[alma-config] Re: Near-in sidelobes

[Mark Holdaway]

> 
> Using a smaller Gaussian beam to get around the problem of weak 
> sources on the Gaussian wing of a brighter source is not a real
> answer -- we are all familiar with problems associated with
> super-resolution, and this ad hoc answer goes against what makes
> the Gaussian dirty beam attractive.  

Hey, if its two sources 0.5 beams apart, you move to the next
array configuration, which resolves the sources nicely.
What, you are already at the largest array configuration?
Hey, its a ring array anyway!

> The VLA example I mentioned 
> was just an illustration of the problem I was trying to describe.  
> As Leonia will discuss further in his own e-mail, the dirty beam
> from zoom spiral has a large wing around it, most of which also
> has to be negative (to have zero net power under the beam, the
> true dirty beam should have a negative DC offset).  I suspect the
> ring of near-in sidelobes in the donut arrays will ultimately
> limit its imaging capability at some point, but the Gaussian
> wing, which is negative, is also of some concern.

Rather than speculate theorize, lets go further and figure out what sorts
of imaging problems will be affected by the broad wing.  It seems
that imaging very large sources would be.  So lets find the cases
and figure out how big (or small) the effects are.

	-M