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From: George Huxtable (no email)
Date: Wed May 10 2006 - 17:20:26 EDT
It seems that message distribution from Nav-l is
still failing.
The following message (copied again below) was
sent several
hours ago. Normally, I would expect to get a copy
reflected back from Nav-l rather promptly. But
none has arrived here.
It was certainly received and posted up, because
GregR has since responded to it.
If I have failed to receive it, perhaps others
have as well. That's why I am resending the
message, and will keep on resending until I
receive a copy.
Of course, it doesn't matter, to me, whether I
receive that message or not, because I know what's
in it. But knowing that that one was lost, how
many others have failed to get here, that I am
unaware of? It's a serious problem, that calls for
attention.
| On May 03, GregR asked-
|
| "I bought a Mk 25 sextant a couple of weeks ago,
| and am wondering about the accuracy of the beam
| converger (it's a full-horizon model vs.
| split-mirror) "
|
| I think between us Nav-L members have resolved
| GregG's problems for him, but it may be worth
| discussing again the values of what Davis call a
| "beam-converger", and others call a full-horizon
| or full-view mirror, as opposed to the
traditional
| half-horizon mirror, silvered across only half
its
| width.
|
| What's brought it to mind is a thoughtful note,
| (together with an abstract of the Davis patent
| about their version) in the Spring issue (No 91)
| of "The Navigator's Newsletter", by its new
| Editor, David Burch (of Starpath). That
quarterly
| journal, issued to members of the Foundation for
| the Promotion of the Art of Navigation, has been
| through a very lean patch, but has recently been
| thoroughly transformed, I'm pleased to say.
|
| A few Nav-l members pop up in that journal. For
| example, Bill Murdoch (a name familiar to Nav-l
| readers) has contributed about that Davis
patent.
|
| I won't copy details of that note, except
David's
| "nutshell summary", which goes as follows-
|
| "Full-view mirrors make the easy sights easier,
| and the hard sights harder."
|
| That view corresponds exactly with the reports
of
| the "traditional" navigators, using lunar
| distances, in the 2001 re-enactment for the BBC
of
| a leg of Cook's first circumnavigation. They
found
| that in daytime a high, pale, Moon was invisible
| against a milky sky using a full-view mirror,
but
| showed up clearly with a split mirror. It was a
| question of contrast.
|
| For anyone interested, the foundation is run by
| Terry Carraway, and the subscription for members
| in the US is (I think) $30. The website address
| is-
| www.navigationfoundation.org
| the address is PO box 1126, Rockville, Maryland
| 20850, USA.
| Phone or fax is 301-622-6448
| for emails.
|
| George Huxtable.
|
| contact George Huxtable at
|
| or at +44 1865 820222 (from UK, 01865 820222)
| or at 1 Sandy Lane, Southmoor, Abingdon, Oxon
OX13
| 5HX, UK.
|
|
|