Guest guest Posted March 14, 2003 Report Share Posted March 14, 2003 Ken Bowser posted: > >Message: 3 > > Wed, 12 Mar 2003 15:02:22 -0000 > > " Ed Kohout " <crumpo@e...> > >Re: sidereal reference frames - Ed. > > > >Hi Juan! > > > >Thanks for the fine info, and the insights. You are truly the Dean > >of Astronomy in our ranks. It shows that I read too many astrology > >books and not enough technical stuff. > > > >But, I still say that the " sidereal zodiac, " no matter what the > >Babylonians used, is now calculated as some delta from the vernal > >point, and thus defined as such, and not by reference to any fixed > >star near the ecliptic; nor is it somehow anchored on some fixed > >point in space. > > > Dear Ed, > I think your comments about proper motion are misleading. It > depends very much on which stars you're talking about. You > couldn't throw Bernard's freight train, for example, into the mix. > Let's look at Antares, one of the prime fiducial stars in the sidereal > zodiac, important to both the Babylonians and latter day > siderealists. It's apparent place on January 1, 1901 according to > the American Ephemeris and Nautical almanac was, > RA 16h 23m 20.1s > dec. -26 deg. 12' 38.8 " > when these values are converted to celestial latitude and longitude, > one gets a tropical longitude of 8 Sag. 22' 46.75 " and latitude > -4 deg. 33' 19.86 " > The sidereal longitude was 15 Scorpio 01' 02.85 " . > > One hundred years later for January 1, 2001 the apparent place of > Antares according to the Astronomisches Rechen-Institut, an > internationally recognized authority was, > > RA 16h 29m 25.73s > dec. -26 deg. 25' 54.29s > Converting these values to celestial longitude and latitude one gets > a tropical longitude fugure of 9 Sag 45' 59.71 " and latitude of > -4 deg. 34' 11.5 " . The sidereal longitude for this period was > 15 Scorpio 01' 00.7 " > The difference in tropical longitude in 100 years for this star is > 1 degree 23' 12.95 " or 4,992.95 seconds in 100 years. > > The difference in sidereal longitude in 100 years is 2.15 seconds, > so yes, you're right, if you insist on splitting hairs, proper motion is > a factor but it will take several millennia for sufficient proper motion > to accrue such that the difference between now and then could > subtend an arc capable of being discerned by the human eye. So > as a practical matter the sidereal zodiac is a fixed frame of > reference. This is an excellent point, and I am fully aware that proper motion is indeed indetectable to the unaided eye, let alone someone who can live for one millennium. > I'm therefore confounded as to why you would claim > that sidereal reckoning is secondary to tropical because in the > ancient world the equinox was described in terms of the sidereal > zodiac, not the other way around. Two probems with that. One is that the " equinox " never existed as a concept for the " ancients. " They saw the zodiac as a band, or strip, of sky that was bounded by the trek of the Moon, and had no concept of the earth/sun plane. The other is that the " ancients " are not alive today, and we don't engage in astrology like they did. We live in highly technical milieu now, and they rode around on camels. We have the abilty to plot an ecliptic, and they did not. The modern " zodiac " is reconed as a sphere, with the earth/sun plane as the fiducial of latitude. Earth/sun is independent of fixed stars, as is the earth/sun node that we call the vernal point. This vernal point, as a stand-alone, is a viable measure, as well as mathematically finite and easily calculable. We even know where its pivoting points are. > Fagan and Bradley were not looking to put Aldebaran at the > fiducial point. They found it there courtesy of Joseph Epping S.J., > Johann Strassmaier S.J. and F. X. Kugler S.J. who spent much of > their adult lives deciphering Babylonian and Assyrian astronomical > texts, which were brought together and expanded by Otto > Neugebauer in his Astronomical Cuneiform Texts. Thank you for that info; i was unaware. > I'm further confounded as to why you would maintain that 1st > Nisan of April 3, 786 B.C. was invisible. I'm getting my data from my astronomy program, Sky Map, which is highly accurate with Delta T. The data is posted below (I used Bagdhad as the location). The most important datum is the one at the end. ====================== Information about Moon for 03 Apr 786 BC 7:03:19 PM (Julian day number 1434429.16897) Local Information Apparent topocentric coordinates for the epoch of date: Right ascension: 0h 51m 15.58s Declination: +8° 8' 4.1 " Constellation: Aries Altitude: 0° 17' 36 " Azimuth: 279° 54' 2 " Hour angle: 6h 22m 40s Rise: 6h 8m 39s Transit: 12h 33m 15s Set: 19h 6m 18s Star atlas chart numbers: Herald-Bobroff Astroatlas, Chart C-36 Millennium Star Atlas, Charts 163-164 (Vol I) Sky Atlas 2000.0, Chart 4 Uranometria 2000 Chart 131, Vol 1 Geocentric Information Apparent geocentric coordinates for the epoch of date: Right ascension: 0h 54m 18.504s Declination: +8° 38' 2.51 " True distance: 403628.7 Km Horizontal parallax: 3259.53 " Physical Information Magnitude: -5.1 Phase: 0.009 Phase angle: 168.8° Elongation: 11.1° ============================== > The New Moon in right > ascension occurred at 8:50 PM LMT on the evening of April 2nd > and the New Moon in longitude more than an hour before that. So > if sunset was at about 6:10 PM on the evening of April 3rd at > Babylon and the Sun would have been sufficiently depressed below > the horizon about thrity to thirty five minutes later for the Moon to > be seen, that means the Moon was about 22 hours old and had > sufficient altitude to be seen. > The youngest Moons are 14 hours > old and although a Moon that new is rare, a 22 hour Moon is not > rare. Other factors go into whether the moon is visible, including location on the planet, declination, atmospheric conditions, etc etc etc. Such simple predictability as you suggest is not likely. A good site to read is this: http://aa.usno.navy.mil/faq/docs/islamic.html >>>The visibility of the lunar crescent as a function of the Moon's " age " - the time counted from New Moon - is obviously of great importance to Muslims. The date and time of each New Moon can be computed exactly (see, for example, Phases of the Moon in Data Services) but the time that the Moon first becomes visible after the New Moon depends on many factors and cannot be predicted with certainty. In the first two days after New Moon, the young crescent Moon appears very low in the western sky after sunset, and must be viewed through bright twilight. It sets shortly after sunset. The sighting of the lunar crescent within one day of New Moon is usually difficult. The crescent at this time is quite thin, has a low surface brightness, and can easily be lost in the twilight. Generally, the lunar crescent will become visible to suitably-located, experienced observers with good sky conditions about one day after New Moon. However, the time that the crescent actually becomes visible varies quite a bit from one month to another. The record for an early sighting of a lunar crescent, with a telescope, is 12.1 hours after New Moon; for naked-eye sightings, the record is 15.5 hours from New Moon. These are exceptional observations and crescent sightings this early in the lunar month should not be expected as the norm. For Islamic calendar purposes, the sighting must be made with the unaided eye.... ....This large range of possible elongations in the one-day-old Moon is critical, because at this time the width of the crescent is increasing with the square of the elongation, and the surface brightness of the crescent is also rapidly increasing. Some of the earliest reliable sightings of the crescent occur near elongations of around 10 degrees. Obviously, simply specifying the age of the Moon cannot tell the whole story. Of course, the elongation of the Moon does not tell the full story, either. But, of the two parameters, the elongation is a much more reliable parameter to use as a starting point in assessing the lunar crescent visibility at any given date and time. <<< This particular crescent set when the Sun was at 10*27' below the horizon, which is However, all of that is irrelevant, as this chart for Nisan was almost certainly calculated using the planetary motion tables and the calendar, and not by sight on that day. Thus, whether or not this first crescent was visible for two minutes, twenty seconds, or not at all, is irrelevant, and I probably should have never brought it up! lol > How then can you blithely dismiss this New Moon as > invisible? The only issue which could put the matter into doubt is > the modest difference in azimuth between this Sun and Moon but > the Moon's anomaly can easily take care of that issue. Again, see the data above, or find some other more technical data to show your point. If this first crescent was visible, it was at the very threshold of visibility, and thus probably it is best to say it was not visible. > Even though the earliest horoscope extant dates to 410 B.C., > astronomical/astrological work does not appear ex nihilo. Abraham > Sachs, who along with Neugebauer was in perhaps the best > position to know, stated that while there is no evidence extant for > it, he assumed the tradition