NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
7/8 Scale Sextants Finale
From: Joel Jacobs
Date: 2004 Aug 2, 19:37 -0400
From: Joel Jacobs
Date: 2004 Aug 2, 19:37 -0400
We're pretty far off the topic of navigation except
as it relates to the effect of scaling down a sextant.
What Robert Gainer and George Huxtable are talking
about are what in some books are called the laws of relativity and
similitude.
In simple form, these laws say that if you double
anything, evenly all around, you will increase its surface area by 4 times, and
its volume by 8 times. Even more impressive, in respect to a vessel, you'll
increase stability 16 times. The same thing happens in reverse, so if you make a
boat half the original size, it will weight 8 times less and be 16 times less
stable.
With those figures in mind, you can visualize how a
small reduction in the size of a sextant can have on its performance under low
light, high altitude or rough seas.
Since I don't have any SNO-T sextants for sale, I
can't be accused of being self-serving when I point out again that they are
smaller than normal by about 12%, lighter, and have large sized mirrors.
With the right scope you have a good package at an economical
price.
The ASTRA sextant which I do have for sale falls
into that same category, and has worldwide service and parts availability, and
should be included in any serious evaluation of which sextant to
buy.
Joel Jacobs
