[daip] tvdist

[R. Craig Walker]

TVDIST looks like it would be useful to me (I had not seen it before), but
I have a bit of a problem.  When I run it, I can get two identical
positions despite moving the cursor (maybe not clicking on the second), or
I can get different positions with the shifts reporting something
reasonable (although the sign convention is a bit interesting) but the
separation and PA being zero, or I can get what look to be complete
results.  It may be sensitive to which button are pushed, or the magnitude
of the separation, or something else - I haven't found the pattern yet.

Here is a case with ok shifts but not ok distance and PA.

>tvdist
AIPS 1: 'MOVE CURSOR TO END POINT, HIT ANY BUTTON'
AIPS 1: Got(1)  user= 500  disk= 6  type= MA   BW090N3C274.CMEAN.1
AIPS 1: IMXY : position TV cursor, then push button A, B, C, or D
AIPS 1: IMXY:    54.00   54.00
AIPS 1: 'MOVE CURSOR TO START POINT, HIT ANY BUTTON'
AIPS 1: Got(1)  user= 500  disk= 6  type= MA   BW090N3C274.CMEAN.1
AIPS 1: IMXY : position TV cursor, then push button A, B, C, or D
AIPS 1: IMXY:    86.00   73.00
AIPS 1: The distance between RA 12 30 49.42330208 , DEC 12 23 28.0444949
AIPS 1:                  and RA 12 30 49.42337852 , DEC 12 23 28.0438299
         is
AIPS 1:      0.00000 arc seconds at position angle   0.00 degrees
AIPS 1: Shift =  0.0011200 -0.0006650 arc seconds


The first click was about on the core position.  To try to see which
of the above positions that is, I looked at the image header:
AIPS 1: Observed RA   12 30 49.423    DEC  12 23 28.04
That's not too useful with 0.000035" pixels.

Cheers,

Craig

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    R. Craig Walker            Array Operations Center
    cwalker at nrao.edu           National Radio Astronomy Observatory
    Phone  575 835 7247        P. O. Box O
    Fax    575 835 7027        Socorro NM 87801   USA
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