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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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