Create Master Bias

The Create Master Bias command combines raw bias frames to create a Master Bias frame having higher signal to noise ratio than any of the raw frames. This command also allows a bias correction to be applied to the raw bias frames before creating the new master bias. The utility of this feature is for creating a master bias that reflects only part of the bias correction, for example, to evaluate changes to the bias pattern or structure in comparison with a baseline bias frame.

The Create Master Bias command opens from the Image Window > Process > Calibration 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.

Create Master Bias Properties

Profile [\|>]	Manages the parameter collection used by this dialog. See Profile Control for details.
Select	Opens the Select Source Images dialog for selecting source images to be processed into the final calibrated result. The name of the first selected file or displayed image is listed in the field to the right.
Name of Master Bias to be created	Enter a name for the Master Bias being created or click [...] to browse and choose a name from existing images.
Create in subfolder:	Enter the name of the subfolder where the Master Bias will be created. This is a subfolder of the folder containing the first raw bias frame in the source image list.
Overwrite existing files	Check this box to overwrite an existing file having the same file name in the output subfolder. If this box is not checked and a file of the same name exists, an underscore and number will be appended to the output file. For example, if MasterBias.fts exists and this box is not checked, then the output file will be named MasterBias_2.fts
Combining Strategy...	Click this button to set properties for combining the Bias frames.
Bias Correction...	Click this button to open the Bias Correction Properties dialog for applying an existing bias correction to the raw bias frames. For example, you may wish to compute a "pattern bias" frame from raw bias frames by subtracting an existing master bias.
Display result	Check this box to display the resulting Master Bias.
Log Processing	Check this box to list verbose processing messages in a Text Editor window. If the window already exists from previous processing by this or another calibration command, then its contents are appended.
Log processing to:	The drop list provides options for listing messages: -- None -- lists no processing messages Messages lists processing messages in the "Calibration Message Log" text area at the bottom of the dialog. Text Editor lists processing messages in a Text Editor window named "Calibration Message Log".
Notification:	Select the type of notification Mira issue when processing is finished: Do nothing quietly ends the processing without notification. Beep creates a notification sound, Message displays a notification message in a top level dialog that locks out Mira use until you dismiss the message.

Combining Strategy

The [Combining Strategy...] button opens the Image Combining Properties dialog for configuring how pixel values are combined in the final processing step, after bias and dark corrections are applied to the raw flat frames. For a description of the properties set in this dialog, see the Statistical Estimators for Image Combining and Region Statistics topics.

Image Combining Properties
Combining Method	This list box selects the type of processing used to combine the image values. These are described in Statistical Estimators for Image Combining. If the combining method takes Properties, these are presented in 1 or 2 fields to the right of the Method selection box. Some methods have no Properties, so no fields are visible. For example, in the picture above, the Mean - Alpha Clipped method uses 2 Properties: the number of highest--value pixels to clip ("High count") and the number of lowest-value pixels to clip ("Low count").
[Normalization Statistic]	Click this button to open the Region Statistics dialog for selecting normalization properties.
Target Pixel Type	Select a Pixel Type for the output image that can accommodate the increased signal and dynamic range of the combined images. For example, if combining a large number of 16-bit integer type images it is usually prudent to set the Pixel Type of the output image to 32-bit real.

Canceling the Combining Task

If you wish to cancel the task before it completes, either click the [Cancel] button on the Progress window or press the Esc key.

Tip	To abort the calibration before it is finished, click the [Cancel] button on the progress window or press the Esc key. Mira will prompt you for confirmation to quit. If you confirm, the task will terminate immediately.

If the This window option is selected for the List results in option, Mira logs processing messages in the Results box at the bottom of the dialog. Messages appear after the processing finishes. The Results field has a right-click menu as shown below. Using this menu you can save messages to a text file and copy from the box to the Windows clipboard or a Mira Text Editor. Only selected (highlighted) text is copied. Commands for editing and copying the text are available in a pop-up menu opened by right-clicking inside the results box. The menu is shown below. You can also elect to save the messages to a Text Editor which offers similar functionality as well as printing capability.

To prevent accidental deletion of calibration messages, you cannot clear text simply by highlighting and deleting the text using the mouse. To clear messages, you must use the Clear command in the pop-up menu.

Combining Strategy

Canceling the Combining Task

Related Topics