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Dear Modris,

This is an interesting question, but unfortunately at this time I have no other
inverting telescope except my SNO-T.
In it, the wires are attached to the front part of the telescope, so the wire 
is always in the focus of the
objective lens. I always thought that this must be the standard attachment, 
but I do not remember how it was attached in other
inverting scopes that I have seen.

To me this arrangement seems logical: you see the wires clearly when they are in the common focal plane
of objective and eyepiece lenses. When the observer's eye can has some "non-standard" refraction power,
any deviation of this power effectively changes the focal distance of the 
eyepiece. But the focal distance
of the objective lens is constant. Therefore the wires have to be attached to 
the front part which holds the objective lens.

Alex.
________________________________________
From: NavList@navlist.net [NavList@navlist.net]
Sent: Sunday, July 21, 2024 10:15 PM
To: Eremenko, Alexandre
Subject: [NavList] Re: Sextant Telescope

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Re: Sextant Telescope
From: Modris Fersters
Date: 2024 Jul 21, 12:20 -0700
Dear Alex, you wrote:
�When you focus on wires (so that they look as sharp as possible), then you automatically
focus on any remote object (Sun, Moon, a star or horizon).�
 I think you wrote this according to your expierence with SNO-T sextant�s 
inverting scope. Yes, indeed, it allows to focus the scope to the infinity, 
looking at the wires. As I mentioned in my previous post, in my SNO-T I find 
that I still need to finetune the focus slightly, when looking at celestial 
bodies. But it is maybe because of myopia.
In SNO-T inverting scope crosswires are not conected to adjustable eypiece. 
They are fixed to the main tube of the scope. Historic sextants had typically 
crosswires conected to the eypiece stacionary (it means, crosswires are 
always in focus, because the wires moves with eypiece every time we change 
focus).
Maybe you or other NavList members know: is there any other sextant model 
(except SNO-T), that has these wires fixed to the main tube (not to the 
eypiece tube)?
Modris Fersters




 

   

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