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    Re: Sextants with Polarizing filters
    From: Mike Hannibal
    Date: 2006 Jan 25, 13:58 +1100
    C&P Horizon Ultra - Mike H Special!

    The Horizon Ultra comes with one on the horizon glass I think. I asked for an extra to be added on the index mirror. The horizon glass is also different. A vertical strip down the centre has quartz coating so that it's a "whole horizon" style mirror and the outsides are clear glass - works brilliantly. Sheer indulgence but it's good!



    Peter Fogg <fthre@OPTUSNET.COM.AU> wrote:
    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: Sext! ants 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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