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