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Dave:

The issue here is consistency.  John said he had taken "over a thousand
sights" while rarely getting errors of less than three miles.  Assuming
John took these sights at different times of the year over a period of
years, I can't imagine a consistent meteorological problem such as your
friend described.  If one has done enough sights one has certainly
experienced fuzzy horizons due to humidity and haze.  But one has also
experienced wonderful, crisp, CAVU days where it's really doubtful that
one is getting anything less than a perfect horizon.

Lu Abel

Dave Weilacher wrote:
> A retired US Navy Commander friend who was reponsible for navigation aboard 
ship on one of his assignments is of the opinion that the horizon is always 
suspect near shore.  The argument is that the differences in temperature 
between land and sea screws up the horizon that you see.
>
> Could this account for the discrepancy between every ones expectations and his measured results?
>
>
>
> -----Original Message-----
> From: Carl Herzog 
> Sent: Jun 9, 2005 4:26 PM
> To: NAVIGATION-L@LISTSERV.WEBKAHUNA.COM
> Subject: Re: Plastic sextants. was: GPS shortcomings.
>
> George Huxtable wrote:
>
>
>>I'm rather surprised that John Kabel experienced such large errors, when
>>using his Astra from a beach (about 50 % within 3 miles). Was this
>>shot-to-shot scatter? How repeatable was a series of repeated shots at
>>close intervals? It could be explained by days of anomalous dip, but a 50%
>>frequency seems absurdly high. Does John have an explanation?
>>
>
> I'm curious too. Results like that do not reflect the inherent
> capability of the sextants. I've never had results that bad with either
> a plastic Davis or a metal Astra underway on any size vessel. I've never
> tried shooting anything from the shore, so I don't know what other
> factors may confound accuracy there, but it seems like something else is
> wrong in this case.
>
> Carl
>
>
> Dave Weilacher
> .IBM AS400 RPG contract programmer
> .USCG Master lic. 100 ton
> .ASA Sailing Instructor Evaluator
>
>

   

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