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A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Sextant infos
From: Glendon
Date: 2002 Jan 30, 1:45 AM
From: Glendon
Date: 2002 Jan 30, 1:45 AM
Hi Pierre and group, From my watching of Russian sextants, here are my unauthoritative views: The SNO-T and SNO-M (earlier SNO) are quite different sextants. The SNO-T invariably came with 2 scopes ( one Gallilean), most SNO-M with 1, but some with 2, and the SNO with 1. The SNO-T seems to be modelled on a late fifties early sixties Freiberger, the SNO(-M) on a Plath, probably thirties or forties. The frame construction and the screw mechanism are quite different between the two. The optics look similar, from photographs I have seen. I have a 1968 SNO-T in virtually unused condition...the optics are excellent, the errors are minimal, its a joy to handle...by which I mean the feel is great, although a bit light for some perhaps. I am very interested in acquiring a SNO(-M) !!! So, let us know how yours goes. Lee Martin ----- Original Message ----- From "Pierre Boucher"To: Sent: Wednesday, January 30, 2002 3:17 PM Subject: Re: Sextant infos > >this is a Russian Cetus sextant. I have one. > >There should be 2 telescopes. One with cross-hairs which also magnifies - I > >will have to get mine out to see hat the magnification is... (i'm writing > >this from my office). The second eyepiece shows the image the correct way > >around. > > Thanks to Aubrey for the infos. > > There is only 1 telescope (and support for it) in the box (magnifying with > cross-hairs). No other support for an extra eyepiece. > I saw some pictures on the web SNO-T model with 2 eyepieces and SNO-M with > only one. Maybe the other eyepiece could be bought seperately,... somewhere! > > Pierre Boucher > > ************************************************************************** > X > XX X Pierre Boucher N > XXX XX formation en navigation de plaisance > XXXX XXX Ste-Therese (Quebec) Canada > XXXXX XXX > XXXXXX XXX la "VOILE"... le reste n'est que du vent... > XXXXXXXXXXXXXX ''Sail, Sail !''... the rest is only wind > XXXXXXXXXXXX > XXXX EMAIL: pboucher@lavoile.com > XXX "http://www.lavoile.com" > ************************************************************************** >From- Navigation Mailing List [NAVIGATION-L@LISTSERV.WEBKAHUNA.COM] on behalf of Glendon [glendonJLM@BIGPOND.COM] Sent: Wednesday, January 30, 2002 1:54 AM To: NAVIGATION-L@LISTSERV.WEBKAHUNA.COM Subject: Re: Sextant infos Errk.....make that a 1986 model that I have!! The SNO-M and SNO-T overlapped between the late sixties and early seventies, I think. Lee Martin ----- Original Message ----- From "Glendon" To: Sent: Wednesday, January 30, 2002 7:45 PM Subject: Re: Sextant infos > Hi Pierre and group, > > From my watching of Russian sextants, here are my unauthoritative views: > > The SNO-T and SNO-M (earlier SNO) are quite different sextants. The SNO-T > invariably came with 2 scopes ( one Gallilean), most SNO-M with 1, but some > with 2, and the SNO with 1. The SNO-T seems to be modelled on a late fifties > early sixties Freiberger, the SNO(-M) on a Plath, probably thirties or > forties. The frame construction and the screw mechanism are quite different > between the two. The optics look similar, from photographs I have seen. > > I have a 1968 SNO-T in virtually unused condition...the optics are > excellent, the errors are minimal, its a joy to handle...by which I mean the > feel is great, although a bit light for some perhaps. I am very interested > in acquiring a SNO(-M) !!! So, let us know how yours goes. > > Lee Martin > ----- Original Message ----- > From- "Pierre Boucher" > To: > Sent: Wednesday, January 30, 2002 3:17 PM > Subject: Re: Sextant infos > > > > >this is a Russian Cetus sextant. I have one. > > >There should be 2 telescopes. One with cross-hairs which also magnifies - > I > > >will have to get mine out to see hat the magnification is... (i'm writing > > >this from my office). The second eyepiece shows the image the correct way > > >around. > > > > Thanks to Aubrey for the infos. > > > > There is only 1 telescope (and support for it) in the box (magnifying with > > cross-hairs). No other support for an extra eyepiece. > > I saw some pictures on the web SNO-T model with 2 eyepieces and SNO-M with > > only one. Maybe the other eyepiece could be bought seperately,... > somewhere! > > > > Pierre Boucher > > > > ************************************************************************** > > X > > XX X Pierre Boucher N > > XXX XX formation en navigation de plaisance > > XXXX XXX Ste-Therese (Quebec) Canada > > XXXXX XXX > > XXXXXX XXX la "VOILE"... le reste n'est que du vent... > > XXXXXXXXXXXXXX ''Sail, Sail !''... the rest is only wind > > XXXXXXXXXXXX > > XXXX EMAIL: pboucher@lavoile.com > > XXX "http://www.lavoile.com" > > ************************************************************************** > >From- Navigation Mailing List [NAVIGATION-L@LISTSERV.WEBKAHUNA.COM] on behalf of Chuck Griffiths [griffiths_chuck@SI.COM] Sent: Wednesday, January 30, 2002 7:30 AM To: NAVIGATION-L@LISTSERV.WEBKAHUNA.COM Subject: Re: Fluxgate compass OK, I'll throw in my fluxgate question that has been eating at me since I installed a fluxgate for my autopilot a couple years ago. When one first installs a fluxgate, I would imagine that it has two errors. First, when the ship is on a heading of exactly "0", relative to local variation, the fluxgate reads something other than north, due to deviation (the disturbance of the sensor by magnetic fields on the ship). Second, all other headings will also have deviation induced errors, e.g. the display indicates 80 degrees when it should read east. Now, I can imagine that after the compensating program is run, the fluxgate could compare the rate of turn indicated during the compensating turns and adjust indicated headings such that they match headings as they should have appeared during the turns. To continue my example, the fluxgate could sense the rate of turn and know that 90 degrees of turn have been completed so the display should indicate east, the previous error between 80 and 90 degrees could be corrected. But, how does making constant rate turns help the fluxgate find magnetic north if it sensed it incorrectly to begin with? Of course, I checked it after I corrected it by comparing headings to sun bearings so I know it works, I'm just wondering if someone can explain how it works. ____________________Reply Separator____________________ Subject: Re: Fluxgate compass Author: Brian Whatcott Date: 1/29/02 6:33 PM At 05:16 PM 1/29/02, you wrote: >... What exactly >is a bolt-down sensor? And what errors does it "abolish"? > >As I understand it, a fluxgate compass, like any other compass, needs to >establish the direction of the horizontal component of the Earth's field, >with respect to the direction of the vessel. For this to happen, somehow >the fluxgate compass, just like any other compass, has to be aware of the >direction of the horizontal. ... >George Huxtable. George, the comments I posted were on the basis of examining the constructional details of a fluxgate. In view of your praiseworthy efforts in describing the Lunar, I'll try to return the favor by taking a look at what the commercial fluxgate offerings provide. It may be that for a 2-axis fluxgate, a pendulous mount might be adopted. This would retain the pendulous errors associated with a compass card of the conventional kind. I'll get back to the list, if I find useful engineering input. A three axis fluxgate can be mounted rigidly. This is sometimes called a 'bolt-down' sensor. ********************************************************************** This e-mail and any files transmitted with it are confidential and may be legally privileged or otherwise exempt from disclosure under applicable law. This e-mail and its files are intended solely for the individual or entity to whom they are addressed and their content is the property of Smiths Aerospace. If you are not the intended recipient, please do not read, copy, use or disclose this communication. 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