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    Re: SNO-T "night" sight tube?
    From: Brad Morris
    Date: 2018 Nov 22, 16:46 -0500
    Tony 

    Kindly take an observation of the moon with the appropriate shades.  The moon's brightness should be attenuated such that the horizon is crisp.  Without sufficient shading, the brightness of the moon will blind the eye to the far less illuminated horizon.  With proper shading: Do you still see the inter-lens reflected blob?  Were you able to take the altitude?  

    If you find anti-reflective coatings useful, then by all means proceed.  Some modern sextants do have them.  

    Brad

    On Thu, Nov 22, 2018, 3:24 PM Tony Oz <NoReply_TonyOz@fer3.com wrote:

    Dear Brad,

    I  whether there should be any AR-coating because my newly-bought Galilean scope has a very bright spot/blot moving all over the field of view when I watch the Moon for example. This blot is there definitely because of internal reflexions within the lenses. It is so intensive that I guess it will make a lunar-distance sight more difficult. I asked amateur-astronomers about AR-coating and they confirm the image contrast is better if the coating is there.

    Warm regards,

    Tony

    60°N 30°E

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