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    Re: Bubble sextant trials
    From: Robert Eno
    Date: 2007 Feb 14, 14:03 -0500

    Alex wrote:
    > Further remarks. The averager seems useless for observations from
    > a stable platform. Besides, it is very heavy, and my hands get tired
    > in the two minutes needed for an observation. So Ken's idea to cut
    > the averager off seems reasonable for backyard observations.
    Eno comments:
    The averager is of no use for land-based obserations and in fact using it will 
    lessen the accuracy of your shots. There is simply no practical value to 
    using the averager.
    Alex wrote
    > I wonder if the averager will help on a small boat.
    Eno comments:
    Doubtful. Bubble sextant observations at sea are at best, a crap shoot; at 
    worst, useless; unless you are taking observations on a flat-calm sea. The 
    averager was designed for the relatively stable platform of large aircaft and 
    not pitching, yawing vessels at sea. I suppose in a pinch, bubble sextant 
    observations at sea would be better than no observations at all but one would 
    have to draw a 20 mile circle of error around the resultant position.
    Alex wrote:
    > I noticed that something strange happens with the bubble:
    > as I observe, small bubbles come from 10 oclock direction and
    > join my main bubble. So it grows:-)
    > Do I have to rotate the bubble wheel anticlockwise (relaxing the
    > tension
    > of the membrane) after the size of the bubble is adjusted?
    Eno comments:
    Yes. Once you have formed the bubble to the desired size, you must back off 
    the tension on the bubble adjustment wheel. This is especially so with the 
    C.Plath SOLD design. In very cold weather, you will notice that the bubble 
    gets larger and has to be adjusted to compensate for this.
    Alex wrote:
    > Will try some stars if weather permits.
    Eno comments:
    And this my friend, will be the point at which you will appreciate the beauty 
    of the bubble chamber illumination system of the MK IX series and why it is 
    far superior to other bubble illumination systems.
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