<HTML>You know, GH & RB strike me as putting great importance in moments when stars appear on the horizon, and moments when the stars appear just before sunrise.
Looking at their starmaps however, and reading their work, they forget two <B>vitally</b> important things, which any amateur or professional astronomer would consider:
1. Atmospheric Extinction.
Due to the light passing through increasing amounts of atmosphere, stars closer to the horizon are much fainter and thus more difficult to see.
Although the exact dimming depends on the quality of the atmosphere, the time of year, and the presence of any light pollution (a problem the AEs didn't have), comet-hunters and other astronomers do have ready-reckoner tables available.
Here is one such table. The first column (z) is the distance from the zenith (straight overhead). 90 degrees, the last entry, is right on the horizon. The second column (m) is the dimming in magnitudes at that altitude.
z m
== ===
1 0.28
10 0.29
20 0.30
30 0.32
40 0.37
50 0.44
60 0.56
70 0.82
75 1.08
80 1.59
81 1.75
82 1.94
83 2.19
84 2.50
85 2.91
86 3.45
87 4.23
88 5.41
89 7.38
90 11.24
Source: [
cfa-www.harvard.edu]
Now, as magnitude 6.0-7.0 is the faintest that people can normally see with the naked eye. The brighter star is Sirius at mag. -1.45, followed by Canopus at -0.92. Both these stars are <B>not</b> visible to the naked eye until they are at least a couple of degrees up, and they do not become prominent until they are 4 degrees up (when they are mag. 2 and mag. 2.5 respectively).
Of course, that's not all. We have to take into account twilight, which is my second point.
2. Twilight Extinction.
This is actually quite difficult to work out, and to the bext of my knowledge there are no easily-available tables. I can see why - important facts include the angular distance to the sun, the distance of the Sun beneath the horizon, the sky conditions. However, one figure that I have seen (in the September 86 issue of Sky and Telescope IIRC), is 3 magnitudes of dimming when the Sun is 15 degrees beneath the horizon. Certainly at the moment of sunrise, the dimming is on the order of 8 or more magnitudes. Bear this in mind when GH & RB talk about stars rising just before the Sun.
So what does this mean for Leo rising just before the sun as demonstrated in Chapter 17 of Keeper of Genesis/Mesage of the Sphinx?
Well, the faintest stars in the figure of Leo are about magnitude 3.5, and the brightest, Regulus is 1.4. The others range from 2 to 3.
Now, when the Sun is 12 degrees beneath the horizon, lets be generous and say that the extinction due to morning twilight is 3 magnitudes. As the stars are all within 10 degrees of the horizon, atmospheric extinction is <i>at least</i> 2 magnitudes.
So where does that leave Leo rising on the horizon just ahead of the Sun in 10500 BC?
Well, we have combined visual extinction of at 5 or more magnitudes. But the brightest star in Leo is only mag. 1.4! Translated into real visual magnitudes, this means that in the configuration that they have given, the brightest star in Leo is only mag. 6.4 - in other words, not visible to the naked eye (or just barely to those people with good eyesight).
So the question now must be asked? Why would the inhabitants of 10500 BC align everything up in the manner that Bauval has suggested to constellations that are invisible without a telescope?
Best Regards,
Dave</HTML>
