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Frank Reed wrote:

> A big part of this error results from the fact that the ecliptic only
> looks like a sine curve. It's not a bad approximation, but the real
> curve has "broader shoulders" than a sine curve. It's easy to see this
> by imagining what the ecliptic would look like if the Earth's axis were
> tilted, say, 80 degrees instead of 23.45.



Frank,

It may be easy for you to visualize that but I'm afraid I can't see it.
I can visualize how things would be if the Earth's axis lay in the plane
of the ecliptic (i.e. a 90 degree tilt), since that reduces to 2D
geometry. But in that most extreme case, and assuming a perfectly
circular orbit, I think declination would change linearly from solstice
to equinox and vice versa -- meaning that the curve would have "narrower
shoulders" than a sine curve.

Can you explain how you see the "broader shoulders"? Or does the
explanation lie in the departure from circularity of Earth's orbit?


Trevor Kenchington


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Trevor J. Kenchington PhD                         Gadus@iStar.ca
Gadus Associates,                                 Office(902) 889-9250
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