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    Re: SNO-T "night" sight tube?
    From: Alexandre Eremenko
    Date: 2018 Nov 23, 06:47 +0000

    Dear Brad,
    You wrote:
    > When observing the bright object (sun, moon, planet, star) it should be 
    centered in the optics.  I have scopes which have crosshairs to help insure 
    the object is centered. 
    By the way, crosshairs are only possible in Kepler scopes. Not in Galileo scopes.
    You also wrote:
    > From a brief investigation, I get that AR was commonly available from the 
    1930's or 1940's.  I most certainly could be wrong about that, but it looked 
    like a WW2 enhancement.
    I do not remember an exact references, but I read somewhere that it was 
    invented by Germans (Zeiss) shortly before WWII.
    The main producer of Soviet optics after WWII was the company called LOMO 
    (Leningrad optico-mechanical union)
    which used German know-how and equipment. Lens of SNO-T telescopes were apparently made by LOMO.
    >   What of all the sextants manufactured before AR?  Am I to understand that 
    these devices are incapable of an observation?  Clearly they are not.
    Certainly they are not. AR probably gives a slight improvement in twilight 
    observations, better horizon visibility.
    I think that after 1940s or 1950s all binoculars have AR optics.

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