Slit Image Test  
Overview  Computations  Setup  
Baldwin On SIT  Contact 
To download the SIT Conic spreadsheet click here (MD5 = F13AEAE7DF1F740BDC2250ADDC172D1C) Jeff Baldwin's youtube video  taking a SIT image Jeff Baldwin's youtube video  processing a SIT image click to download the 24 mega byte imageJ input tif file to be used with SIT spreadsheet Olympus E300 Evolt Canon T2i EOS Rebel 


SIT Nonlinear Algebraic Equations  
This is a newer and I think easier to understand version of the SIT equations. The original equations can be found here. And of course, both produce the same results. SIT is a Fixed Source Test and as such, the angle of the source ray s is equal to the angle of reflection ray r as measured with respect to the Normal per Fig1:
The Normal vector (per Fig1 equation 2) of the form y=mx+b is y=z'x+zz'+h, where zz'+h is the b term. Knowing z, the other side of that right triangle is found using similar triangles where the derivative z' serves as the other triangle with similar sides. Derivative z' and 1/z' are used in many places in Fig1 in this manner which has greatly simplified this new version of the SIT equations, which gets exactly the same results as the old. Excels Solver (Root finder) is used to find the numerical solution to the SIT nonlinear algebraic equations, which can be simply summarized as: z is varied (using a Root finder) until Yz of Fig2 equation 12 is nearly equals to Ym (the slit images as measured by ImageJ). Instead of using Z=Kz of Fig4 to compute the Foucault, Z=(hRz'+zz')/z' is used instead being it avoids multiplying by K=0 when the conic is a sphere. 


References

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2005  2020 Bill Thomas This work is licensed under a Creative Commons AttributionNonCommercialShareAlike 4.0 International License. 