[daip] uvsub

[Eric Greisen]

robert becker writes:
 > hi, i am doing wide field A confg mapping. i use Imagr with tiling
 > and see a very bright source way off axis. When I tile the mao I get
 > one position for the source, when I don't tile I get a different position
 > (no surprise). which position is the right one to use in UVSUb if I want
 > to subtract the source from the uvdata, ie, does uvsub do it right or not?
 > 

If you feed the multi-facet model (either all facets or the one 3-D
facet with the external source) you should get the same subtraction as
done in IMAGR in the first place.  So use the position from the facet.
 A large-field no-facet will have a radial position error.

Eric Greisen