Chris Tedder Wrote:
-------------------------------------------------------
> Have you considered the effects of atmospheric
> extinction?
>
>
> Pleiades is a distinctive, but fairly dim small
> star cluster. When near the horizon Pleiades is
> invisible to the unaided eye that can see stars
> down to about mag. 6 - with no moon, very dark
> sky, and excellent eyesight, to about mag. 8.
>
> Alcyone is a mag. 2.85 star and when Taygeta was
> on the horizon it was about alt 10’ extincted down
> to about mag. 9-10. Atlas is a mag. 3.6 star
> extincted down to about mag. 10 at 37’ alt. with
> Taygeta on the horizon.
>
> Pleiades needed to be at least 2 degs above the
> horizon for it to be barely visible, but even
> then, only by someone with exceptional eyesight.
> This means the angle between Atlas and Alcyone was
> impossible to measure accurately with the unaided
> eye – only a very rough estimate was perhaps
> possible.
>
> Chris
>


Thanks for that information. That means that the pyramid must have been built after 2944 BC. So 3 degrees 17 minutes would be sufficiently high for clear visibility then? That's what the altitude of the lowest star in the Pleiades was in 2600 BC when Alcyone was due West. So that places the construction right within the standard chronology. I guess the builders depicted the Pleiades with Taygeta at the pyramid base simply because that would place the chambers in practical positions rather than way up near the top.

Regarding just how visible the Pleiades are from Giza, this image should clear things up. Looks rather clear to me. I think I could actually ascertain the angles between the stars by naked eye, and that photo is from modern times with all the light pollution. The Pleiades are about the same size as the Sphinx's head in this photo, and I can see the Sphinx's head quite well.



Now what if you were an Egyptian tomb raider and you made it inside the pyramid? You would find two chambers in the main body of the pyramid which appear to have been plundered by someone before you. You would think to yourself "the tomb chamber must be below the pyramid". You would go down to the subterranean chamber and say "gee, they didn't even finish this thing, nothing here. Darn, somebody beat me to raiding the Great Pyramid. Well, I think I'll just go home now". Khufu's tomb chamber is completely safe with no passages leading to it that anyone can find. Quite an ingenious plan really.




Edited 3 time(s). Last edit at 01/10/2013 08:16AM by Rigel_7.