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    Re: Comparison, Pan of Oil vs Mirror Artificial Horizon
    From: Bill B
    Date: 2015 Jun 23, 20:11 -0400

    A couple of questions:
    
    What method did you use to determine "overlap" when superimposing the
    images?
    
    Did you turn the micrometer drum in same direction for edge-to-edge
    observations? By that I mean NOT turning cw for one and ccw for the other.
    
    What do you believe your IE to be from superimposing vs. edge-to-edge?
    
    
    
    On 6/23/2015 7:31 PM, David Fleming wrote:
    > IC measurements	06/05/15							
    > 									
    > 	overlap			edge to	edge		difference	sum	
    > 1	3.2	on	on	32.6	28.3	off	4.3	60.9	
    > 2	3.5			31.6	28.6		3	60.2	
    > 3	4.2			32.2	29		3.2	61.2	
    > 4	3.3			32	29.3		2.7	61.3	
    > 5	3.9			32.6	29.1		3.5	61.7	
    > 6	3.2			32	28.6		3.4	60.6	
    > 7	4.1			32.4	29.1		3.3	61.5	
    > 8	3.8			32	29.4		2.6	61.4	
    > 9	3.1			31.8	30.1		1.7	61.9	
    > 10	3.5			32.1	29.2		2.9	61.3	
    > 11	3.4			32.5	28.9		3.6	61.4	
    > 									
    > avg	3.56			32.16	29.05		3.11	61.22	Sum/4
    > std	0.38			0.33	0.48		0.66	0.49	15.30
    > 									
    > 									
    > 							Semidiameter	15.8	
    >
    > Fred Hebard claimed that edge to edge sun index measuremets were more
    > accurate than overlapping measurements.  I don't believe the above data
    > supports that claim.
    >
    > Two sets of measurements were made on my Astra sextant with the 3.5
    > power scope.  First column is 11 overlapping measurements with about
    > 1/10 sun diameter side error which I believe is helpful for overlap
    > judgement but no proof for that.
    >
    > Then the side error was removed and I made 11 edge to edge measurements
    > (22 measurements in all).
    >
    > Precision in all sets of primary measurements are reasonably identical
    > order of .4 moa.
    >
    > But we see that the precision of the edge to edge values shows higher
    > spread, .66 moa.  Taking the difference of two numbers increases their
    > spread to square root two times the fundamental precision.  It is better
    > to utilize the time taking more measurements of one thing than two
    > things and taking their difference.
    >
    > Dave
    >
    > 
    > 
    >
    >
    
    

       
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