Hi Kate,
There is still something wrong I am afraid. The RMS fit should be better than 1 Angstrom. For example I have just run a Balmer line calibration on one of my recent reference stars and get the following results (ALPY 600 2xbin 4.54um pixels, pixel size set to 8.97A (3123/348) )
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Wavelength fit deviation
point #1 x = 143.059 lambda = 3835.148 dlambda = 0.242
point #2 x = 154.045 lambda = 3888.984 dlambda = 0.066
point #3 x = 170.621 lambda = 3970.476 dlambda = -0.396
point #4 x = 197.253 lambda = 4101.992 dlambda = -0.242
point #5 x = 245.161 lambda = 4340.028 dlambda = 0.452
point #6 x = 349.413 lambda = 4861.473 dlambda = -0.133
point #7 x = 696.362 lambda = 6562.787 dlambda = 0.023
point #8 x = 762.564 lambda = 6872.013 dlambda = -0.013
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Coefficient a4 : 3.601046E-10
Coefficient a3 : -1.409022E-06
Coefficient a2 : 1.183699E-03
Coefficient a1 : 4.63613
Coefficient a0 : 3146.763
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RMS : 0.408720
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If you email me your spectrum image fits file, I can see if i can get a better result if you like
EDIT: typo in pixel size corrected (4.54 not 5.45)
Cheers
Robin