Level 2 Help for CLEAN

1. blurred image.
2. point spread function.

1. delta function image.
2. residual image (input after psf removals).
3. delta function image convolved with psf.

algorithm gain. Each time a point spread function is subtracted from the
image the amplitude of the psf is set to GAIN* the DN of the pixel.
Default is 0.2
Large point spread functions should have smaller gains.

Standard deviation of the noise.
Iterations will cease when the residual falls below NOISE.
Defaults to 2.0
This test usually stops the algorithm in the case MODE=POSITIVE.

Maximum permitted umber of iterations.
Defaults to 1,000,000

Iterations will cease when the percent reduction in the residual becomes 
less than CHANGE.
Defaults to 4.0
This test usually stops the algorithm in the case MODE=TOTAL

The maximum number of times a pixel can be modified. This keeps clean
from cycling between a small set of pixels comprising artifact
which cannot be subracted as point spread functions.
Defaults to 200

The mode of operation.
There are two modes:

TOTAL where the point spread function can be positive or negative.
This mode will match the input image very well but will create negative
intensities in the restored image.

POSITIVE where the point spread function can only be positive.
This mode will not match the input image very well but will create
positive intensities in the restored image.

Default is TOTAL.

Causes the input image to be convolved with the point spread function
before any other operations. The default is for the first input to be
convolved already.