[Almasci] Re: [mmaimcal]Re: Comment in ALMA memo 489

[Mark Holdaway]

> 
> mark,
> 
> do you mean that the CLEAN components are weighted by the mask value,
> or that it it treated in the way that stephane noted would be good - i.e.,
> that the "mask" is used to determine the probability of finding a
> CC at a particular location?

It is more like the mask in AIPS++ determines the probability
of finding a CC at that location.  Non-binary masks are possible,
though we don't have much experience with them.  If as mask is
0.5, then a component needs to be twice as bright to be cleaned
as a component of the same brightness where the mask is 1.0.

  -M

> 
> i guess i'm confused about just how a mask works in practice when
> its values are not 1 or 0...
> 
> 	-bryan
> 
> 
> On 2004.04.07 10:03, Mark Holdaway wrote:
> > 
> > Perhaps this helps:  in AIPS++, the mask need not be [0|1], but can be
> > anywhere in between -- so the edge of the PB Mask can be dithered, or, 
> > whatever it is called when you make the jagged edge of a diagonal line 
> > look smooth by giving the pixels on the edge some appropriate value
> > between 0 and 1.  Then again, perhaps I am misunderstanding you
> > entirely?
> > 
> >    -M
> > 
>