Given: pixel = (nc - 1) - column    
For echelle order 7: pixel = (nc/2 - 1) - column

wavelength = coef[0] + pixel*coef[1] + (pixel^2)*coef[2] + (pixel^3)*coef[3]

Echelle order 3:
tsns_coef[0]= 1.8755909e+04
tsns_coef[1]= 2.8994934e+00
tsns_coef[2]=-8.6287104e-06
tsns_coef[3]=-8.0330325e-10
NOTE: sky line wavelength fit: tso=3 N= 27  disp=2.877(2.854-2.899)A/px  
      high=0.744(px) wrms=0.251(px) wppd=0.314(px)

Echelle order 4:
tsns_coef[0]= 1.4097953e+04
tsns_coef[1]= 2.1746359e+00
tsns_coef[2]= 3.1289207e-07
tsns_coef[3]=-4.4578053e-09
NOTE: sky line wavelength fit: tso=4 N= 55  disp=2.147(2.120-2.175)A/px  
      high=0.479(px) wrms=0.121(px) wppd=0.259(px)

Echelle order 5:
tsns_coef[0]= 1.1296277e+04
tsns_coef[1]= 1.7444930e+00
tsns_coef[2]=-1.5133149e-06
tsns_coef[3]=-3.3566630e-09
NOTE: sky line wavelength fit: tso=5 N= 53  disp=1.720(1.696-1.744)A/px  
      high=1.229(px) wrms=0.310(px) wppd=0.427(px)

Echelle order 6:
tsns_coef[0]= 9.4285198e+03
tsns_coef[1]= 1.4518298e+00
tsns_coef[2]= 4.0252735e-06
tsns_coef[3]=-4.4555188e-09
NOTE: sky line wavelength fit: tso=6 N= 57  disp=1.433(1.413-1.453)A/px  
      high=0.893(px) wrms=0.266(px) wppd=0.420(px)

Echelle order 7:
tsns_coef[0]= 9.3841196e+03
tsns_coef[1]= 1.1731967e+00
tsns_coef[2]= 9.8239646e-05
tsns_coef[3]=-5.7946139e-08
NOTE: sky line wavelength fit: tso=7 N= 18  disp=1.201(1.173-1.229)A/px  
      high=-0.700(px) wrms=0.278(px) wppd=0.499(px)