NavList:

George, you wrote:
"Those that are trying to  measure to a small fraction of a minute,
perhaps for lunars, will be most  conscious of the need to defend
against minute amounts of  backlash."

For what it's worth, even for lunars, I've never seen any  measurable
backlash in any sextant of reasonable quality.

I'll have to  dig up the reference on this, but it's interesting to note that
the earliest  references to backlash come from the 18th century --long before
the micrometer.  Supposedly because of possible differences in friction
between the index arm and  the arc, early quadrant users were told to make small
adjustments always in the  same direction.

-FER
42.0N 87.7W, or 41.4N  72.1W.
www.HistoricalAtlas.com/lunars 


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