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I am still working to get my intercepts down to acceptable distance from a
known position on land or at anchor.  All too often I am about 2-4 miles
away. Perhaps my biologics are against me?  Even when I think that I have
perfectly lined up the sun's limb with a clear horizon, my sights tend to be
out by that much at times.  Perhaps I cannot see the limb and horizon as
clearly as my brain thinks it can.

For now, though, I would like to explore star image quality.  We have
discussed star sparkle before on this list, but I finally got around to
attempting to draw what I actually seem to see.  Sparkle makes it difficult
for me to precisely line up the star's images on top of each other. This
means that I have to take a series of sights to obtain an Index Error before
and after each round of sights, and then average them. Typically my
variation in a series of IE attempts ranges to about +/- 0.5' of arc, which
seems like a lot to me.  I would have thought that a navigator could expect
less variation, say +/ 0.2' or even 0.1'?

How do the images on the following page compare with what you see through
your sextant?  Is there more sparkle, or less?
http://jimthompson.net/boating/CelestialNav/CelestNotes/UsingSextant.htm



Jim Thompson
jim2@jimthompson.net
www.jimthompson.net
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