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Norm,
It is not the vital part, I agree, as long as the non-adjustable
telescope points right (to the dividing line on the horizon glass).
However, this is a very useful part, especially for fine measurement
of index error, and some other precise measurements.
It permits you to adjust
the relative brightness of the two images much more exactly than you
can do using filters.
This is important when you do IC with horizon, with Sun or Moon, star
distances, and I suppose, Lunar distances.

Modern sextants do not have this feature.

Alex.

On Tue, 10 Dec 2013, Norm Goldblatt wrote:

>
> School me, oh wise ones.  The telescope adjustments are not very critical, 
are they? As long as it's roughly centered on the horizon mirror, Seems as 
though, perish the thought, a threaded bolt and two locknuts for height and  
a twist for horiz. and a little non-elastic bending of 'rising piece' bolt 
would do 'er and actually be pretty solid. The rising piece on my T&S has a 
bit of play which I can't see how to get rid of, the two #3? screws that 
adjust vertical (perp to plane of sextant) are quite 'dinky' and given the 
torque that could be accidentally applied to the longest of my telescopes 
could damage them.
>
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