NavList:

Greg,

> Wonder if that might also account for the differencer
> between side error
> measured against the sun and that measured with Jupiter?

I also noticed that side error is sometimes different
when tested by Sun and when tested by stars on the same day.

The simplest explanation is that it actually changes
in few hours. Several people mentioned on this list
the strange property of SNO-T that the side error is
difficult to adjust, because the screw "plays back".
It indeed does this and my sextant does not hold this adjustment.
I thought that this is due to some fault in SNO design,
but now I have a second sextant, by Troughton and Simms
and it has exactly the same problem: it does not hold
the side error adjustment. I adjust it and it can go out
of adjustment in few minutes.

On the other hand, the theory (I refer to Chauvenet
where a formula is given) implies that the effect of
a moderate side error is negligeable.
So I rarely adjust it at all.
I also checked experimentally that there is no effect
of side error on my observations. I am talking of a side
error of 1-2 minutes.

Alex.


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