[alma-config]My point of view

[Mark Holdaway]

> 
> So I want to make the two statements:
> 
> 1. If I optimise sidelobes inside the less circle (say one or less PB radius)
>    the side lobes could be better (I think twice or more). They would be less 
>    than 2-3%
> 
> 2. I do not belive that the PSF with a PB can be described as a multiplication 
>    of the original PSF by Primary beam or any other function.

I want to remind the group that David Woody and I both arrived at the same
answer from totally different paths (the sqrt(2) wider Gaussian is the
implementation of David's result, which I moderately disagree with, though
I see why it is there), David from measurement orthoganality, me from an
analysis of the imaging algorithms.  I also disagree with Bryan that this
is ad hoc, I think it is rigorous for mosaicing.

>   The following analysis excludes the mosaic because I am not familia with 
>   the detail of mosaic
> 
> Lets consider the sky with center at the PB center.
> Lets PSF maximum points to the direction determined by the vector de 
> and a sidelobe of the PSF is determined by the vector eshift.
> Then the position of the sidelobe relatively the position of the PSF's 
> maximum is 
> 
> e = eshift-de
> 
> The sky signal coming to the sidelobe will be attenuated by the PB 
> at PB(eshift) 
> 
> and the signal coming from the direction of the max PSF
> be attenuated by the PB at PB(de) 

But IS there any signal coming from that direction?

> So the modified PSF (PSFmod) when we clean the component from the direcrion de 
> can be described by the following equation:
> 
> PSFmod(e) = PSF(e) * PB(e+de) / PB(de)   (1)

I don't understand why you are dividing by the PB?
In the mosaic process, you never divide by the PB.

> So the function we have to use to multiply PSF is not the constant 
> function but depend on the position of the clean component relatively 
> PB center.
> 
> So if we want to compare configurations using the worst side lobe metric we 
> need to calculate (eq 1) the worst side lobe inside of the given circle 
> for pointing PSF at all components inside of this circle.
> 
> Leonia


	-M