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Sunday, July 24, 2005
Your Sky: Asteroid and Hyperbolix
No, not them! I've integrated the Landgraf/Stumpff algorithm for determination of the position of bodies on parabolic and hyperbolic orbits into Your Sky, which permits computation of the position of all catalogued objects on hyperbolic heliocentric orbits. (Such bodies are rare--all are comets whose orbits have been perturbed by planets during their most recent passage through the solar system to put them on an escape trajectory.) The algorithm handles eccentricities as great as 1.1, which more than suffices since no object in the JPL catalogue of comets with well-known orbital elements has an eccentricity as high as 1.06. To demonstrate, you can plot the current position of Comet Bowell (C/1980 E1) which, with an eccentricity of 1.056, has the most hyperbolic orbit of any catalogued comet. Earlier versions of Your Sky would have abandoned the calculation of the position of this comet upon discovering it was on an escape trajectory, while the new release correctly plots it receding into the void more than one and half times the distance of Pluto from the Sun.Posted at
23:09
Reading List: Aagaard's Africa
- Aagaard, Finn. Aagaard's Africa. Washington: National Rifle Association, 1991. ISBN 0-935998-62-4.
- The author was born in Kenya in 1932 and lived there until 1977 when, after Kenya's ban on game hunting destroyed his livelihood as a safari guide, he emigrated to the United States, where he died in April 2000. This book recounts his life in Kenya, from boyhood through his career as a professional hunter and guide. If you find the thought of hunting African wildlife repellent, this is not the book for you. It does provide a fine look at Africa and its animals by a man who clearly cherished the land and the beasts which roam it, and viewed the responsible hunter as an integral part of a sustainable environment. A little forensic astronomy allows us to determine the day on which the kudu hunt described on page 124 took place. Aagaard writes, "There was a total eclipse of the sun that afternoon, but it seemed a minor event to us. Laird and I will always remember that day as 'The Day We Shot The Kudu'." Checking the canon of 20th century solar eclipses shows that the only total solar eclipse crossing Kenya during the years when Aagaard was hunting there was on June 30th, 1973, a seven minute totality once in a lifetime spectacle. So, the kudu hunt had to be that morning. To this amateur astronomer, no total solar eclipse is a minor event, and the one I saw in Africa will forever remain a major event in my life. A solar eclipse with seven minutes of totality is something I shall never live to see (the next occurring on June 25th, 2150), so I would have loved to have seen the last and would never have deemed it a "minor event", but then I've never shot a kudu the morning of an eclipse! This book is out of print and used copies, at this writing, are offered at outrageous prices. I bought this book directly from the NRA more than a decade ago--books sometimes sit on my shelf a long time before I read them. I wouldn't pay more than about USD 25 for a used copy.
Posted at
01:05