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.
This command opens from the Process > Utilities menu.
Calculate Image Scale Properties
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Profile [|>] |
Selects the parameter profile for this command and allows you to save or work with existing presets. |
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[Select] |
Opens the Select Source Images dialog to choose images from an image window, folder, files, pattern, or a file list. |
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Load from Image |
The two values in this column may be taken from
keywords in the image header. To do so, specify the keyword and
click the |
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Focal Length |
Enter the focal length in units of mm or select a previous value from the list. Use the [+] and [x] buttons to add or delete the currently displayed entry. |
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Pixel Size |
Enter the pixel size in units of microns or select a previous value from the list.. Use the [+] and [x] buttons to add or delete the currently displayed entry. |
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(mm) |
Alternately, type in the focal length instead of taking it from an image header keyword. |
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(microns) |
Alternatively, type in the pixel size instead of taking it from an image header keyword. |
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Click this button to calculate the image scale from the specified quantities. |
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 andPixel
Size. After the values are entered into the two fields,
click 
(calculate) to compute the image
scale.
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 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.