Calculate Image Scale


The Calculate Image Scale command is a utility command that calculates the number of arcseconds per pixel for angular projections onto the image.

The image scale in units of arcseconds per pixel is labeled arcsec / pixel in the dialog. To compute this value, Mira uses the focal length in units of millimeters (mm) and the image pixel size length in units of microns. These values can be obtained from two sources: From you or from the image itself using header keywords for the Focal Length and Pixel Size. After the values are entered into the two fields, click (calculate) to compute the image scale.

Obtaining Input Values from the Image

The Focal Length and Pixel Size are often stored in the image using header keywords. To load these values from the image, use the two History Combo Boxes on the left side of the dialog. These boxes remember previously entered values which can be recalled, or you can type new keyword names into the fields. When the keyword(s) are visible in the combo box field(s), click to load the value(s) from the image header. To compute the image scale, click the button.

Related Topics

Set Arcsecond Scale