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    Re: Dream Choice of Sextant
    From: Alexandre Eremenko
    Date: 2005 Aug 13, 11:33 -0500

    Mike,
    It is hard to describe.
    The only "scientific" objection I have is against
    all kinds of semi-transparent mirrors, because
    they decrease the amount of light necessary for
    twilight observations.
    Concerning the astigmatizers and the prisms,
    this is just a matter of feeling, I cannot put it in words.
    
    By the way, even celestaire advertisement (if I remember it correctly)
    warns that you should try the astigmatisor first, it is not
    to everyone's taste. I had some limited opportunity to try
    recently (from the Cassens and Plath office windows only)
    and I decided that I did not like any of their additions to
    their Basic Model.
    
    Alex.
    
    On Mon, 8 Aug 2005, Mike Hannibal wrote:
    
    > Hi Alexandre,
    >
    > my brain is addled - I meant Polaris. My apologies.
    >
    > I would be very happy if you would expnd further on
    > your views about the "gimmicks".
    >
    > Thanks
    >
    > Mike
    > --- Alexandre E Eremenko 
    > wrote:
    >
    > > Dear Mike,
    > > I've never heard of a C&P "Pelarus" sextant.
    > > Maybe you mean C&P Polaris?
    > > (A "star specialist" as they call it)
    > >
    > > I have a very limited experience with
    > > C&P sextants (once Fred Hebard let me try his,
    > > and recently I visited their factory where I had an
    > > opportunity to try them all from the window of their
    > > office).
    > > And I have to say that NONE of their sextants
    > > is my "dream sextant":-)
    > > In particular I was disappointed with all
    > > these gimmicks like astigmatizer,
    > > Schueler prism, and fancy horizon glasses.
    > >
    > > I strongly prefer to have a variety of scopes
    > > and eyepieces instead, an eyepiece filter
    > > and a simple "traditional" horizon mirror,
    > > which is most light-efficient of all of them.
    > >
    > > Alex.
    > >
    > > On Mon, 8 Aug 2005, Mike Hannibal wrote:
    > >
    > > > 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
    > > >
    > >
    >
    >
    > Send instant messages to your online friends http://au.messenger.yahoo.com
    >
    
    
    

       
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