# NavList:

## A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

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Re: False Horizons
From: Nicolàs de Hilster
Date: 2007 Nov 20, 20:10 +0100

```Isonomia wrote in 3932:
> Eventually for my younger child  I tried setting up a plank in the
> garden and tying the sextant up with  string to give a level, but the
> darn sun moved so quick that it ran off the  end before I had a chance
> to set it up with any accuracy. I'd appreciate any ideas!
>

Then I proposed:
>> Perhaps making a simple quadrant would do for the kids and instead of
>> using two visors to look through you could make one with one small open
>> visor and a larger closed one to cast the smaller visor's shadow onto
>> the larger (so they do not have to look at the sun). After that exercise
>> you can explain that a sextant does a similar job using two mirrors.
>>
>>
Which resulted in Isonomia asking me:
> The principle sounds a good one for younger children and if the sun
> ever shines, I'll try out what I think you mean to see how accurate it
> is. But it would help if I understood what you meant by a "closed
> visor".
So I will try to explain here:

Normally a quadrant is used in a forward manner, like you can see on
image 'using a quadrant.jpg'. Facing the sun with the naked eye is not
really commendable, so my proposition was to use the quadrant backwards.
For this we need a quadrant with an open visor ('A' in the other image)
and a closed visor ('B').

For visor A you could take a screw eye, for B a piece of cardboard with
a cross drawn on it. Of course the line through the centre of the screw
eye and the intersection of the cross should be parallel with the

Accuracy depends on the diameter of the quadrant, but it is known that
approximately 16cm).

Nicolàs

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