[daip] Re: position question

[Eric Greisen]

Pat Palmer writes:
 > Eric,
 > 
 > I have been trying to get more accurate positions from SAD and haven't
 > figured out how to do it.
 > 
 > The info I have been able to get is:
 > ----------------
 > >From JMFIT
 > Model fit to NW3OH_65_R  .ICL001.   1
 > X-ref pix=1024.0  RA 02 27 03.7756660  
 > Y-ref pix=1025.0  DEC 61 52 24.447990
 > 
 > from IMHEAD
 > Filename=NW3OH_65_R  .ICL001.   1
 > RA---SIN  1024    02 27 03.776    1024.00      -0.002000
 > DEC--SIN  1024    61 52 24.448    1025.00       0.002000
 > Phase shifted in X      0.000  in Y     -0.325
 > 
 > from SAD
 > NW3OH_65_R  .ICL001.      1     Disk  3     Plane    1     User     347
 > Reference Center: 02 27 03.7762  61 52 24.453
 > 
 > ---------------
 > 
 > Because I need to be able to get positions from SAD to 0.1 mas, I need
 > one more significant figure than is given by the reference position.
 > The offsets from SAD have plenty of significant figures, but I can't
 > figure out how to get the SAD reference position to more accuracy
 > 
 > The IMHE shows that the image center is offset, the orignal center
 > seems to be output for JMFIT as this same center, but with more
 > significant figures.  But I can't get the reference center to the from
 > these numbers, presumably because of projections.
 > 
 > I tried MFPRT, but it does not output the reference center at all, only
 > the offsets.
 > 
 > I remember last week you suggested one more place to try, but I forgot what
 > it was.

The display of Reference Center in SAD had an error causing the values
to be 0.0005 sec of time and 0.005 sec of arc too large.  This same
error applied also to sexagesimal strings written out for non-VLB like
resolutions.

Corrected in tomorrow's MNJ.

Eric Greisen