[daip] Smoothing option in IMAGR

[Kazi Rygl]

Dear Eric Greisen,

On Fri, 7 May 2010, Eric Greisen wrote:

> Kazi Rygl wrote:
> > Dear Sir/Madam,
> > 
> > I want to report a problem concerning the SMOOTH option in IMAGR for AIPS
> > versions DEC09 and DEC10. When imaging a spectral line data with the option
> > SMOOTH 1 0 (Hanning smoothing) and inspecting the image cube with ISPEC, I
> > noticed that the smoothing was not correctly applied: the spectral shape
> > remains as if unsmoothed.
> > I tried the same operation in the DEC08 version, where the spectral shape
> > was indeed altered by the smoothing.
> > 
> > Could you help me to overcome this problem?
> 
> SMOOTH is a basic parameter of the UV data reading and has not deliberately
> changed in many years.  It should be no different in recent versions than
> 31DEC08.  Look at the history file of the output image and see if SMOOTH
> appears there and what its values are.

In the history files of the images made with DEC10 and DEC08 I find the 
same line:
  1266  IMAGR SMOOTH(  1) = 1.00000E+00
 
> Try POSSM with SMOOTH in the various versions to see if SMOOTH fails there.

In POSSM (DEC10) SMOOTH works fine. 

> Try running SPLIT or SPLAT with SMOOTH and feeding the result into IMAGR with
> no SMOOTH.  IMAGR does so much to the data after the data are read that it is
> sometimes hard to see what is going on but without more to go on I cannot see
> how it could be failing.  I suppose I could try it again.

I did, as you suggested, a SPLIT with SMOOTH 1 0 and afterwards imaged 
the data using IMAGR with SMOOTH 0. In SPLIT SMOOTH worked properly!
I don't know why the SMOOTH option in IMAGR it did not work for me.
>From now on I will SPLIT the data before imaging them, and then my 
problem is solved.

Thank you very much for your fast reply & help!!

Kazi
> 
> Note I used SMOOTH=1,0 for a 24000 channel cube last December and it worked as
> intended (we had ringing in the spectra due to channels that were too wide).
> 
> Eric Greisen
>