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#### A.5.3.2 Aux Axis

The Aux Axis control () is only visible when the Aux colour mode has been selected for one of the data layers. It controls a single colour scale for points which are coloured by data value to represent an additional dimension in the data.

This control has three following tabs.

Aux axis control Map tab

The Map tab controls the aux axis colour map. It has the following options:

Shader
  Select the colour map from a list of options.
Shade Log
  Whether the aux scale should map linearly or logarithmically into the colour map.
Shade Flip
  Whether the aux scale should map forwards or backwards into the colour map.
Null Colour
  What colour should be used to represent points with a null value for the aux data coordinate. If the associated Hide option is selected, then those points will not appear in the plot at all.

Aux axis control Ramp tab

The Ramp tab controls the display and annotation of the colour ramp that displays the colour map on the plot. It has the following options:

Show Scale
  Whether the aux scale ramp is visible; if so an appropriately labelled colour ramp appears at the right of the plot. The associated Auto option makes this decision automatically: if any aux data is plotted, the scale will appear, otherwise it won't. Deselect Auto if you want to determine visibility by hand.
Aux Axis Label
  Selects the axis label to be displayed near the aux colour ramp if it is visible. The associated Auto option, if selected, uses the name of one of the coordinates supplying aux data; deselect Auto if you want to enter a label by hand.

Aux axis control Range tab

The Range tab lets you enter lower and upper values for the aux data range by hand, and provides a double slider to restrict the range within these limits. If either the lower or upper range is left blank, it will be determined from the data.

Note the font used for labelling the aux axis is currently controlled by the font from the Axes selector.

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TOPCAT - Tool for OPerations on Catalogues And Tables
Starlink User Note253
TOPCAT web page: http://www.starlink.ac.uk/topcat/
Author email: m.b.taylor@bristol.ac.uk
Mailing list: topcat-user@bristol.ac.uk