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frame-to-frame shifts




  Okay, here's my contribution: I used the positions of stars
in a sub-cell (500x500) pixels near the center of the V-band
frames to determine the shifts relative to image hvra2157634.
Here's a table of the differences I found:

     1 lists hvra2157634 hvra2157611 dr =   3.36 dc = -77.13   175 of  218 
     2 lists hvra2157634 hvra2157613 dr =   2.82 dc = -71.10   184 of  222 
     3 lists hvra2157634 hvra2157615 dr =   2.35 dc = -65.27   191 of  227 
     4 lists hvra2157634 hvra2157616 dr =   1.88 dc = -59.31   185 of  214 
     5 lists hvra2157634 hvra2157618 dr =   1.39 dc = -53.33   195 of  225 
     6 lists hvra2157634 hvra2157620 dr =   0.97 dc = -47.38   192 of  217 
     7 lists hvra2157634 hvra2157622 dr =   0.84 dc = -41.43   194 of  220 
     8 lists hvra2157634 hvra2157623 dr =   0.63 dc = -35.38   195 of  214 
     9 lists hvra2157634 hvra2157625 dr =   0.45 dc = -29.36   206 of  228 
    10 lists hvra2157634 hvra2157627 dr =   0.33 dc = -23.47   221 of  239 
    11 lists hvra2157634 hvra2157629 dr =   0.20 dc = -17.53   217 of  232 
    12 lists hvra2157634 hvra2157630 dr =   0.19 dc = -11.66   233 of  253 
    13 lists hvra2157634 hvra2157632 dr =   0.06 dc =  -5.84   234 of  246 
    14 lists hvra2157634 hvra2157634 dr =   0.00 dc =   0.00   240 of  249 
    15 lists hvra2157634 hvra2157636 dr =  -0.07 dc =   5.81   240 of  249 
    16 lists hvra2157634 hvra2157638 dr =  -0.23 dc =  11.68   250 of  268 
    17 lists hvra2157634 hvra2157639 dr =  -0.23 dc =  17.43   236 of  258 
    18 lists hvra2157634 hvra2157641 dr =  -0.31 dc =  23.21   229 of  247 
    19 lists hvra2157634 hvra2157643 dr =  -0.40 dc =  28.98   235 of  261 
    20 lists hvra2157634 hvra2157645 dr =  -0.37 dc =  34.70   227 of  250 
    21 lists hvra2157634 hvra2157646 dr =  -0.42 dc =  40.42   216 of  243 
    22 lists hvra2157634 hvra2157648 dr =  -0.52 dc =  46.19   217 of  246 
    23 lists hvra2157634 hvra2157650 dr =  -0.43 dc =  51.90   225 of  257 
    24 lists hvra2157634 hvra2157652 dr =  -0.54 dc =  57.56   207 of  235 
    25 lists hvra2157634 hvra2157653 dr =  -0.71 dc =  63.29   217 of  251 
    26 lists hvra2157634 hvra2157655 dr =  -0.78 dc =  68.91   202 of  238 
    27 lists hvra2157634 hvra2157657 dr =  -0.83 dc =  74.40   216 of  260 
    28 lists hvra2157634 hvra2157659 dr =  -1.02 dc =  80.00   224 of  294 
    29 lists hvra2157634 hvra2157661 dr =  -1.02 dc =  85.62   186 of  227 
    30 lists hvra2157634 hvra2157662 dr =  -1.10 dc =  91.03   140 of  161 
    31 lists hvra2157634 hvra2157664 dr =  -1.13 dc =  96.64   194 of  239 
    32 lists hvra2157634 hvra2157666 dr =  -1.17 dc = 102.08   206 of  257 
    33 lists hvra2157634 hvra2157668 dr =  -1.21 dc = 107.50   195 of  248 
    34 lists hvra2157634 hvra2157669 dr =  -1.24 dc = 112.87   182 of  241 
    35 lists hvra2157634 hvra2157671 dr =  -1.46 dc = 118.22   175 of  232 
    36 lists hvra2157634 hvra2157673 dr =  -1.43 dc = 123.57   169 of  221 
    37 lists hvra2157634 hvra2157675 dr =  -1.42 dc = 128.81   161 of  218 
    38 lists hvra2157634 hvra2157677 dr =  -1.45 dc = 134.14   161 of  222 
    39 lists hvra2157634 hvra2157678 dr =  -1.47 dc = 139.42   175 of  247 
    40 lists hvra2157634 hvra2157680 dr =  -1.63 dc = 144.53   161 of  220 
    41 lists hvra2157634 hvra2157682 dr =  -1.64 dc = 149.77   164 of  231 
    42 lists hvra2157634 hvra2157684 dr =  -1.67 dc = 154.91   155 of  224 
    43 lists hvra2157634 hvra2157685 dr =  -1.59 dc = 160.04   157 of  226 
    44 lists hvra2157634 hvra2157687 dr =  -1.87 dc = 165.22   162 of  239 
    45 lists hvra2157634 hvra2157689 dr =  -1.93 dc = 170.40   150 of  229 
    46 lists hvra2157634 hvra2157691 dr =  -1.73 dc = 175.46   160 of  245 
    47 lists hvra2157634 hvra2157693 dr =  -1.81 dc = 180.50   150 of  237 
    48 lists hvra2157634 hvra2157694 dr =  -1.85 dc = 185.30   149 of  243 
    49 lists hvra2157634 hvra2157696 dr =  -1.65 dc = 190.27   149 of  239 

  When I plot the difference as a function of image number (the first column),
I see a linear trend in the column offsets (North-South), and a nearly
linear trend in column offsets (East-West); the only big difference from
linearity occurs in the column offsets for images 1-8.  In those
early images, the column offset is much _larger_ than its value
in later images.

  I haven't yet looked at the I-band data.  Sorry.

                                                     Michael