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George, GL and Peter,
Thank you all for continuing to offer helpful advice.  To answer some of 
George's questions about the horizon I am using, it is the inexpensivce Davis 
model, and has a sloped-roof type of cover, with solid plastic sides 
("gables" if you will) and clear or colored plastic panes.  The panes appear 
to be quite flat as far as one can tell by looking.  No doubt they are cut 
from large sheets after emerging from a pair of rollers set to a precise 
tolerance.  Perhaps in cooling or handling they acquire some irregularity.  
Moreover, the image is passing through the panes more or less normal to the 
surface.  It may be refracted a bit going through, but I don't think I'm 
seeing and extra reflection, as I might if I were reflecting the sun off a 
stack of horizontal plates.  Again, it may be reflecting from the top and 
bottom of the pan, so I will try some light-deadening measure on the bottom.

When I see the reflected sun in the pan of mineral oil, it is very distinct 
and solid, and depending on the cover I have over it, may be bright yellow.  
As I bring the sun down from the sky, again viewing through various filters, 
it will appear to the right of the yellow reflected image and will be, 
perhaps bright green or blue (depends on the filter).  There is no mistaking 
which is which, and no particular impression that either image is double.  
They will be separated horizontally anywhere from two to four or five 
diameters apart, but as I squirm and squint, fiddle with the telescope focus 
and the micrometer, and try to hold my toes just the right way, they drift 
slowly together, then apart again. It's much like watching the little 
floating debris on the surface of your eye; you can sort of chase it in one 
direction by eye-rolling or will power, but it always wants to slide back.  
But I digress.

I'll give your suggestions a try next time I'm out.  I'm especially grateful 
that some of you pointed out the advantage of getting the images edge-to-edge 
rather than totally coincident.  Let's see if this improves my results!

-John


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