[daip] about TVLABEL

[Eric Greisen]

Kazuya Hachisuka writes:

 >  >imh

 > AIPS 1: RA---SIN   256    05 32 47.321     128.00      -0.000200    0.00
 > AIPS 1: DEC--SIN   256   -05 24 16.630     129.00       0.000200    0.00

 > AIPS 1: Phase shifted in X      4.672  in Y      7.170


You appear to have done an enormous shift (measured in pixels).  I
wonder if the integration time in the correlator will have smeared you
data badly for such a large shift.  At least yoou appear to have set
DO3DI to true in IMAGR.  In a "3D" shift, the tangent point of the
data is shifted, not just the center of the image.  Therefore the
reference pixel (defined to be at the tangent point) is at the new
coordinate, in the center of your new image.  When you TVLOD the whole
image, LTYPE=4 and LTYPE=5 will produce the same results when the
reference pixel is at the center of the image (as it is in your
image).

If you were to TVLOD with TBLC = 128, TTRC=256 (not usually a sensible
operation on a small image) and then do TVLABEL with LTYPE 4 and LTYPE
5 you would see the difference in the 2 labeling types.

Eric Greisen