Hi Phil, Coming in a second email is a 252 Meg file containing the model grid. The first line of the file contains two numbers: first is number of points of each line of sight, second is number of plane-of-sky points. The remaining lines were made in a nested do loop, with the inner loop looping through the line of sight points and the outer loop looping over the plane-of-sky locations. Each of these lines contains: r, theta, phi, density, temperature, B_r, B_theta, B_phi, velocity (scalar). openw,lun,'OBSERVABLES/COMP/compcube.dat',/f77_unformatted,/get_lun writeu,lun,LosPramsStruct.Nlos,nunwrap for j = 0,nunwrap-1 do begin for i = 0,LosPramsStruct.NLos-1 do begin writeu,lun,r3D(i,j),theta3D(i,j),phi3D(i,j),ModSolStruct.Dens(i,j),ModSolStruct.Temp(i,j),$ ModSolStruct.Br(i,j),ModSolStruct.Bth(i,j),ModSolStruct.Bph(i,j),ModSolStruct.Vel(i,j) endfor endfor free_lun,lun James Dove, Ph.D Dept. of Physics, MSCD (303)556-2667