[alma-config] Re: CONFI

[John Conway]

Hi Leonia,

  Let me know how I get the updated CONFI code, I'd like
to try it.

Whateveer the array 'style', rings, spirals,  whatever
ultimately it might be interesting to optimise with both 
beam metrics and uv metrics (a la Fomalont) or a mixture. 
These metrics should also probably also force some degree 
of natural uv taper and forcing of short  baselines, since from  
imaging simulations these both seem to be  desirable  
properties, 

I guess  one way of  looking at minismising far sidelobes 
in CONFI is that it is  producing uv coverages  which don't have 
periodicities  (such periodicites are obvioulsy bad 
because these then allow into the final image  false unseen 
distributions which  correspond to compact structure). As you alluded 
to in  the telecon if one uses some over simple  uv metric like 
fraction of uv cells sampled then you could imagine 
getting uv  coverages with the same score in the uv metric but 
one of the two having much higher dirty beam sidelobes. Making the 
uv metric more complex can obviously mitigate this problem 
but it seems natural that if  one  is trying to reduce periodicties 
in the uv  coverage  then looking at the Fourier transform of this 
uv coverage (i.e dirty beam) would be  a natural thing to do(!). 
The other practical advantage of the sidelobe minimisation is 
that you have  devised an efficent optimisation algorithm.
Whether a dirty beam minimisation is the only/best  thing one should 
aim for is a different question. I'm sure we will talk a lot about
metrics again in Tuscon, my position is pragmatic, we can write down 
half a dozen properties of the uv coverage/beam that are 
desirable, some of them hard to have simultaneously, deciding the 
balance between these different properties needs some imaging 
simulations as a 'reality check'. 

As far as running the new CONFI here we don't have a midnight job or
anything like that here (and I understand there will be no more
offcial classic AIPS releases), could you put the .FOR 
code on an anoymous site somewhere? In short whats the
best way to get it?

 Cheers
  John.

P.S Where can I get the ASCII version of the masks?
I had a quick look at Bryans web page but I didn't see
it there yet.

 

On Fri, 3 Mar 2000, [Leonia Kogan] wrote:

> John,
> 
> As you know CONFI (AIPS task) can read the topography information as 
> an input file written in ASCII.
> The original file prepared by Bryan was in fits format.
> Recentely he created the files in ASCII format also.
> 
> These files are much bigger than the Holdaway's file I have used early.
> So I modifyed CONFI to read the Bryan's ASCII files.
> 
> I have changed some defaults of CONFI in accordance of last development 
> of ALMA.
> 
> I added the new parameters BLC, TRC to allow using a portion of the mask 
> for smaller configuration.
> 
> The new version of CONFI is in the AIPS system now.
> 
> Be ready to see that CONFI works rather slow with the huge file.
> 
> Leonia
>