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What aperture should I use for large mosaics?

Optimum Aperture for Mosaicing:
What aperture should I use for large mosaics?
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A new ACS aperture, WFCENTER, has recently been defined. Its main feature
is that it encompasses the full Wide Field Camera field of view, and has
its reference point at the center of the field of view. This aperture is
designed for observations which are expected to be repeated with
relative rotations of 90 or 180 degrees on the same field. Since the
reference point lies very close to the inter-chip gap, WFCENTER is *not*
the preferred aperture when the need is simply to center a target in the
full field of view of the Wide Field Camera. For this, use aperture WFC.
The aperture WFCENTER may be used in configuration ACS/WFC in ACCUM mode
in the same manner as WFC with no special restrictions.
WFCENTER will not yet work properly if you include it in your RPS2 file
because software changes need to be made.  If you feel that WFCENTER is
needed for your science program, please consult your Program Coordinator.