# Montage Viewer: Overlays

The image can be overlayed with additional information such as coordinate grids and scaled symbols from a source catalog table. See the mViewer documentation sections on basic overlays and table overlays for more details.

    import astroMontage.mViewer as mv

    viewer = mv.mViewer()

    viewer.set_red_file("SDSS_r.fits")
    viewer.set_red_stretch("0.1s", "max", "gaussian-log")

    viewer.set_green_file("SDSS_g.fits")
    viewer.set_green_stretch("0.1s", "max", "gaussian-log")

    viewer.set_blue_file("SDSS_u.fits")
    viewer.set_blue_stretch("0.1s", "max", "gaussian-log")

    viewer.set_current_color("8080ff")
    viewer.add_grid("Equ J2000")

    viewer.set_current_color("90ff90")
    viewer.add_img_info("mipssed.tbl")

    viewer.set_current_color("ff9090")
    viewer.add_img_info("irspeakup.tbl")

    viewer.set_current_color("ffff00")
    viewer.set_current_symbol(1.0, "circle")
    viewer.add_catalog("fp_psc.tbl", "j_m", 16, "mag")

    viewer.set_current_color("ffffff")
    viewer.add_label(202.47083, 47.26614, "Messier 051b")

    viewer.set_current_color("000080")
    viewer.set_current_symbol(8.0, "circle")
    viewer.add_marker(202.49829, 47.26614)

    viewer.set_current_color("ffffff")
    viewer.add_label(202.41667, 47.21667, "Messier 051a")

    viewer.set_current_color("000080")
    viewer.set_current_symbol(12.0, "circle")
    viewer.add_marker(202.46963, 47.19517)

    viewer.init_browser_display()
In addition to the commands to add each type of overlay (all of which can have multiple instances) there are a couple of "sticky" command to set the color and symbol shape for any subsequent overlays until changed. Since we can't assume the user has access to a network at all times, we haven't opted for allowing object name resolution inside the methods here; all coordinates are in simple decimal degrees. Again, refer to the mViewer documentation for more details on things like color syntax, coordinates, and symbol shapes. | Click image to view full resolution in a new tab.