PISCES FIELD DISTORTION.

It has been compute a solution for the geometric distorsion of the images from the Pisces IR imager. The coefficients of the polynomials have been calibrated using a laser cut sieve mask. Such polynomials obtain a 0.6-pixel accuracy in one sigma error, which is sufficient for the MultiDrizzle PyRAF task to combine mosaics of exposures, to reject cosmic rays artifacts, and to co-add dithered images. Attached below is the distortion field image before/after drizzle processing and the analysis. The cubic file can be download from the link: https://wiki.lbto.org/pub/AdaptiveOptics/PiscesDistorsion/pisces.cubic . Also it is attached a brief distorsion field document.

Fitted Drizzle coefficients for the following polynomials are given below.

x'=a0+a1(x-x0)+a3(x-x0)^2+a6(x-x0)^3+a2(y-y0)+a5(x-x0)(y-y0)+a7(x-x0)^2(y-y0)+a5(y-y0)^2+a8(x-x0)(y-y0)^2+a9(y-y0)^3

y'=b0+b1(x-x0)+b3(x-x0)^2+b6(x-x0)^3+b2(y-y0)+b5(x-x0)(y-y0)+b7(x-x0)^2(y-y0)+b5(y-y0)^2+b8(x-x0)(y-y0)^2+b9(y-y0)^3

a0 =0.31287813289037253, a1 = 0.9989828135865076, a2 = 6.8474289493308e-4, a3 = 4.39629200796965e-6, a4 =-4.26610488387903e-6,

a5 =1.17300995566922e-6, a6 = -5.777022607025818e-8, a7 =-2.121349496671524e-9, a8 =-6.117022664638264e-8, a9 =7.321516204577285e-10.

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b0 =-0.0100861093583247, b1 = 6.115604237933e-4, b2 =1.0010171864134925, b3 =-6.931193084752701e-7, b4 =3.707140290113067e-6,

b5 =-6.02687131323977e-6, b6 =-4.858679562493253e-10, b7 =-6.435863352878359e-8, b8 =-1.412857789742458e-9, b9 =-5.79599337853739e-8.

• Raw sieve-mask images (violet) and Drizzle corrected (blue). Raw data shows pin-cushion distortion with peak value of about 20 pixels:
  

• Drizzle_coefficients_for_PISCES.pdf: Drizzle coefficients analysis for PISCES

• pisces.cubic: Cubic