NavList:

Hello, Paul, Frank, Antoine!

I really admire your high level programming skills and detailed understanding of celestial mechanics. It is a rocket science for me. In relation to recent discussion of software accuracy I will write down some of my thoughts.

I can judge about one or other software only as ordinary, unpretentious user. I frequently use software to check the accuracy of my sextants and at the same time — my observation skills. I compare my observed angles with computer generated actual angles. I would like the software to be more accurat than the limits of sextant sights (0,1’) at least by factor of 2 or 3 (2”…3”)  Why should I add an additonal software error of 0,1’ or 0,2’ to my sextant observation errors? For lunars these errors are important. Each 0,1’ matters. I will be much happier to know I was off by 0,3’ than 0,5’. This is something like sports competition where even seconds or fractions of seconds can change the winner.

This is a question why do I need certain accuracy. In historical lunars even temperature and preasure were frequently ignored. And oblateness of the Earth (typically about additional 0,1’ error). But this was because of practical purposes—to do all the math faster. But computer does not get tired doing some additional mathematical operations.

But is it possible to get 2”…3” accuracy out of the software? I don’t no. This is a question to experts (to you). As far as I understood, Frank thinks that this is impossible. Paul and Antoine thinks it is possible.   

Frank’s lunar calculator after the last updates differs from Lunar4.4 in some cases 0,13’ (I checked only some examples). If I understand correctly, Frank’s philosophy is not to try achieve higher accuracy than 0,1’-0,15’ (Frank, please correct me, if I am wrong). Paul’s philosophy is different. He tries to get out of his software the limits of the possible.

Your professional discusions are indeed very interesting and educational. I am looking forward to hearing from you again.

Modris Fersters