- Form: AUTOCEN buf [N=n] [SIZE=n] [STEP=n] [C=(r,c)]
[PLOT]
AUTOCEN attempts to find the center of an extended and possibly amorphous
object by use of reflected autocorrelation. It is designed for objects
like globular clusters. For smooth objects, the AXES command is better. The
routine works by calculating a set of correlation amplitudes about an
estimated image center. Amplitudes are measured on an N X N grid with
sampling taken at STEP spacing in pixels. At each sample point the mean is
calculated in a SIZE X SIZE pixel cell, and is subtracted in calculations
of the autocorrelation amplitude, which is calculated by the product of the
cell with its image reflected about its center. The default values for N,
SIZE, and STEP are 7, 75, and 4. The final center is calculated by fitting
a paraboloid to the grid of amplitudes. The results are saved in the VISTA
variables AXR and AXC, and in the AXES common block. If the PLOT keyword
is specified, a cross is marked at the determined center on the TV image.
See Also: AXES