show a 1 degree shift in parallax. Celestial navigation tables give this correction in the horizontal parallax (Hp) columns.

Nathan, like every other flerf, does not like to talk about flat earth. He has to lie about the globe instead. #gottalietoflerf