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-seconds.

     -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  cen-
     tered  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