SEE_ALSO

## NAME

fradius -- Compute the radius of a PSF.

## USAGE

`fradius input output`

## DESCRIPTION

This task computes the radius of the point spread function (PSF)
as an indication
of how far each image is out of focus.
This task computes the radius directly,
while the `faradius` task computes the radius of the autocorrelation.
A line of output is written for each row of boxes
(read from the input file from the `fextract` task).
For each box along a row, the position of the PSF is determined by taking
the average of X and Y, weighted by pixel value.
The sums of values and values multiplied by distance from this position
are then accumulated, combining values for different boxes along the row.
The radius is the sum of values multiplied by
distance divided by the sum of values.

## PARAMETERS

- input = "" [string]
- Name of input image.
The output from the
`fextract`task provides the input to this routine.

- output = "" [string]
- Name of output text file which will contain two values per row: the refoc mirror position (read from the input header) and the characteristic radius.

## EXAMPLES

## BUGS

## REFERENCES

This task was written by Phil Hodge.