Robin et al,
Thought I’d better make it clear that in my original post with the coefficients, I put in copy the lower set that is reported in the log file. . There is an upper set reported call the “primary dispersion” which I couldn’t relate to my pixel data, but guessed it was some master set in ISIS covering 11 different wavelengths, amended by my data in some way to allow setting of the research pixel windows of +/-7. I’m copying this set below anyway, just in case it’s relevant.
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Primary dispersion :
Coefficient a4 : -2.657745E-13
Coefficient a3 : 7.117650E-09
Coefficient a2 : -6.547758E-05
Coefficient a1 : 0.53625
Coefficient a0 : -971.891
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RMS : 0.125248 (en pixels)
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Primary wavelength fit deviation
point #1 Lambda = 3770.630 px = 447.009 dx = -0.091
point #2 Lambda = 3797.300 px = 454.713 dx = 0.211
point #3 Lambda = 3835.390 px = 465.697 dx = -0.107
point #4 Lambda = 3889.050 px = 481.138 dx = -0.018
point #5 Lambda = 3970.080 px = 504.383 dx = 0.059
point #6 Lambda = 4101.750 px = 541.995 dx = -0.068
point #7 Lambda = 4340.480 px = 609.798 dx = -0.023
point #8 Lambda = 4861.340 px = 756.864 dx = 0.054
point #9 Lambda = 6562.850 px = 1246.125 dx = -0.096
point #10 Lambda = 6869.000 px = 1337.306 dx = 0.092
point #11 Lambda = 7605.000 px = 1560.933 dx = -0.012
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BTW, if I calculate the RMS for the dx above I get 0.09241 and not 0.125248 [maybe it is weighted in some way not disclosed]. The same is true for the dlambda figures noted in my earlier post.
john