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    Re: Dream Choice of Sextant
    From: Alexandre Eremenko
    Date: 2005 Aug 10, 13:23 -0500

    After having tried a few full size brass sextants
    (C. Plath, Cassens-Plath, several Hughes and
    others) I am inclined to like aluminium alloys
    as preferred material.
    It seems that Fred Hebbard tends
    to agree after his trial of my SNO.
    
    (The duralumin sextants I know are
    Freiberger, Tamaya, and SNO-T).
    
    The main advantage of aluminium alloys is their light
    weight. In addition, Hughes, in his advertisement
    of 1930-s says that duralumin has advantages
    (in comparison with "gun metal", he means brass, as
    I understand) in mechanical characteristics.
    
    Alex.
    
    On Mon, 8 Aug 2005, Yourname Here wrote:
    
    > FYI,
    >
    > There were a few British sextants made in Sterling Silver.
    >
    > Joel Jacobs
    > --
    > Visit our website
    > http://www.landandseacollection.com
    >
    >
    >
    >
    > -------------- Original message from John Simmonds : --------------
    >
    >
    > biggest problem with stainless steels is cost of manufacture, and don't kid 
    yourself that it would be corrosion free :)
    > the thing would also be very heavy
    > John
    > live every day like it may be your last .. cause one day it will be
    >
    >
    > On Mon, 8 Aug 2005 07:39:51 -0400, Robert Eno wrote:
    > > I know my choice lies outside the bounds of what you described but
    > > my dream choice of sextant would be a C.Plath design in which all
    > > of the components are constructed from 316 stainless steel. I often
    > > wonder why no one ever thought of using this material for a
    > > sextant. Perhaps because it cannot be cast or perhaps because
    > > stainless steel is more prone to thermal changes than bronze or
    > > brass.
    > >
    > > Robert
    > >
    > >
    > > ----- Original Message -----
    > > From: "Mike Hannibal" 
    > > To: 
    > > Sent: Monday, August 08, 2005 2:43 AM
    > > Subject: Dream Choice of Sextant
    > >
    > >
    > >> If you had a choice between a C&P Horizon Ultra and a
    > >> C&P Pelorus which would you choose? Money isn't the
    > >> issue.
    > >>
    > >> The use is the full breadth of uses to which you might put a
    > >> sextant with an equal balance between
    > >> star/planet sights, sun sights and coastal nav stuff - distance
    > >> off, horizontal bearing etc.
    > >>
    > >> For those unfamiliar the key differences between the
    > >> two instruments are:
    > >>
    > >> 1) both use the same frame and "running gear";
    > >>
    > >> 2) the Horizon Ultra has a whole horizon mirror,
    > >> polarisers in both sets of shade glasses and
    > >> Schueler's double prism to get verticality right. In
    > >> other words it's a specialist sun machine;
    > >>
    > >> 3) the Pelorus has standard shades, an astigmatiser
    > >> for stars and planets, and an unusual horizon mirror
    > >> that is about 70% silvered in the a centre vertical
    > >> strip and unsilvered on either side. It is designed to be very
    > >> effective with dim stars but still OK brighter objects.
    > >>
    > >> I guess my current thinking is that the polarisers are nice and
    > >> make sun brightness and horizon clarity very easy to get just
    > >> right but that the Polaris is
    > >> proabably better for stars as it isn't hampered by the known
    > >> issues of a whole horizon mirror. On balance what I want is the
    > >> Pelorus with the polarisers as
    > >> well. I expect that verticality of the instrument will not be an
    > >> issue when using the astigmatiser but that
    > >> you'll just have to rock like you always do when doing sun/moon.
    > >>
    > >> Love to hear your views, and particularly if anyone
    > >> has used the Polaris or the Horizon Ultra.
    > >>
    > >> Regards
    > >>
    > >> Pelorus
    > >>
    > >> Send instant messages to your online friends
    > >> http://au.messenger.yahoo.com
    
    
    

       
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