to be some centuries earlier than 410. > Just how far is difficult to say because the solid evidence for period > relations and the kinematic model that allows predictions of future > planet positions is a late development. But it is significant that one > can't solve the problem of period relations with a tropical system of > reference because era to era comparisons break down except with > sidereal reckoning. It is only by comparing sidereal and synodic > periods from one era to another that period relations can be derived. > You can't do that with tropical reckoning. A good point, and one that Juan brought up earlier, but asunder of the fact that the sidereal zodiac you use is based upon an ecliptic that is defined as the trek of the Sun. The fiducial is the node of our equator and that ecliptic, and while it is undoubtedly true that some other referents must be used to derive ephochal constants, we must also realize what it is we are measuring in the first place. Comparing ancient Babylonian astrology to be equivalent to modern sidereal astrology is somewhat misleading. > Besides, nobody could > find the equinox in the ancient world anyway. All of Ptolemy's > measurements of it were wrong although he got some of them > tolerably close; and except for Callipus' lucky hit in 330 B.C. the > equinox was a very approximate thing, not remotely as definitive a > fiducial as a star all through early and late antiquity. I agree, but if you really want to be like the ancients, why not have a sidereal equator, which is closer in definition to what they used. Sidereal motion, back then, was also a matter of pole stars, and thus the grid of right ascension. As for the equinox, all one needed to do was measure when the sun rose or set due east or west, and then count the hours until one's favorite fixed star culminated. Great observatories were built just for that purpose in Egypt. > You state that the Babylonians could calculate the position of > the Moon acurately in 786 B.C. and yet you throw cold water on > the zodiac then. Hardly a good representation of what I said. Moon phases were the benchmarks of the calendar, which was how agrarian society was possible. It had nothing to do with " zodiacs, " which came about aeons later. > I don't maintain that it is so, although the > exaltation solution is suggestive, but it should be borne in mind > that the zodiac is a tool that facilitates positional computations. > That's how they did it. I'm not getting your point here. > That's what the normal stars were for. The > 12 fold equal division zodiac comes directly out of the normal star > schema. This is untrue. The 12-fold equal division zodiac comes from Greek intervention and the realization that a tropical year was about equal to 12 lunations. This is why we have 12 months (from the root " moon " ) and not 12 constels some other nomenclature. There is no " normal star schema. " > The question is when did they change from the 17 > unequal constellations of circa 1100 B.C. (according to Francesca > Rochberg-Halton in her 'New Evidence for the History of the Zodiac' > [Journal of New Eastern Studies, 1984]) to the 12 fold equal > division format. That question is rather irrelevant to the discussion, but it is thought to have occurred as early as the 6th C BC. > Fagan's work rested firmly on the scholarship of almost a > hundred years when he realized in 1944 that the Babylonians had > used a sidereal zodiac. If you are saying that Fagan realized that the Babylonians used a system of measurement that did not take into account precession nor vernal points, you are surely correct. If you are saying that Fagan found that the Babylonians used an " ecliptic, " you are surely mistaken. The chart you mention above, that earliest birth chart know to us, has no references to any zodiac, but instead fixed stars. Fixed stars and sidereal zodiacs are not the same thing. And, finally, no one has yet to answer my question about the fact that any sidereal zodiac (Fagan, Lahiri, et al) is defined as some delta (ayanamsa) to the vernal point, which is by definition tropical. It's not the other way around, even if fixed stars are used to help determine the vernal point. I do appreciate your reply. Very best regards, Ed K PS. I hope you will enjoy the return of more reasonable temps up there in Minneapolis! > It's one thing for a scholar to see it and > something else again for a long-time tropicalist (as Fagan had been > since 1916) to make the leap, because first he had to understand it. Quote Link to comment Share on other sites More sharing options...
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