NavList:

Fine tuning and astigmatism.

At this point I am looking at variables that might shed some light on
previous trials.

First it was noted that side error can reduce 4SD observed.  That make
complete sense.  Given side error equal to the 2SD, the images would achieve
tangency at the same point both on and off the arc.  4SD = 0

Observing the effect of the my astigmatisms, I reported, "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."

I took a more critical look at that.  First I calculated the observed
diameter of the sun with a perfect eye and 3.5X scope 1d 50.6'.  Then I
measure the globes diameter from my usual spot.  55' diameter.  I then move
to a spot where the diameter of the globe viewed with the naked eye matched
the diameter of the sun so I am using the same parts of the eye.  Looking
critically, I noticed that the distortions were not symmetrical, around
either axis.  The long axis that comes closest to producing symmetry with
the left eye is rotated 10d clockwise from vertical, the long axis on the
right eye 8d clockwise from horizontal.  The distortions around the tilted
axis do not appear to be symmetrical.

The angles were measured with a clear plastic protractor held at arms
length, the hole centered on the globe above the support pole, and the
support pole aligned with base-reference mark.

The tilt of the distortions, like side error, may reduce the effect of the
distortions. That does not explain away the the 4SD undershoots, or the
shift of IE.

Bill


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