Syntax
Document.AlignImages ( Mode, Bicubic[, Images] )
Parameters
AlignType Mode - specifies method used to align images
mxAutocorrelation (0) : autocorrelation
mxAutoStarMatch (1) : automatic matching of star brightnesses and separations
mxAstrometric (3) : WCS information in the FITS header
mxPlanetary (4) : aligns centroids of the principal disk found in each image
mxAutoOneStar (5) : aligns centroids of the brightest star found in each image
Boolean Bicubic - specifies whether bicubic interpolation will be performed
Collection Images- [optional] a Collection or Dictionary object whose members are the images to be aligned
Returns
Nothing
Remarks
Adjusts all documents in the collection Images so that the their image stars coincide with those in this document. The optimal positional adjustments required for each image are automatically determined using the algorithm specified by Mode. Autocorrelation is a mathematical procedure which determines the image shift for each image to minimize the deviation from the reference. Star matching searches for similar triangles formed by the twenty brightest stars in each image; it can translate, rotate, and scale images into best alignment. Astrometric alignment requires that each image (including the reference) have been solved, usually by PinPoint; using the plate solution, it determines how much to translate, rotate and scale the images into correspondence. Planetary alignment works only on images containing a large, bright, round object such as the disk of a planet, and shifts the images so that the centroids of these disks are aligned. Auto one-star alignment is intended for use on small subframes or cropped images containing a single dominant star; the images are shifted such that the centroids of this star are aligned.
Note that Mode cannot be set to the mxNoAlignment alignment technique used with CombineImages and CombineFiles.
The required translation is almost never an integral number of pixels, and therefore it is necessary to interpolate into the source image to estimate what the pixel values are at fractional coordinates. If Bicubic is False, the interpolation is performed on a small tilted plane bounded by the four surrounding pixels. If Bicubic is True, a cubic interpolation surface is used instead; this can give smoother results.
The set of images to be aligned is specified by the Images parameter, a Collection object to which has previously been added all the Documents which are to be aligned. Alternatively this parameter can be omitted, in which case all open images are aligned.
If any image cannot be aligned using the specified technique, AlignImages fails.
This method is equivalent to the Align Images command.