Hello Jos My best guess is that your observing instrument is corrupted. Use spirit level and test at least, if its inclinations are correct. You could also test your calculation rutines using tabulated values to be sure your method is sound. And finally, thank you for your hint. I think I will also try the problem but I think to start with the precalculated tabulated values.
Aimo Niemi http://pc-calculator.110mb.com/gnomon/ 2009/1/5 Jos Kint <[email protected]> > Hello sun dialists, > > I have a question. As I said some months ago I want to calculate the > earth's orbital eccentricity, using my sun dial. I tried it in two ways. > First I followed the suggestion of Chris Lusby Taylor and used the Ptolemy > model after finding aproximate values for the vernal equinox, the summer > solstice, the autumnal equinox and now recently of the winter solstice. My > observed values had an error of about ten hours. Using these inaccurate > values in the Ptolmy model gave me an e=0,0173. Not bad but also not very > good. > At the same time I used a formula, given by my friend Stan Ulens in which > the total EOT was split in a contribution EOT1 due to the angle made by the > ecliptica and a contribution EOT2 due to the eccentricity. After about 200 > observations during 8 months, I got three weeks ago a mean value e= 0,01671! > However things started to go wrong after 13 december. The values of e in > december skyrocketed to e= 0,0378 and even e= 0,0414. > > Who has done similar work? What are the results? Who can give reasons for > my rather bad experience in December? I can measure the solar altitude with > an error of about 1 minute and the solar time with an error of about 1 > minute > > > Jos > > [email protected] > > --------------------------------------------------- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > >
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