NAME

noisepar -- Edit the noise model parameter set.

USAGE

noisepar

DESCRIPTION

The `noisepar' parameters specify the coefficients of the noise model used to estimate the `sigma', or statisical uncertainty, of the input image pixels that are averaged using various `wfpc' tasks. The total sigma is the square-root of the quadratic sum of the DN value (scaled by the detector `gain'), the CCD readout noise, and a term that scales as a percentage of DN.

Note that this is a parameter set (pset), not an executable task; it defines a set of parameters used by other tasks. Invoking the pset by name runs `eparam' on the parameter set, allowing the user to modify the parameters. Alternatively, the parameters may be modified on the command line by specifying the pset name and parameter name. For example, the user can type "noisepar.readnoise=2.0" to set the estimate of the readout noise to 2.0 DNs. Parameters can also be edited by using `eparam' on the calling task (e.g., by typing "eparam combine"), in which case, `noisepar' will appear as one of the task parameters; the `noisepar' parameters may then be edited by positioning the cursor on the line containing the pset name and typing ":e". After editing the pset parameters, type <Cntrl>-Z to return to the main task parameter menu.

PARAMETERS

(readnoise = 1.73) [real, min=0.]

Estimated readout noise (in DNs) of the input images. Note that the default value of 1.73 corresponds to 13 electrons if the inverse gain is 7.5 e-/DN.

(gain = 7.5) [real, min=1.e-6]

Detector gain in electrons/DN.

(scalenoise = 0.0) [real]

Multiplicative term in noise model, expressed as a percentage of a DN. That is, a value of 1.0 means a scalenoise of 1 percent.

SEE ALSO

combine, noisemodel