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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: The Star of Bethlehem and Navigation
From: Frank Reed
Date: 2009 Jan 3, 16:44 -0800
From: Frank Reed
Date: 2009 Jan 3, 16:44 -0800
Marcel, you wrote: "I'm wondering whether the special event in the sky could have been in relation with this "conjunction" and the moon, like e.g. the moon occulting two or three planets at the same time." I've never heard of such an event in that time period. Given that people have been trying to come up with plausible conjunctions and occultations to somehow explain the Star of B since at least the time of Kepler, I suspect they've probably found the genuinely interesting cases. But try it for yourself. It's certainly possible that something's been missed! I recommend Aldo Vitagliano's "Solex" software for this sort of thing: http://chemistry.unina.it/~alvitagl/solex/. It has a primitive user interface, but it's very fast, the accuracy is extremely high, and it can show almost any set of circumstances. And: "I imagine that such an event is fairly rare and could have been a reason for those dealing with Astronomy/Astrology for travelling to a distant place where they could see it." Any such event would have been visible along a long path (a "line of position" in fact). Even if they had the predictive ability to determine that an event would not be visible from their own longitude and latitude (and this is unlikely), they could not have determined a single location just by the requirements of visibility. And: "After what I learned here, this should be possible to verify for the location. If I understood it correct, the inaccuracy of +/- 2 degrees seems only to refer to the local hour angle "Tau" and not to the declination, i.e. that the calculated declinations would actually be fairly exact." Rather than saying calculated declinations, it would be fair to say that the "geocentric positions (right ascensions and declinations)" would be fairly exact. Fairly exact for the date in question means that the geocentric RAs and Decs would be generally accurate to the nearest arcsecond for the planets and accurate to +/-5 arcseconds for the Moon. For some true stars, the positions may also be as inaccurate as the position of the Moon. And since the uncertainty in local time affects only longitude (on the Earth), you could also say that any maximum or minimum latitude calculations would be fairly exact. By the way, the introductory web page shows an example of an ancient astronomical observation (the most ancient?) that puts a strong constraint on delta-T: the solar eclipse of March 5, 1223 BC seen at Ugarit in Syria. If we have records stating that an eclipse was seen from a specific place, all we need to do is change delta-T by trial and error until the eclipse path crosses the observer's location. The catch in this case is that the tablets recording the eclipse aren't dated. So you need some other information to narrow the date to the nearest century or two. -FER --~--~---------~--~----~------------~-------~--~----~ Navigation List archive: www.fer3.com/arc To post, email NavList@fer3.com To , email NavList-@fer3.com -~----------~----~----~----~------~----~------~--~---