Name
       encircl - Encircled Energy Computation

Synopsis
       encircl [options] <cubes> <parameters>

Description
       encircl  computes  the encircled energy for every plane in a cube given
       on command line. See ALGORITHM to know how  it  is  computed.   encircl
       needs  to  be  given some parameters in order to work. These parameters
       are the approximate position of the peak on which  the  user  wants  to
       find  encircled  energy  radius, as well as the percentage of the total
       energy for which the radius is wanted.

Algorithm
       For each image in each cube (candidate image), the following  algorithm
       is applied:

       1. Check the validity of the window.

       2.  Find  the  position of the pixel of maximum intensity and re-center
       the window on that pixel.

       3. Calculate the energy encircled in the 100 % radius and  multiply  it
       by the percentage of the total energy for which the radius is wanted.

       4.  Calculate the encircled energy for every radius from 1 pixel to the
       100 % radius and store the results in an array.

       5. Look up the array to find the two entries whose values  are  nearest
       to  that  corresponding  to  the  percentage  of interrest of the total
       energy.

       6. Use a linear interpolation to find more precisely  what  the  radius
       is.

Options
       -p Plate Scale
              Plate  scale in arc-seconds per pixel, for an output in arc-sec-
              onds.

       -r Radius
              To override the hard coded size  of  the  100  %  energy  radius
              (1.4").

       -h half-size
              To override the default 20 pix value of the window half size.

Example
       To  determine  the radius for which the encircled energy is 50 % of the
       total encircled energy for an star whose energy we know to  be  located
       in  a  window  of 42x42 pixels roughly centered on pixel 60,60 of image
       star.fits with a plate scale of 0.1" we want to set the  100  %  energy
       radius to 1.1" use:

       encircl -h 21 -p 0.1 -r 1.1 star.fits 60 60 50

Files
       Files shall all comply with FITS format

See Also
       stcube, strehl