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Basic Information on demos
Task: demos
Purpose: Inverse mosaicing operation
Categories: map manipulation
DEMOS (de-mosaic) is a MIRIAD task which takes a model of the sky
(which is primary beam corrected), and then multiplies by a primary
beam response function at a number of different pointing
centers. It produces a different output for each pointing center.
Thus this task performs the inverse of mosaicing. The input pointing
centers and the primary beam size are indirectly specified by
a visibility dataset.
Because the output of DEMOS have primary beams applied, they can
be used for comparison with visibility data and uncorrected images. In
particular SELFCAL cannot handle a model which is primary beam
corrected, though it can handle a visibility data file containing
multiple pointings. Thus you could use DEMOS to break the model into
several models which are not primary beam corrected.
Key: map
This is the name of image, that is to be de-mosaiced. No default.
The input is primary beam corrected image, single dish image, or
one that is partially primary beam corrected (e.g. the output
of MOSMEM).
Key: vis
This is one or more input visibility datasets. The pointing centres
and primary beams corresponding to the selected visibilities are used
in the de-mosaicing process.
Key: select
Normal uv selection. See help on select. Generally you will select
only those pointings of interest.
Key: out
This gives a template name for the output images. The actual output
image names are formed by appending a number corresponding to each
pointing center to this output name. For example, if out=cygnus,
then the output images will be called cygnus1, cygnus2, etc.
Key: imsize
This gives two values, being the output image size, in x and y.
If no value is given, then the outputs will be one primary beam
width in size. If one value is given, then this is used for both
x and y. Each output size might be smaller than this, to prevent
each output from extending beyond the edges of the input image.
Key: options
Extra processing options. There is currently only one option.
detaper This indicates that the input image is not fully
primary beam corrected. Such images are formed by
LINMOS with options=taper or by MOSMEM.