TOPPED-Remove all pixel values above a certain limit from
an NDF image file
Description:
Sets to bad, all the pixels with a count above the threshold
level. An option allows the close neighbours of the bright pixel
to be set to bad as well. Close neighbours are considered to be
those pixels within a user defined radius of the bright pixel.
A further option allows all bad pixels in the output image to be
assigned a random value. The values chosen are taken from a
Normal distribution defined by the user.
Usage:
TOPPED IN OUT WIDTH BACK SIGMA NSIGMA NOISE PSIZE
Parameters:
BACK = _REAL (Read)
The background count value. Units counts.
IN = _NDF (Read)
The name of the NDF that is to be examined.
NOISE = _LOGICAL (Read)
Defines whether or not bad pixels should eventually be
assigned a random value.
NSIGMA = _REAL (Read)
The number of standard deviations above sky at which the
cutoff occurs.
OUT = _NDF (Write)
The name of the output NDF that will be created.
PSIZE = _REAL (Read)
The size of each pixel in arc seconds. If the image contains
a SKY co-ordinate frame this value will be determined
automatically.
SIGMA = _REAL (Read)
The background pixel count standard deviation value. Units
counts.
WIDTH = _REAL (Read)
The width of the circle around a bright pixel within which
pixels will be set to bad. Units arc seconds.
Uses EGGS as the input image and finds all pixels within the
image that have a count greater than 1000.+8.x23. These are
all set to the bad value. In addition, all pixels within a
radius of 1.25 arc seconds are also set to bad.
Uses OBJECTS as the input image and finds all pixels within
the image that have a count value greater than 6200.+10.x390..
These are all set to random values, as are all the pixels
within a radius of 2. arc seconds. Pixel size in arc seconds
will be determined if possible from the WCS component of the
image.
Notes:
The distribution of pixel values used when NOISE=TRUE comes
from a Normal (Gaussian) distribution. In some circumstances,
particularly for low count values, this may not be appropriate.