Name
       strehl - Strehl ratio computation

Synopsis
       strehl [options] <cubes...>

Description
       strehl  computes the Strehl ratio for every plane in every
       cube given on command line. See ALGORITHM to know  how  it
       is  computed.   strehl needs to know some parameters about
       the mirror and  observation  wavelength  to  generate  the
       ideal  PSF.  Defaults  for  these parameters are taken for
       Adonis, use the options  to  feed  other  values.   strehl
       accepts jokers on command line :
       > strehl *.fits

       ATTENTION!  The input image must be square (same size in x
       and y), and this size shall be a power of 2! This to allow
       a correct PSF generation.

Algorithm
       For each image in each cube (candidate image), the follow-
       ing algorithm is applied:

       1. Generate a PSF for a given telescope configuration  and
       observation wavelength.

       2. Normalize the PSF and candidate image to unity flux.

       3. Do Strehl = MAX(candidate) / MAX(PSF)
       Where MAX is the maximum pixel in the image.

       Attention:  the theoretical PSF is generated only once per
       call! When giving several cubes on command-line, it is  up
       to  the  user  to check that the same parameters are valid
       for all files (check the wavelength).

Options
       -g     An ideal PSF is generated for Strehl ratio computa-
              tion.   Using   this  option,  a  FITS  file  named
              `strehl1.fits' is generated in the  current  direc-
              tory, containing the generated ideal PSF (of Strehl
              ratio equal to 1). Use it to cross-check  that  the
              generated PSF fits your computation.

       -p PrimaryDiameter
              Primary  mirror  diameter  in  meters.  Defaults to
              3.47. This value is actually 3.60 meters, corrected
              to take into account the central obscuration ratio.

       -d SecondaryDiameter
              Secondary mirror diameter in  meters.  Defaults  to
              1.66. This value is actually 1.57 meters, corrected
              to take into account the central obscuration ratio.

       -l `lambda0 dlambda'
              Do  not  forget the simple quotes around the 2 val-
              ues. First  value  is  the  central  wavelength  of
              observation. Second value is the filter width. Val-
              ues are given in microns (1e-6 m).
              Defaults to 2.2 and 0.3.

       -s pixelscale
              Pixel Scale in arc seconds. Defaults to 0.05.

Example
       To compute the strehl ratio over 10 cubes named  S001.fits
       to  S010.fits,  on  an  8 meter telescope with a 1.5 meter
       secondary mirror, a central wavelength of 5.0 um and  fil-
       ter width of 0.1 um, a pixel scale of 0.05, use:

       strehl -p 8 -d 1.5 -l `5 0.1' -s 0.05 S*.fits

Files
       Files shall all comply with FITS format

See Also
       stcube