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> I should have said the glass for the horizon mirror is not
> half-silvered.  There is no glass on the horizon, non-silvered side,
> just air.  I suppose one would still call this a split-horizon mirror,
> as opposed to a whole horizon mirror.

Fred

Interesting.  My cardboard unit is similar. Front silvered horizon and index
mirrors, or more accurately polished stainless steel.  No refraction
problems from the glass, so just air on the left side of the horizon
"mirror."  No optics, so no "overlap" in the middle or faint image on the
left side.

The biggest challenge is that both the index and horizon "mirrors" are
identical in size.  Therefore the index mirror cannot cover the entire
horizon mirror, so there is a gap between the horizon side and the body in
the mirror half, unless one puts in ton of side error.  Initial
"calibration" is achieved by rotating the index arm until its mirror edge
appears as a slit in the horizon mirror, and then putting a marker line on
the horizon mirror at the "slit."

In use, one aligns the marker line to the horizon, and the body to the
marker line.  Not easy on boat, but doable and more accurate than one might
expect.

Is the index mirror on the Davis large enough to cover the horizon mirror,
so one might do IE checks with a star?

Bill

   

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