Next message: Alexandre E Eremenko: "Re: Suitable Sextants"
Alex,
Sometimes the proof of the pudding is in the eating.
Take a proper Star scope and couple it with a small size horizon mirror, and note the results at twilight.
Also take a sextant with small mirrors and use what ever scope you are most comforatble with and try some high altitude sun sights. Note the results.
I suggest it will be like your use of an inverting scope on land vis-a-vis at sea.
You never notice the difference until you're at sea.
Joel
--
Visit our website
http://www.landandseacollection.com
-------------- Original message from Alexandre E Eremenko <>: --------------
> 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 wrote:
>
> > Hello Alex,
> >
> > Large mirrors collect more light and transmit more though the optics 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.
>
