NavList:

   

Reply

Dear Fred,

On Fri, 22 Feb 2008, Fred Hebard wrote:

> I'm mostly resisting any national comparison jokes here.

I did not understand this remark. Would you explain,
perhaps off-the-list?

Alex.

> On Feb 22, 2008, at 10:38 AM, Alexandre E Eremenko wrote:
> > George,
> >
> >> What struck me was its rather strange
> >> (to me) construction, in that the
> >> index arm swings on the "wrong" side of the frame;
> >
> > This is not exactly so. The arm moves INSIDE the frame.
> > If you look carefully you see that the frame has
> > a complicated shape which allows the arm to move
> > inside. The handle is attached to the
> > "other part of the frame", behind
> > the arm. Of course you can call the part of the
> > frame behind the arm a bridge, but it is an integral
> > part of the frame. The purpose of this
> > arrangement is to protect the arm.
> >
> > Freiberger has similar construction of the frame.
> > In general Freiberger looks very similar, except
> > it does not have the inverting scope and does not
> > have the scale magnifier/illumination device.
> >
> >> I ask those familiar with this
> >> instrument whether they see any
> >> advantage in the straight-through, inverting,
> >> 6x telescope, compared with an
> >> equivalent, non-inverting, prismatic ocular
> >> of similar power and
> >> light-grasp? Presumably,
> >> the prismatic would be a bit heavier; are there
> >> other differences?
> >
> > It is very much lighter, and lets more light through.
> > In this telescope, the light passes through only two lenses.
> > All astronomical telescopes-refractors are made this way,
> > and the reason is to minimize the loss of light.
> > So the designers of this telescope surely had the
> > same reason.
> > In addition, this is the only "modern" sextant telescope
> > that has wires. Wires are handy for many adjustments,
> > and make it easier to hold the object in the center of
> > the field.
> >
> > In the old days (until approx. 1940-s) many sextants had
> > inverting scopes with wires. However the SNO scope has
> > a substantial advantage in comparison with these old
> > scopes: much larger field of view, and much larger
> > diameter of the objective lens. Again this lets more
> > light through.
> >
> > Alex.
> >
> >
> >
> > >
>
>
>
> >


--~--~---------~--~----~------------~-------~--~----~
To post to this group, send email to NavList@fer3.com
To , send email to NavList-@fer3.com
-~----------~----~----~----~------~----~------~--~---

   

Reply