[daip] Fwd: Re: Imagr

[Eric Greisen]

-------- Forwarded Message --------
Subject: Re: Imagr
Date: Tue, 20 Nov 2018 08:36:53 -0700
From: Eric Greisen <egreisen at nrao.edu>
Organization: National Radio Astronomy Observatory
To: DINIL BOSE <dinilbose at gmail.com>

On 11/19/2018 07:29 PM, DINIL BOSE wrote:
> Dear Professor,
> 
> Thank you for your great software AIPS.
> I am using AIPS for more than a year for analysing GMRT data. Its wonderful.
> 
> Lately, I am wondering about the Imagr  task. How the algorithm of the 
> task works?. If I set a uvrange what is really happening?. I couldn't 
> find a document for my questions.
> 
> Do you have a document which is specifically about the algorithm of 
> Imagr task?.
> 
> Thank you for your time
> Dinil Bose

Thank you.

The explain file for IMAGR does give a lot of information.  UVRANGE is 
simply a limit on the sqrt(u*u+v*v) values of the data included in the 
image.  In other words, it inserts a sharp edge in the UV distribution 
by excluding samples outside the specified annulus.  Such sharp edges 
are actually not very desirable so things like taper and the weighting 
options probably are better.  UVRANGE is applied on a per spectral 
window basis so spectral channels just outside UVRANGE will get included.

The IMAGR multi-scale methods are described in the appendix of
    Greisen, E. W., Spekkens, K., & van Moorsel, G. A. 2009, "Aperture
       Synthesis Observations of the Nearby Spiral NGC 6503: Modeling
       the Thin and Thick Disks", AJ, 137, 4718-4733


I hope this helps.  Let me know if you have other questions.

Eric Greisen