[daip] SAD reference center output question

[Eric Greisen]

Adam Ginsburg writes:
 > Dear Designated AIP,
 > When I run SAD on DBCON'd images vs. single-UV file images, it gives
 > different output.  The single-UV images give a reference center, e.g.
 > Reference Center: 11 20 15.0129  12 59 29.703
 > , and then list the RA and DEC relative to that center:
 >     #      Peak    Dpeak     Flux    Dflux    RA---SIN   DEC--SIN   Dx
 >      Dy       Maj     Min      PA    Dmaj    Dmin    Dpa
 >     1    352.572(112.386)  868.146(372.532)  -61.32310  -23.02841(
 > 0.16782 0.13419) 1.42381 0.70172  55.6( 0.45386 0.22368 16.8)
 > 
 > whereas the DBCON'd image gives output like:
 > #      Peak    Dpeak     Flux    Dflux       RA---SIN      DEC--SIN
 > Dx      Dy        Maj     Min     PA    Dmaj   Dmin  Dpa
 >     1    449.147(117.388)  616.219(252.486) 11 20 11.1336  12 58
 > 45.838(   0.116   0.318)    2.866   1.035   2.6(  0.749  0.270   9)
 > 
 > Is it possible to force them do display in the same manner?  I didn't
 > see any option in the SAD inputs, so perhaps the choice of relative
 > vs. absolute coordinates depends on something in the header?

The choice of display format depends on the axis increments in the
image.  If both are less than 0.1 arcsec then the "VLBI" format is
used.  That format has more digits in the coordinates and cares less
about absolute positions - both of which are realistic reflections of
what is meaningful in that sort of data.  The real estate in the print
display is in high demand and it is simply not possible to meet all of
the desirable forms at once.

Eric Greisen