Set Independent Linear Scales

The Set Independent Linear Axis Scales command attaches independent linear coordinate systems to the X and Y axes of the image. To set the same scale for both axes, you can also use the Set Linear Scale command. Keywords that define a world coordinate calibration are inserted into the image header by this command.

The Set Independent Linear Scales command opens from the Image Window > Coordinates menu and button on the Main Toolbar. The "immediate" form, shown first, opens when an image or image set is displayed in the top-most window. The general form can be used to select source images from folders, windows, or by matching templates.

Set Independent Linear Scales Properties
Profile [\|>]	Selects the parameter profile for this command and allows you to save or work with existing presets.
[Select]	Opens the Select Source Images dialog to choose images from an image window, folder, files, pattern, or a file list.
X Axis Scale	Enter the X axis scale in linear units per pixel.
Coordinate Unit	Specify the units to be attached to the X axis coordinate system. Use the [+] and [x] buttons to add or delete the currently displayed entry.
X Axis Scale	Enter the Y axis scale in linear units per pixel.
Coordinate Unit	Specify the units to be attached to the Y axis coordinate system. Use the [+] and [x] buttons to add or delete the currently displayed entry.
Set world coordinates at pixel coordinates	Check this box to enter a coordinate value at a pixel location. If checked, the properties below are enabled and must be specified. If not checked, the coordinate scale begins with world coordinate (0,0) at pixel position (1,1).
Pixel Coordinates at	In this section, select the method for entering the Pixel Coordinates fields from the bullet list.
Entered Coordinates	Accepts the pixel coordinates you enter into the Pixel Coordinates fields.
Cursor Position	Accepts the location of theImage Cursor as the pixel coordinates. Entries in the Pixel Coordinates fields are ignored.
Cursor Centroid	Calculates the centroid position near the Image Cursor to get the pixel coordinates. Entries in the Pixel Coordinates fields are ignored.
World Coordinates	Enter the X and Y world coordinates corresponding to the pixel coordinate values.
Pixel Coordinates	Enter the pixel coordinate values when selecting the Entered Coordinates bullet option.

This command applies a World Coordinate System ("WCS") calibration to the image or image set. This calibration replaces any existing WCS. However, this command creates an Undo copy so that you can use the Edit > Undo (Ctrl+Z) command to restore the previous coordinate system. To save the calibration permanently, save the image in the normal way. The screenshot below shows a FITS Header Pane with coordinate system keywords added to the image header by this command. In this example, the same scale was applied to both the X and Y axes.

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