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Re: Dream Choice of Sextant
From: John Simmonds
Date: 2005 Aug 9, 00:27 +1000
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" <pelorus32@YAHOO.COM.AU>
> To: <NAVIGATION-L@LISTSERV.WEBKAHUNA.COM>
> 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
From: John Simmonds
Date: 2005 Aug 9, 00:27 +1000
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
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" <pelorus32@YAHOO.COM.AU>
> To: <NAVIGATION-L@LISTSERV.WEBKAHUNA.COM>
> 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