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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Exercise #6, Lunars at sea
From: Jeremy C
Date: 2008 Jun 4, 02:51 -0700
From: Jeremy C
Date: 2008 Jun 4, 02:51 -0700
Frank Wrote: > Notice how averaging would help you here. The errors in the LD's are -0.3, > +0.7, -0.4. And the average is [drum roll, please...] exactly ZERO! This is > partly accidental in this case, of course, but you will find that the > results are almost always better when you average a set of three to five. > Averaging the errors after the reduction is not quite the same as averaging > the sights and times before reduction, but it's nearly so. And just to > reiterate, this was the normal historical approach. > What is the traditional means of averaging? Do you average the time and then the LDs and just do one reduction? I have never averaged sights really except to reduce 3 sunlines, plot them, and find a midpoint. > By the way, if you want to think about lunar distance observations > differently, each lunar generates a line of position, which you could plot > on a chart just like any other LOP. But unlike standard altitude LOPs, an > error of 0.1 minutes of arc in a lunar distance observation implies a 6 n.m. > error in the lunar LOP. One advantage is that you can shoot lunars when the > horizon is hidden. Cross two lunar LOPs and you get a rough position fix. I would like to try this, but am not sure how you do it. Lunars are my weak point in Celnav, and I can hardly get them shot and reduced, let alone do something exotic with them as make an LOP. Jeremy --~--~---------~--~----~------------~-------~--~----~ Navigation List archive: www.fer3.com/arc To post, email NavList@fer3.com To , email NavList-@fer3.com -~----------~----~----~----~------~----~------~--~---