NavList:

I received an email from a former NavList member, a couple of days ago.

He quoted me as follows:
"For lunars today, using a well-adjusted sextant with a 7x scope (with good weather, on land), I get a typical standard deviation on individual lunars of about one-quarter of a minute of arc --roughly two-thirds of my individual lunars are as accurate as that."

And then he wrote:
"You won't want to know. Nor care. But I would like YOU to know...
I SIMPLY DON'T BELIEVE YOU.
I would concede an SD of +or- half a minute of arc might just be possible in perfect conditions - but pushing it at that. I think you are peddling snake-oil.
No need to reply - you would be wasting your time."

Note: I have replaced the bold italicized words in his original email with upper case here. For those of you who were not following NavList messages from June 2009 through October 2010, you may not recognize the style. Others will surely know that this was from that most miserable of online character-types, a "know-nothing know-it-all". He ranted about the accuracy of lunars in October 2010 but based his conclusions on incompetence at every level: in his observations and in his calculations, too.

Nonetheless, I post this because I think it's an interesting expression of the degeneracy into which celestial navigation has fallen. There are people who are so incompetent at adjusting and using their sextants and working even the simplest of calculations that they actually do not believe it is physically possible to measure angles with a standard deviation of a quarter of a minute of arc. In another fifty years, pseudo-historians of the subject will probably be writing that celestial navigation was never more accurate than 10 nautical miles, but hey, that's "good enough" for those twentieth century primitives.

I repeat a little challenge I made earlier. Can you measure the diameter of the Sun today (or in the next few days), now at its largest for the year? Get out your sextant and give it a try. How close are you to the correct value? Do you get better results with a more powerful scope? If you're way off, where do you think you're losing accuracy?

-FER

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