[daip] DBCON

[Eric Greisen]

achung at astro.umass.edu writes:
 > Hi,
 > 
 > I like to combine Cs and D array data but I'm having hard time
 > with DBCON. I calibrated two data set separately and I'm trying
 > to concatenate SPLIT data (single source), but DBCON says:
 > 
 >   casper> DBCON1: Task DBCON  (release of 31DEC07) begins
 >   casper> DBCON1: New reference day is 20050805
 >   casper> DBCON1: Scaling u,v,w of data set 2 by  9.9785775E-01
 >   casper> DBCON1: Scaling u,v,w of data set 1 by  9.9892870E-01
 >   casper> DBCON1: RA and DEC match to within 1 microarcsecond each
 >   casper> DBCON1: --I'm not going to shift positions
 >   casper> DBCON1: FREQUENCIES DIFFER BY TOO MUCH:  1.41141872D+09 
 > 1.41013327D+09
 >   casper> DBCON1: MULTI-FREQUENCY DATA BASES INCOMPATABLE
 >   casper> DBCON1: Purports to die of UNNATURAL causes
 > 
 > I also tried -1 for dopos(2,1) or specified FQTOL and they all
 > return the same error. Is there anything that I am missing here?
 > 

I am assuming that these are 2 data sets with multiple channels that
you intend to image in a single continuum data set.  The problem is
that aips has to correct the recorded u,v,w for each channel by 
(Delta nu) / nu0.  The Delta nu's are probably the same but the nu0 is
different by 1.3 Mhz or 1/1000 making the frequency correction be in
error by 1 cell for a 1K by 1K image.

Send me the 2 headers and let me think about it a bit to see if the
task is too fussy.

Eric Greisen