IDL> fits_read, 'polar_90d_1s_19_redbias.fits', p1, header
IDL> fits_read, 'polar_90d_1s_20_redbias.fits', p2, header
IDL> fits_read, 'polar_90d_1s_21_redbias.fits', p3, header

IDL> shift_div_graph, p2, p1, pn, .95, 1.05, xrange=[0,1299], yrange=[0,1299], scale = .5
enter x shift: -.2
enter y shift: .3
Mean, Max, Min, StdDev
     0.997670      400.267     -211.161     0.478266

IDL> shift_div_graph, p3, p1, pn, .95, 1.05, xrange=[100,1299], yrange=[100,1299], scale = 1
enter x shift: .8
enter y shift: 1
Mean, Max, Min, StdDev
     0.997160      2.07355     0.443498    0.0358266

IDL> p2_f = shift_im_cbc(p2,-.2,.3)
IDL> p3_f = shift_im_cbc(p3,.8,1)
IDL> fits_write, 'polar_90d_1s_20_shifted.fits', p2_f
IDL> fits_write, 'polar_90d_1s_21_shifted.fits', p3_f

---------------------------------------------------------
IDL> fits_read, 'polar_90d_1s_19_redbias.fits', p90_0
IDL> fits_read, 'polar_45d_1s_20_shifted.fits', p90_1
IDL> fits_read, 'polar_45d_1s_21_shifted.fits', p90_2
IDL> p90 = (float(p90_0) + float(p90_1) + float(p90_2)) / 3.0
IDL> fits_write, 'polar_90d_1s_mean_aligned.fits', p90