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    Re: Sextants with Polarizing filters
    From: Peter Fogg
    Date: 2006 Jan 25, 13:46 +1100

    Which sextant is this, Mike?


    Did the polarising filters come as standard? If not, how did you add them?


    From: Navigation Mailing List [mailto:NAVIGATION-L@LISTSERV.WEBKAHUNA.COM] On Behalf Of Mike Hannibal
    Sent: Wednesday, 25 January 2006 1:28 PM
    Subject: Re: Sextants with Polarizing filters


    I use a sextant with a polarising filter on both the index and the horizon glass. They provide excellent filtering and I often use them alone - no other shade glasses. They are, as has been noted easily adjustable so it's easy to get specific brightnesses. This is particularly good when doing lunars - you can balance very easily the relative brightness of the other object with the moon.

    It is important to note however that even good polarisers change the index error when used. I know that the manuals say that this can happen with any shades but I have only ever measured it with polarisers - maybe it has to do with the two pieces of glass in each filter. In any event IE must be measured with the filters in place - orientation does not seem to matter.



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