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