[alma-config] Guess it...

[Stephane Guilloteau]

To Bryan's point
    1) given a fixed physical size limit, what flavor of array would you design then?


    That is indeed the right question, beyond any doubt

    2)  now, if you can come up with a ring/donut which has nearly as good an imaging
capability as the more condensed spiral, and that has twice the resolution,
which would you choose?


    My reply to that is that having "as good imaging capability" and "twice the resolution"
 is a conflicting request. To get resolution, you have to sacrifice something (brightness
 sensitivity, sidelobes, deconvolution stability, ...). The best of both worlds does not exist,
 so that we have to define an acceptable compromise.
 
 That's our job. Moreover, we don't have yet the definition of "good imaging quality" (as
 pointed out by Eric Keto, current estimates of image quality may depend on the imaging tool)

To Min's argument

 1)  I had somehow in mind that nobody ever disputed that even the 3 km "configuration" had
to be a ring-like or similar thing. 

2) Concerning brightness, the compact array only gives you optimal brightness at the largest
angular scales. Our problem is mostly multiscale (see below)

3)  The resolution is not an absolute number because distance convert it to different angular
scales... So we have to figure out if among the limited range of resolutions we can afford
given the site, there is any PHYSICAL value which makes a step in our astronomical knowledge.  This can occur for various reasons (e.g. the distance to the nearest star,
nearest star formation region, nearest galaxy, etc...)   Once we get such a number, 
we could try to optimize imaging quality for this number (sensitivity + deconvolution error
amplification)

            Stephane


    
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