[daip] Re: problem in IMAGR

[Eric Greisen]

Craig Warner writes:
 > Hi.  I'm running IMAGR on line data and it keeps giving me the following
 > error messages:
 > 
 > charon> IMAGR1: **** WARNING data discarded outside usable part of UV
 > plane ****
 > charon> IMAGR1: **** Actual Umax 5.3586E+03 exceeds limit 3.5814E+03
 > ****
 > charon> IMAGR1: **** Use cellsize <  13.36714 not  20.00000 to get all
 > data ****
 > charon> IMAGR1: **** using a U guard band of  0.300 of a radius
 > ****
 > charon> IMAGR1: **** WARNING data included out of inner portion of UV
 > plane ****
 > charon> IMAGR1: **** Watch for high-frequency & other poor cleaning
 > effects ****
 > 
 > I have the UV Range set at 0-40,000 so I don't know what the 3581 Umax
 > limit it complains about it.  I have a cellsize of 20, and the beam is 60,
 > so I don't know why it says use cellsize <13.36.  Can you figure out
 > what's going wrong?  Thanks.

      The size of the UV plane grid is determined by the IMSIZE and
CELLSIZE (loosly = IMSIZE/CELLSIZE).  This message states that you
have visibility data out to 5359 wavelengths, but the largest spacing
that will fit on the grid is 3581.  It has thrown away all your
longest spacings since they do not fit - this will change the shape of
your beam and make it fatter than it would be if you used correct
imaging parameters.  Try decreasing the cells size (I recommend 10)
and doubling IMSIZE and examine the beam pattern that comes out.  You
will see significant differences between the 2.

Eric Greisen