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One of the main difficulty of the short-spacing problematic is the need of
observations from a single-dish telescope different from the
interferometer. In this respect, the IRAM-30m and PdBI are very
complementary. Nevertheless, when observing with the single-dish telescope,
a few precautions are needed to avoid contaminating the interferometric
data with possible artifacts of single-dish data.
- The field-of-view of the single-dish map must be twice the
field-of-view covered by the mosaic. The only exception to this rule
happens when the source intensity decreases to zero in a smaller
field-of-view. Indeed, there is no point in observing an empty sky.
- The observing strategy must enforce Nyquist sampling (or better) of
the source at the resolution of the single-dish telescope.
- A particular care should be taken of the pointing, tracking and
amplitude calibration and baseline removal as those are critical issues
in obtaining a high quality single-dish map to produce short-spacing
information. For instance, data with too large tracking errors should be
discarded.
- We advise to make many On-The-Fly coverages of the observed
field-of-view to get homogeneous observing conditions. Scanning in
perpendicular directions is needed to decrease stripping.
Sometimes, single-dish telescope time is scarce and some of the above
criteria can not be fulfilled. In those cases, you can still try to use
your single-dish observations and our algorithm will try to make its best
to get a sensible result. However, any artifact in the combination may
directly come from wrong single-dish observations. In other words, do
not blame the software unless you are sure of the quality of the
quality of your single-dish (and interferometric) observations...
Next: How to use your
Up: Practical considerations
Previous: When are short-spacing information
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Gildas manager
2014-07-01