Mask pixels inside or outside a specified circle in a two-dimensional NDF


This routine assigns a specified value (which may be bad) to either the outside or inside of a specified circle within a specified component of a given two-dimensional NDF .


outset in out centre diam


The co-ordinates of the centre of the circle. The position must be given in the current co-ordinate Frame  of the NDF (supplying a colon ":" will display details of the current co-ordinate Frame). The position should be supplied as a list of formatted axis values separated by spaces or commas. See also Parameter USEAXIS. The current co-ordinate Frame  can be changed using task WCSFRAME.
The NDF array component to be masked. It may be "Data", or "Variance", or "Error" (where "Error" is equivalent to "Variance"). ["Data"]
The constant numerical value to assign to the masked pixels, or the string "bad". ["bad"]
The diameter of the circle. If the current co-ordinate Frame of the NDF is a SKY Frame (e.g. RA and DEC), then the value should be supplied as an increment of celestial latitude (e.g. DEC). Thus, "10.2" means 10.2 arcseconds, "30:0" would mean 30 arcminutes, and "1:0:0" would mean 1 degree. If the current co-ordinate Frame is not a SKY Frame, then the diameter should be specified as an increment along Axis 1 of the current co-ordinate Frame. Thus, if the current Frame is PIXEL, the value should be given simply as a number of pixels.
IN = NDF (Read)
The name of the source NDF.
If a TRUE value is supplied, the constant value is assigned to the inside of the circle. Otherwise, it is assigned to the outside. [FALSE]
OUT = NDF (Write)
The name of the masked NDF.
Title for the output NDF structure. A null value (!) propagates the title from the input NDF to the output NDF. [!]
USEAXIS is only accessed if the current co-ordinate Frame of the NDF has more than two axes. A group of strings should be supplied designating the axes that are to be used when specifying the circle via Parameters CENTRE and DIAM. Each axis can be specified using one of the following options.
  • Its integer index within the current Frame of the input NDF (in the range 1 to the number of axes in the current Frame).

  • Its Symbol  string such as "RA" or "VRAD".

  • A generic option where "SPEC" requests the spectral axis, "TIME" selects the time axis, "SKYLON" and "SKYLAT" picks the sky longitude and latitude axes respectively. Only those axis domains present are available as options.

A list of acceptable values is displayed if an illegal value is supplied. If a null (!) value is supplied, the axes with the same indices as the two used pixel axes within the NDF are used. [!]


outset neb1 nebm "13.5,201.3" 20 const=0
This copies NDF neb1 to nebm, setting pixels to zero in the DATA array if they fall outside the specified circle. Assuming the current co-ordinate Frame of neb1 is PIXEL, the circle is centred at pixel co-ordinates (13.5, 201.3) and has a diameter of 20 pixels.
outset neb1 nebm "15:23:43.2 -22:23:34.2" "10:0" inside comp=var
This copies NDF neb1 to nebm, setting pixels bad in the variance array if they fall inside the specified circle. Assuming the current co-ordinate Frame of neb1 is a SKY Frame describing RA and DEC, the aperture is centred at RA 15:23:43.2 and DEC -22:23:34.2, and has a diameter of 10 arcminutes.

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