NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Real accuracy of the method of lunar distances
From: Fred Hebard
Date: 2004 Jan 14, 18:29 -0500
From: Fred Hebard
Date: 2004 Jan 14, 18:29 -0500
I responded earlier today to Jared's message, but only to him, for some reason. It didn't help that I recarved my HD today. But I did mess up my reply so this is a chance to set it straight. Fred >those times when the Apparent > Moon is moving more slowly? Those times are when the Moon is highest > in the > sky. If you can answer that question, you have settled the argument.> > [Geo. Huxtable] > > > Ah, a crux. I'm afraid even I may be understanding this thanks to all > the patient re-explanations. > > > For the sake of simplicity, I think we can for a moment ignore the > question of whether/when the moon appears to move more rapidly against > the stars, and stick to the crux of things. > > > Perhaps we could perform a simple exercise here: > > > Assume that I take a lunar distance measurement at 5:30AM. And then > again at midnight. > 1-How long does it take me to take the lunar, i.e. to measure the > distance from the moon to the other body? > Is that "instantaneous" observation affected by the speed of the > moon's motion? no > > 2-Am I doing anything else, which is not "instantaneous", which will > be affected by the "speed" of the moon? no > 3-Bottom line time. Perform the above observations and timings, > assuming both the fastest and slowest "speed" of the moon for the > readings when the moon is overhead, and on the horizon. Clear the > lunars from both times. (Or all three, to use both horizons.) Are the > results ANY different, allowing for a different speed of the moon? no > And if #3 seems unclear, that's because I'm not familiar with the > mechanics of clearing a lunar, so please feel free to re-structure the > experiment allowing for the realities of the process. Theories are > fine, but what are the actual numbers? How does the presumed change in > lunar "speed" affect readings, if it does at all? To what amount of > time? Five seconds? One? Just what IS the magnitude of error that we > are chasing here? zero