Spiros Wrote:
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> The computations were performed by beings of an
> advanced civilization.

What computataions ,and where are these computations ?


In New York the horizon is pretty
> much flat, but this is not the case in most of the
> places in Greece. Mountains all over the place.
> The actual horizon is not the best option in this
> case.

As mentioned previously the horizon towards the rising sun at Pella on the date of Alexanders bithday is much the same as at Manhattan and because the latitude is also very close the azimuth towards the setting sun at both sites will be very similar .
There are hills that rise to 1500 m to the north west of Pella but the sun never sets that far north for them to be taken into consideration and they don't impact on the horizon calculation for Alexander's birthday . If they did the coincidence of the two sites sharing a similar latitude and horizon altitude , like so many other places on the globe , would be truly scuppered .


> So my proposition is that the ideal horizon was
> taken into account. The actual horizon might also
> have been taken into account.

There is no such thing as an ideal horizon ,that is a euphemism for those who are unaware of taking the real horizon into consideration when calculating declinations and alignments .It happens all the time , people look up sun rise and sun set bearings on the web ,not realising that these sites can't , and don't take the horizon into account .They are merely guides ,that are relatively accurate as most large cities tend to have relatively flat horizons .