Calibrating Images
Images often need to be calibrated to convert observed values to standard values that correctly represent measurements in the real world. Calibration may be done in two realms:
Luminance (or "intensity"). This calibration converts the pixel values to a proportional or exact representation of the true signal. The calibration may also be in terms of physical units.
Spatial Dimension. This calibration converts positions on the image from the native pixel coordinates of (column,row) to a world coordinate system, such as the celestial coordinate system of Right Ascension and Declination.
After calibration, image values and positional measurements may be made using the calibrated system. For example, after spatial calibration is performed, image positions, distances, and angles are measured and reported in the calibrated units. FITS format supports these types of calibration. Therefore, a calibration may be permanently saved to the image file if the image is saved in FITS format. Mira provides a number of tools to accomplish calibration:
You also may wish to create synthetic images with or without artificial stars to evaluate your calibration techniques and to explore the propagation of noise through your processing strategy.
Contents, Pixel Coordinate Definition, Subpixel Coordinate Definition, Tutorial: Introduction to Astrometric Calibration