NavList:

-------------- Original message from Alexandre E Eremenko <eremenko@math.purdue.edu>: --------------


> Joel,
> Thanks. It seems to me that in both cases it is the
> diameter of the telescope objective lens that is most relevant.
> Provided that the mirror occupies the whole field of view.
> Indeed, once this is the case,
> increased mirror will not send more light
> into the scope. Same about motion.
>
> So you probably mean that in the old sextants with small mirrors
> the mirrors did not occupy the full field of view,
> and some of this field of view was thus wasted, correct?
>
> Alex.
>
>
> On Tue, 11 Oct 2005 joel-jacobs@att.net wrote:
>
> > Hello Alex,
> >
> > Large mirrors collect more light and transmit more though the op! tics which are
> an advantage in taking twilight sights.
> >
> > The second adavantage is that celestial objects tend to move around on the
> horizon mirror due to the motion of the vessel or of the sight taker. They also
> seem to move more when taking high altitude sights. The larger size mirrors
> provide more surface area for the body to dance on before being lost from view.
> >
> > Also try WD 40, a moisture displacement chemical, to minimize affects of
> spray.
> >
> > Joel
> > --
> > Visit our website
> > http://www.landandseacollection.com
> >
> >
> >
> >
> > -------------- Original message from Alexandre E Eremenko
> : --------------
> >
> >
> > > Dear Joel,
> > >
> > > > 1. The larger the size of the! mirrors, the better.
> > >
> > > I always read and hear this, but I am not sure that
> > > I understand exactly why the larger mirrors are better.
> > > Can you explain?
> > >
> > > > 2. Sextants with enclosed tangent screws
> > > > are prone to having them freeze
> > > > unless they are cleaned after use when
> > > > there is spray.
> > >
> > > This I confirm, even with my small experience.
> > > The remedy is to wash it with fresh water after
> > > a spray. And the fresh water is sometimes scarce
> > > on a small boat.
> > >
> > > Alex.
>