Hello, I am trying to use the new IDL graphics, but am struggling with a couple aspects. I have two questions: 1. How can you overplot a single contour that has a value of ZERO? If I set c_value=0, that tells CONTOUR to use N_LEVELS. I can generate the filled contour plot just fine, but I like to overplot the zero line. 2. How can you change the number of major ticknames for the COLORBAR function? I would like to compose a figure that has e.q. 21 filled contours, but a discrete color bar that has a tick interval of e.g. 4. I have tried applying many of the properties, but none work! Here is an example: ;TESTING*** ; Make Discrete Color Levels ct_number = 39 nlevels=21 fdata=findgen(256,80)/(256*80)-0.5 levels=(findgen(nlevels)-(nlevels-1)/2.)*max(fdata)/(nlevels-1)*2. ct_indices = BYTSCL(levels) LOADCT, ct_number, RGB_TABLE=ct, /SILENT step_ct = CONGRID(ct[ct_indices, *], 256, 3) c1 = CONTOUR(fdata, $ indgen(256),indgen(80), $ c_value = levels, $ RGB_TABLE = step_ct, $ RGB_INDICES = ct_indices, $ /FILL, /buffer, xstyle=1,ystyle=1, $ MARGIN = [0.15, 0.20, 0.15, 0.15], $ TITLE = 'TESTING') c2 = CONTOUR(fdata, $ indgen(256),indgen(80), $ c_value = 0, c_color=0, n_levels=1, c_label_show=0,$ xstyle=1,ystyle=1,overplot=1) cb = COLORBAR( $ TARGET = c1, $ TICKLEN = 0, $ MAJOR = 5, $ FONT_SIZE = 10, $ BORDER=1, $ POSITION = [0.2, 0.07, 0.8, 0.1]) c1.save, 'testing.png' Any help would be much appreciated! Thank you, Rob