Roger: now that I've got the solar-eclipse problem solved, is there an equivalent book for lunar eclipses? BTW, while I'm using the full VSOP87D theory to predict the position of the Sun, it turns out that I can get quite respectable results using the simplified model of the Sun's longitude that appears in Meeus's "Astronomical Algorithms". (For the position of the Moon, I'm using Meeus's model in "Algorithms"). Also, the besselian elements as recorded in Meeus's "Elements of Solar Eclipses" are (in the case of the variables x, y, and d) computational overkill. The quadratic and cubic terms for x and y are 5 orders of magnitude smaller than the linear term, and for d, the quadratic term is always very close to zero. This shows that it's really safe to ignore those terms, which I've chosen to do with no ill effects. I've compared the maps I get to those on the NASA website and they're (visually at least) indistinguishable. Brad
On Tue, Dec 22, 2009 at 6:00 PM, Roger W. Sinnott <rsinn...@post.harvard.edu > wrote: > Brad, > > No, Meeus's Elements of Solar Eclipses book does not tell how to calculate > the Besselian elements. Rather, it LISTS these elements for all solar > eclipses from 1951-2200. Its real strength is that it provides detailed > numerical examples of how to USE these elements to calculate the path of > totality (northern and southern edge), as well as the appearance, > magnitude, > contact times, and limit curves of the partial phases. It also explains > how > to determine the circumstances of the eclipse at any specific latitude and > longitude. > > To calculate the Besselian elements themselves, if you want to, first you > need a source of highly accurate ephemerides for the Sun and Moon (such as > from the Astronomical Almanac, NASA's Horizons, or Aldo Vatagliano's Solex > shareware program). Then you need the algorithms for deriving the > elements. > These are given is such places as the Explanatory Supplement to the > Astronomical Almanac (either the 1992 or 1961 edition), or William > Chauvenet's Manual of Spherical Astronomy (various editions, 1863 to 1891; > also reprinted by Dover in 1960). Calculating the elements is actually > more > straightforward than using them to get accurate local preditions and curves > for an eclipse. > > -- Roger > > > ----- Original Message ----- > From: "Brad Lufkin" <bradley.luf...@gmail.com> > To: "Sundial Mailing List" <sundial@uni-koeln.de> > Sent: Tuesday, December 22, 2009 3:07 PM > Subject: Re: Nasa website > > > > Speaking of Meeus, does anyone know if his "Elements of Solar Eclipses" > > includes algorithms for calculating the Besselian elements of eclipses or > > just presents tables of results? Also, does the book present algorithms > > for > > calculating the paths of eclipses? It's not clear from the description on > > the bookseller's website. > > Regards, Brad > > --------------------------------------------------- > https://lists.uni-koeln.de/mailman/listinfo/sundial > >
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