A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Position-Finding
From: Paul Middents
Date: 2002 Jun 14, 15:46 -0700
I have just found a very interesting article which addresses Lewis and Clark's observational methods: “The Accuracy of the Astronomical Observations of Lewis and Clark”, Richard S. Preston, Proceedings of the American Philosophical Society, Vol 144, No. 2, June 2000
I am still absorbing the details but in summary, Preston determines why simultaneous altitudes were not measured in conjunction with the lunar distances. These altitudes were to be calculated from an assumed longitude and then used to clear the lunar distance of the effects of refraction and parallax. He finds that this method as recommended by Andrew Ellicott and Robert Patterson is technically correct. It should yield reasonable results with a single iteration for most cases. Had Lewis and Clark’s results been calculated, Most would have been reasonable.
He speculates why F.R. Hassler (Mathematics professor at West Point) might have given up in despair when trying to calculate from Lewis and Clark’s data. I was most surprised to find out that the data had never been computed.
Preston developed computer programs based on a method developed by Robert Bergantino of Montana, to calculate positions and finds that Lewis’ data supports positions within about 30 minutes of arc in longitude.
I find this article extremely interesting. It seems to solve a long standing mystery concerning Lewis and Clark’s methods and somewhat vindicates their observational ability.
I have followed the thread between George Huxtable and Bruce Stark on the question of calculated altitudes. Bruce is acknowledged by Preston in the article so I know he is familiar with this. I find no other reference to either Preston or Bergantino in the Navigation-L archives.
I would appreciate the opinion of the “lunarians” on this list of Preston’s work.
I would also like to express my appreciation and admiration for George Huxtable’s series, “About Lunars”.