Roger Bailey wrote:
> Dear reto ambrosini,
>
> Thank you for the reality check on the sunrise formula. It is not an
> approximation but an accurate mathematical formula for an ideal world.
> Thank goodness we live in the real world where there is air to breath and a
> large sun to keep us warm. For this real world we have to make adjustments.
> The fine print in my original note said "ignoring refraction and
> semi-diameter, etc". I am glad that you raised the question and others have
> answered it so well.
>
> The basic formula for altitude, sin A = sin L * sin D - cos L * cos D * cos
> t, is also beautiful in its symmetry but it is too long to fit on a tee
> shirt, even here in North America where the most popular size is XL.
>
> Let me keep the thread going with another challenge. You have all observed
> how much larger the full moon is when it is near the horizon, rising or
> setting, compared to when it is high in the sky. Does this effect also
> apply to the sun at sunrise and sunset? Is a larger semi-diameter
> correction needed to account for this?
>
> Roger Bailey
> Walking Shadow Designs
> Canmore, Alberta, Canada
> >
> >
Hello Roger,
I sincerely hope your statement regarding how the moon appears larger when
near the horizon was submitted in jest. I'm sure you are aware that the moon's
(or sun's) diameter remains constant regardless of whether it is located near
the horizon, or high in the sky. The effect is merely an optical illusion
brought on by the ability of one's eyes to make comparisons with known objects
near the horizon, e.g., trees, buildings, etc.
