[daip] UVCON

[Leonia Kogan]

Hi Andy,

First of all I want to answer your concern about primary beam correction 
at UVCON.

You are right UVCON doe  not carry out the primary beam correction if 
the model is given as SMODEL
On the other hand there is no sence at all at the primary beam 
correction simulation if  the model is the point (SMODEL(4)=0), and not 
so much even if SMODEL(4)=1 (gaussian)
Taking into account that implementation of primary beam correction at 
the case of SMODEL is rather complicate
I arrive to the decision to add only the warning if the user put input 
parameters to get primarry beam correction
with SMODEL.

By the way I found that UVCON does not carry out the primary beam 
correction when the model is given as a set of the clean component but 
the clean components are not point. Again I add the worning instead of 
very serious change of UVCON to serve such an exotic case..

Thank you for pointing out to the UVCON problem!

Now about your last e-mail:

Andy Biggs wrote:

> Hi Leonia. Sorry to bother you again, but I have some more questions 
> about UVCON. I'm trying to simulate some observations at L-band and 
> want to get the noise characteristics right. The IN2FILE allows me to 
> input a file containing Tsys as a function of elevation and I've got 
> those from a graph in the Observational Status Summary. But I'm 
> confused about the efficiency - is this a function of elevation? My 
> feeling is that it should be about 0.55 at all elevations, but the 
> example files in the UVCON help have it varying with elevation.

You are wrong. Generally speaking efficiency of antennas depends on 
elevation because of the dependence of
dish deformation and other reason. VLA antennas for exemple designed to 
have maximum efficiency at elevation 45 degrees.

>
> Also, I've been DBCONing separate UVCON files together and mapping 
> them in IMAGR. Surprisingly, the noise doesn't seem to decrease as 
> sqrt(t).

I do not know the answer. If you really want to investigate the problem 
you'd leave aside DBCON
and play with different TIMERANG at IMAGR. But you have to remember that 
changing  timerang you change
UV coverage and rms of  a complex image can depend on the UV coverage 
and not only of time.

Cheers  Leonia

>
> Cheers,
>
> Andy