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Fred wrote:

> Fourth, the 4x telescope for my C+P shows changes in side error
> depending upon the focus setting.  Is anything like that happening
> with yours? (I don't know this would affect the sights.

Thank you for posting that, I was wondering why the side error on my
Astra seemed to vary between a terestrial sight and a celestial one -
you may have nailed it.

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

--
GregR

--- Fred Hebard  wrote:

>
> Bill,
>
> Some dumb suggestions, in no particular order of priority.
>
> First, you mentioned you add a slight side error to improve star IC
> checks.  Have you tried nulling that out?
>
> Second, have you had others try an IC check on the sun with your
> sextant and compared to yours?
>
> Third, have you tried changing the position of tangency to try to at
>
> least get the SDs to agree?
>
> Fourth, the 4x telescope for my C+P shows changes in side error
> depending upon the focus setting.  Is anything like that happening
> with yours? (I don't know this would affect the sights.
>
> Fred
>
> On Jul 10, 2006, at 5:47 PM, Bill wrote:
>
> >
> > After a long series of tests, I have determined I have a problem,
> > and don't
> > know how to adjust for it.  I feel like I am overlooking something
>
> > obvious,
> > but just can't get a handle on it.
> >
> > My left eye distorts a sphere, with the vertical axis longer than
> the
> > horizontal axis.  My right eye distorts a sphere with the vertical
>
> > axis
> > shorter than the horizontal axis.
> >
> > When doing IE checks with my left eye (which I use for observations
>
> > although
> > being right-eye dominant as the left eye is sharper for some
> > reason) and two
> > sun images my vertical and horizontal sextant positions yield two
> > different
> > sets of results. (Before suggesting frame rigidity, I can reverse
> > the effect
> > using the right eye.)
> >
> > Sun Hc nominally 63d, left eye
> >
> > Vertical average on the arc:             32!08'
> > Standard deviation:                       0!10'
> > Vertical average off the arc:    29!17 = 30!83'
> > Standard deviation:                       0!10'
> > 4 SD from Almanac:                       63!2'
> > 4 SD observed:                           62!9'
> > IE:                                       0!625' on the arc
> >
> > Horizontal average on the arc:            31!65'
> > Standard deviation:                       0!1'
> > Horizontal average off the arc:  28!75 = 31!25'
> > Standard deviation:                       0!10'
> > 4 SD from Almanac:                       63!2'
> > 4 SD observed:                           62!9'
> > IE:                                       0!20' on the arc
> >
> > Vertical minus horizontal on the arc:     0!43'
> > Vertical minus horizontal off the arc:   -0!42'
> >
> > If I achieve tangency with the left eye and rotate the sextant
> > (handle up or
> > down) the images will separate.  If I achieve tangency with the
> > right eye
> > and rotate the sextant (handle up or down) the images will overlap.
>
> > Again, I
> > don't think I can blame frame rigidity for the discrepancy.
> >
> > Later tests done with sun Hc nominally 32d, left eye
> >
> > Vertical average on the arc:             31!625'
> > Standard deviation:                       0!08'
> > Vertical average off the arc:   29!595 = 30!405'
> > Standard deviation:                       0!10'
> > 4 SD from Almanac:                       63!2'
> > 4 SD observed:                           62!03'
> > IE:                                       0!11' on the arc
> >
> > Horizontal average on the arc:            31!875'
> > Standard deviation:                       0!10'
> > Horizontal average off the arc:  28!90 = 31!10'
> > Standard deviation:                       0!11'
> > 4 SD from Almanac:                       63!2'
> > 4 SD observed:                           62!975'
> > IE:                                       0!39' on the arc
> >
> > Vertical minus horizontal on the arc:     0!25'
> > Vertical minus horizontal off the arc:   -0!305'
> >
> > NOTE:  All sun IE checks were made without changing focus, as this
>
> > will
> > change IE and side error with my scope.
> >
> > It makes some sense to me that as the sun begins to squish
> > marginally, the
> > images appear closer to a sphere to my left eye, so vertical and
> > horizontal
> > observations become closer.
> >
> > Using a natural horizon, flat-roof buildings, radio towers and tree
>
> > lines 3+
> > miles away across the Wabash River valley I am observing -0!1 IE
> > (off the
> > arc) +/- 0!1 minute (no filters).  So this whole thing is driving
> > me up the
> > wall. My clusters are tight.
> >
> > Are there some other tests the list might propose?
> >
> > More to the point, is there some way to mathematically null out the
>
> > eyeball
> > problem and possible problems with shades (shades on sun but often
>
> > not on
> > the horizon) factor when using a sphere (sun or moon) and a natural
>
> > (flat
> > line) horizon with my left eye?
> >
> > Along the same line, if I am deriving distance from the top of an
> > object
> > with its base below the water line (Bowditch table 15), should I
> > regard the
> > top of the object as a point source, or is my vision causing the
> > object to
> > appear taller, hence I am observing too large an angle between the
>
> > top and
> > horizon?  The question being, will that cause me to observe a
> > larger angle
> > therefore calculate my distance closer to the object; so I need to
>
> > derive my
> > own "constants" for Bowditch T15 etc. for my eyes?
> >
> > As a check, I ran a series of tests using shoreline objects of
> > known height
> > whose bases were visible, and I always overshoot the angle needed
> > to make
> > the trig work.
> >
> > Any thoughts would be appreciated.
> >
> > Bill
> >
> >
> > >
>
>
> >
>


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