NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Lunars using Bennett
From: Dave Walden
Date: 2008 Jul 3, 18:36 -0700
From: Dave Walden
Date: 2008 Jul 3, 18:36 -0700
George asks some quite 'to the point' questions: "Does Dave agree that a fair summary of his results would be that the vast majority of the calculations fall within a range of 2 minutes of arc?" Yes. "I expect that Dave Walden has been careful to avoid any interpolation in his automated procedure, but it would be useful to have that confirmed." Indeed no interpolation was done. It is in fact, when simulating tabular methods, very easy to carry more precision than one realizes or intends. Much can be hidden by spread sheet or computer output formats. Precsion can stay with a variable even if you don't see it. The program contains much use of the nint (nearest integer) function. This is how the precision of the table is replicated. "...Dave could only convert the angle-error to a time-error by presuming some mean value for the rate, such as 30 arc-minutes per hour." Not quite true. Since real ephemeris data was used, actual rates are available. "So I ask Dave to make it clear whether the end-result scatter was in the overall difference between cleared distance and predicted distance, both worked from the tables, or if it was just the scatter in cleared distance compared with a precise calculation from the astronomy." The cleared distances calculated using Bennett were compared to ephemeris values. Simulating almanac precision or simulating using tables to calculate lunar distances from RA's and Dec's would have "muddied the waters". All things are possible. The code is there for the interested student. --~--~---------~--~----~------------~-------~--~----~ Navigation List archive: www.fer3.com/arc To post, email NavList@fer3.com To , email NavList-@fer3.com -~----------~----~----~----~------~----~------~--~---