The config file is divided into sections which start with a line like [body], where body is either default (everything in this section, which should be at the top, applies to all bodies unless overridden later), or a body name like saturn. Be careful to specify options that apply to only one planet under that planet's section, and not under [default]. For example, a common mistake is to put cloud_map=clouds.jpg under [default] and not under [earth]. Overlaying clouds on every planet is a huge waste of time! I won't explain the format of the config file beyond that; instead just look at the default supplied with xplanet. It should be straightforward. When making your own config file just modify a copy of the default config file. Each option is described below. The default values are the values used in the absence of a corresponding entry in the configuration file. arc_color Specify the default color for great arcs. This color will be overridden if a color is specified for an arc in the arc file. The color may be specified either as a name, a hexadecimal number, or as an RGB triple. For example, arc_color=red, arc_color=0xff0000, and arc_color={255,0,0} all mean the same thing. The default value is white. arc_file Specify a great arc file for this planet. This option may be used more than once. See the README and sample files in the xplanet/arcs directory for more information. The default is no arc files. arc_thickness Specify the default thickness for arcs. This also applies to the planet's orbit. This can be overridden in the arc file itself. bump_map Specify a bump map to use for relief shading. This is assumed to be an greyscale image file representing a digital elevation map with elevations ranging from 0 to 255. The default is no bump map. bump_scale Exaggerate the vertical relief for computing the shading. The default value is 1. cloud_gamma Apply a gamma correction to the cloud image before overlaying. Each pixel's brightness is adjusted according to: new_value = 255 * [(old_value/255)^(1/gamma)] The default is 1 (no gamma correction). cloud_map Specify an image to overlay on the planet map. The default is no cloud map. cloud_ssec If true, assume the cloud map is an image downloaded from the Space Science and Engineering Center (SSEC) at the University of Wisconsin. The latest image (updated every three hours) can be obtained from http://www.ssec.wisc.edu/data/comp/latest_moll.gif. This image is a 640x350 pixel Mollweide composite image with ugly pink coastlines. Xplanet will reproject and resize the image as well as remove and fill in the coastlines. cloud_threshold Cloud pixel values below threshold will be ignored. The value for threshold should be between 0 and 255. The default is 90. color If an image map for the body is not found, use the specified color instead. The default is white, although a color is specified for most bodies in the default configuration file. draw_orbit If true, draw the body's orbit about its primary. The default is false. See "orbit" below on how to describe how the orbit is drawn. The default is to not draw orbits. grid Draw a longitude/latitude grid. The spacing of major grid lines and dots between major grid lines can be controlled with the grid1 and grid2 options (see below). The default is false. grid1 Specify the spacing of grid lines. Grid lines are drawn with a 90/grid1 degree spacing. The default value for grid1 is 6, corresponding to 15 degrees between major grid lines. grid2 Specify the spacing of dots along grid lines. Grid dots are drawn with a 90/(grid1 x grid2) degree spacing. The default value for grid2 is 15; combined with the default grid1 value of 6, this corresponds to placing grid dots on a one degree spacing. image Specify the image map to use. The default is body.jpg (e.g. earth.jpg, neptune.jpg) magnify Draw the body as if its radius were magnified by the specified factor. This is useful for a lot of moons, as normally they would be drawn as dots compared to their primary. The default is 1 (no magnification). map Same as the image option above. mapbounds={lat1,lon1,lat2,lon2} Assume that each map file read in has its northwest corner at lat1,lon1 and its southeast corner at lat2,lon2. This is useful if you have a high-res map but just want to show a small area. marker_color Specify the default color for all markers. This color will be overridden if a color is specified for a marker in the marker file. The default is red. marker_file Specify a file containing user defined marker data to display on the map. This option may be used more than once. The default is no marker file. See the README and sample files in the xplanet/markers directory for more information. marker_font Specify the default font for all markers for this body. This option may be overridden inside the marker file. The default is to use the value from the command line -font option. marker_fontsize Specify the default font size for all markers for this body. This option may be overridden inside the marker file. The default is to use the value from the command line -fontsize option. max_radius_for_label Don't draw a label for the body if its radius is greater than this value. The default is 3 pixels. min_radius_for_label Don't draw a label for the body if its radius is less than this value. The default is 0.01 pixel. min_radius_for_markers Don't draw markers on the body if its radius is less than this value. The default is 40 pixels. night_map Use night_file as the night map image. If this option is not specified, a default night map will be used for the earth. If this file is not found, or for the other planets, the night map will be a copy of the day map, modified as described under the shade option. orbit Specify the start, end, and increment for the orbit. The units are orbital period and degrees. The default is {-0.5,0.5,2}. Remember to set "draw_orbit=true". orbit_color Specify the color for the orbit. The default is white. random_origin If false, don't use this body with -origin random, major, or system. The default is true. random_target If false, don't use this body with -target random or major. The default is true. satellite_file Specify a file containing a list of satellites to display. A file containing NORAD two line element (TLE) sets named satfile.tle must exist along with satfile. A good source of TLEs is www.celestrak.com. This option may be used more than once. The default is no satellite files. See the README and sample files in the xplanet/satellites directory for more information. shade If the night image file is not found, set the brightness of the night map to shade percent of the day map. If shade is 100, the day and night maps will be identical. The default value is 30. specular_map Use filename as a specular reflectance file. Normally it's just a greyscale image where the oceans are set to 255 and the land masses are set to 0. This is used to display the reflection of the sun off of the oceans. The default is no specular file. text_color Specify the color for the markers and body label. The default is red. twilight Let the day and night hemispheres blend into one another for pixels within the specified number of degrees of the terminator. The default value is 6.