[daip] ACFIT

[Jim Ulvestad]

Hi Colleen,

Sorry for the delay, had to do other things first.  I'm still not
sure I actually understand what you're trying to do, probably
because I've never done this myself.  (My apologies, but AIPS
is very short-handed at the moment, and we don't have the full
range of experience we'd like to have.)

When you make an SN table, the SN table refers to a specific IF
or set of IFs.  So you can't directly make an spectral template
and SN table from IF 2 and apply it to both IFs.

What I believe you would have to do is to make two data sets
using SPLIT or UVCOP, with a single IF in each. You could then 
run ACFIT on each data set, both times using the spectral template 
from IF 2.  This would give you an SN table and (after CLCAL)
a CL table for each IF.  Alternatively, I suppose you could do
the same thing by running ACFIT for only one data set, and then
copying the SN table over to the other one and running CLCAL there.

If you do this, then it looks to us as though it's at least 
possible to put the two data sets back together using UVGLU
(although we're not entirely sure why it's necessary to do this).

Anyway, try out this process and UVGLU, and let us know if
it works.

jim


Colleen Schwartz wrote:
> 
> Hi Jim,
> 
> Maybe that's where I'm going wrong - the signal is almost completely
> restricted to IF 2, but I want to figure out the gains for the entire data
> set, i.e. both IFs, since there are some weaker maser features in IF 1.
> But you can't run ACFIT on both IFs at once it seems.  So I was assuming
> that you can't just get the gains from IF 2 and apply that SN table to IF
> 1 too - or can you?
> 
> >From the cookbook, the best scheme I can come up with is to SPLIT up
> the IFs and then run ACFIT and KRING on both of them separately, but then
> I don't know how I could combine them again.
> 
> I've attached a spectrum, this is the template I wanted to use, it's the
> LA self-spectrum - perhaps it will help.
> 
> Thanks,
> Colleen
> 
> On Thu, 7 Sep 2000, Jim Ulvestad wrote:
> 
> > Hi Colleen,
> >
> > >From your first message, I expected that you only wanted to use one
> > IF to determine the gains.  But now this one looks like you want to
> > determine each IF separately.  So that confuses me a bit.  Do you
> > have the AIPS Cookbook?  If not, take a look at it on the web.
> > Pages 9-33 and 9-34 seem to describe the procedure, though not
> > quite perfectly.  It looks like you use SPLIT to copy off a
> > file with the self-spectra.  If you want to use only one IF as
> > an input, you need to set BIF and EIF in SPLIT to get the one
> > you want.  Then you run ACFIT, with the multi-source data file
> > as inname, and the single-source data file as in2name.  Here, you
> > have to pick which reference antenna you want to use for the
> > template, and which channels to fit.  This will make an SN table
> > attached to the original multi-source data set, which you must
> > then apply using CLCAL (perhaps after running SNSMO first).
> >
> > Again, let me know if this note plus the Cookbook is enough to
> > get you there.
> >
> > jim
> 
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