NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Lunar distance accuracy
From: Frank Reed
Date: 2007 Oct 23, 21:20 -0400
From: Frank Reed
Date: 2007 Oct 23, 21:20 -0400
Jim you wrote: "Standing on land in good conditions, no averaging, I have found that obtaining sun moon lunars with an accuracy of <0.5' can be obtained routinely with many sights well within this. Using stars I would have to estimate a slight increase in error putting it at <0.7'. Using planets I find that getting reliable results consistently <1.0' is getting to be a challenge." My own experience is that I can get individual Sun-Moon lunars accurate with a standard deviation of about 0.25 minutes of arc. By averaging four in a row, the net accuracy is nearly doubled. Sun-star lunars are worse for the bright stars (e.g. Regulus) by a factor of two and for the fainter stars (e.g. alpha Arietis) by a factor of three. For the planets, I get excellent results with Jupiter, Mars when its bright, as it is now, and Venus when it does not have much phase. For all of these, especially Moon-Jupiter lunars, the results are just as good as the very best Sun-Moon lunars. I would recommend trying some more Jupiter lunars to see if you can improve your results. In the first month when I joined this group, nearly four years ago, I posted about Moon-Jupiter lunars. The thread starts here: http://www.fer3.com/arc/m2.aspx?i=012716&y=200312 Incidentally, when you look through old logbooks, you find that something like 80% of lunar observations were Sun-Moon, at least for American commercial vessels. Celestial navigation was largely a daytime activity in the 19th century. They also shot the standard lunars stars now and then, but I have not yet found a single attested Moon-planet lunar. I'm sure some navigators tried them, but since the ephemerides of the planets were less accurate back then, using them may have been seen as one more layer of uncertainty (which would have been true 175 years ago, but not today). -FER --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to NavList@fer3.com To , send email to NavList-@fer3.com -~----------~----~----~----~------~----~------~--~---
