In May 2015, MC did engineering to map the POM value for various RA, DEC position. The values currently used by smokey likely date back to 2000-ish. Here is MC's engineering report: EngineeringReport160518.pdf For the XYStage and POM, smokey used a Rotation, Scale, Translation maxtix based on 2D graphic principles. However, this was a complex solution just to fit motor postions to Arcseconds offset, plus it is difficult to update, and maintain. So the 1606 version of smokey swap out the translation matix for polynomial equations. This page documents the converts of the current R,S,T matix to polynomial coefficients. And coefficient on the Engineering report are shown, and reverse coefficients are produced. POM matix coeff - convert Rx,Sc,Tx to 2d coefficients. Using the old mm2as_m, and as2mm_m (t2d_matrix), I produced points show the mm to AS value for the POM X and Y axis. The values came from the ic's do_xp() command. pom_x_matix.txt pom_y_matix.txt #define POM_X_POLY_DEG 2 // 2nd degree polynomial double Pom_x_mm2as[POM_X_POLY_DEG] = { 7017.4812, -611.33032, -0.00015493176 }; double Pom_x_as2mm[POM_X_POLY_DEG] = { 11.479000, -0.0016357674, -6.7806209e-13 }; #define POM_Y_POLY_DEG 2 // 2nd degree polynomial double Pom_y_mm2as[POM_Y_POLY_DEG] = { 8074.5882, -749.59353, 0.00028655344 }; double Pom_y_as2mm[POM_Y_POLY_DEG] = { 10.772000, -0.0013340673, 6.8014315e-13 }; Ref: runfit.pro for IDL code product values. STAGE matix coeff - convert Rx,Sc,Tx to 2d coefficients. Using the old step2as_m, and as2step_m (t2d_matrix), I produced points to show the Steps to AS value for the X and Y Stages. The values came from the ic's do_xs() command. xstage_matrix.txt ystage_matrix.txt #define XYSTAGE_POLY_DEG 2 // 2nd degree polynomial double Xstage_step2as[XYSTAGE_POLY_DEG] = { 2.5701250, 0.0051400000, -2.7216227e-13 }; double Xstage_as2step[XYSTAGE_POLY_DEG] = { -500.02430, 194.55252, 2.0042329e-06 }; double Ystage_step2as[XYSTAGE_POLY_DEG] = { -21.760068, 0.0054399974, 1.3528666e-13 }; double Ystage_as2step[XYSTAGE_POLY_DEG] = { 4000.0139, 183.82358, -8.4035830e-07 }; Ref: runfit.pro for IDL code product values. NEW POM and XYStage coefficients The program reverse_equ.pro was used to create the reverse fits for the new coefficient provide in the EngineeringReport160518.pdf. POM X EngReport provide this xrange of -300 to 300 AS: double Pom_x_as2mm[POM_X_POLY_DEG] // X AS->mm #if MAIN = { 11.538800, -0.0020264400, 0.00000 }; // 2016-06: from EngineeringReport160518 #endif ; reverse_equ.pro: double Pom_x_mm2as[POM_X_POLY_DEG] // X mm->AS #if MAIN = { 5694.1319, -493.47773, 6.8650618e-05 }; // 2016-06: from EngineeringReport160518 #endif ; POM Y EngReport provide this xrange of -300 to 300 AS: double Pom_y_as2mm[POM_X_POLY_DEG] // Y as->mm #if MAIN = { 10.8834, -0.00120011, 0.00000 }; // 2016-06: from EngineeringReport160518 #endif ; reverse_equ.pro: double Pom_y_mm2as[POM_X_POLY_DEG] // Y mm->AS #if MAIN = { 9068.6868, -833.26033, 0.00015670671 }; // 2016-06: from EngineeringReport160518 #endif ;