Next message: Bill: "Re: Suitable Sextants"
Joel,
Yes, you are right.
Most of my experience was from land.
And on a small boat (not so small, 42 feet)
at first I could not use any scope at all,
just had to do it without scope (and with poor results).
A.
On Tue, 11 Oct 2005 wrote:
> 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.
> >
