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    Re: Instrumental errors
    From: Greg Rudzinski
    Date: 2015 Jun 26, 13:12 -0700

    David,

    You may have flipped the off arc columns. The sums of each set should be less than 62' if S.D. is 15.77'. 

    I recommend using solar film over the scope objective lense. Focus for a sharp limb and well defined sunspots. Try for matching dim Sun images if using sextant shades. I use both limb to limb and overlapping methods and get identical results. Limb to limb is preferred on a high Sun. Overlap preferred on a low Sun. Spead should be something less than 0.5' on sets of ten.

    Greg Rudzinski

    From: David Fleming
    Date: 2015 Jun 26, 10:17 -0700

    To: Bill Morris, BillB, and Fred Hebard

    I hope you all see this response in this new daughter thread, the topic was fish out of water in the previous.

    Thanks to you all for helping me proceed with evaluating efficacy of IC measurement schemes and the inspiration of your work that you related to me.

    I am going to repost my original data with errors of analysis, as pointed out by Bill B corrected and more extensive statistical analysis that is I think not too far from the truth.

    To me the bottom line baring mistakes is, as I originally maintained, overlap is supperior in measuring IC compared to edge to edge.

     
            
     
     
    IC measurements 06/05/2015        
       onoff     
    #overlap,on edge toedge60-off    
    13.2 32.628.331.7 edge to edgeerror propagation
    23.5 31.628.631.4    
    34.2 32.22931 std IC^2 =0.015  
    43.3 3229.330.7std IC=0.124  
    53.9 32.629.130.9    
    63.2 3228.631.4    
    74.1 32.429.130.9    
    83.8 3229.430.6    
    93.1 31.830.129.9    
    103.5 32.129.230.8    
    113.4 32.528.931.1    
          ICsum  
          (On-60Off)/2On+60Off  
    avg3.56 32.16 30.950.6163.11  
    std0.38 0.33 0.48    
    range1.1 1 1.8    
    mean std(11)0.115 0.099 0.145 SemidiameterSum/4 
    mean std(22)0.079    NA15.815.78 
          per BillB/Frank15.77  
                                 

     

     

     

     

     

     

     

    This data compares overlap measurement of IC to edge to edge measurement. All numbers are moa.

    The overlap method resulted in an average IC of 3.56 from a .38 stdDev(n-1) population.  The stdDev of the mean( 1/sqrt(11) smaller is .115.  So the IC measured was 3.56 +/_ .115.  Had I taken 22 measurements which was the effort used in the edge to edge case the error would have been +/- .079.

    The edge to edge data gives an IC = .61 +/- .124.   .61 = (32.16 - 30.95)/2    +/- .124 follows from the following analysis.

    Error of on edge mean .099, as in overlap calculation, and edge off error .145.   IC given by = .5(avg on + avg off).  Error propagation:

    SD^2 = ( .5 SDon^2  + .5 SDoff^2 )   so .124=sqrt(sq(.5*.099) +sq(.5*.145)).

       
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