VISTA re-acquisition test

 The following data frames were used to test re-acquisition on 20090531 and 20090603. In the CASU naming convention the files used were:
v20090531_00218.fit, v20090531_00219.fit, v20090531_00220.fit, v20090531_00221.fit, v20090531_00222.fit  and
v20090603_00198.fit, v20090603_00199.fit, v20090603_00200.fit, v20090603_00201.fit, v20090603_00202.fit

These are two 5 point dithers of the same region. They were observed at roughly the same airmass (hour angles were 4 and 13 minutes west) so refraction problems are going to be minimal.

 After the usual 2d processing and catalog generation for each image, the positions of the objects were matched for a given observation and a given detector for 20090531 and 20090603 (there were roughly 9-10K objects that matched per detector). The median differences in x,y coordinates between the two observations can then be worked out. The diagrams interspersed with this text represent  each observation pair and show a vector diagram of the positional residuals as a function of position on the focal plane. (The rough pixel positions of the centre of each detector is the origin of each arrow). The arrows are magnified by a factor of 2000 so that they are visible. All five of the plots look very similar which is encouraging.  There does however seem to be some residual rotation between the two sets of observations. The largest residuals are approximately 0.5 pixel. This falls well within the target of 1 pixel specified.

The tables used in the plots are included below with columns: detector#, xpos, ypos, dx, dy.

v20090531_00218.fit vs v20090603_00198.fit

1    1024.00       1024.00      0.200       -0.361
2     3942.40       1024.00      0.201      -0.319
3     6860.80      1024.00      0.334      - 0.246
4     9779.20      1024.00      0.430       -0.188
5     1024.00       4915.20      0.127      -0.302
6     3942.40       4915.20      0.143      -0.244
7     6860.80       4915.20      0.215     - 0.179
8     9779.20       4915.20      0.355      -0.117
9     1024.00       8806.40      0.058      -0.275
10    3942.40      8806.40      0.054      -0.209
11    6860.80      8806.40      0.106      -0.161
12    9779.20      8806.40      0.303       -0.070
13    1024.00     12697.60     -0.071      -0.225
14    3942.40     12697.60     -0.014      -0.143
15    6860.80     12697.60      0.050     -0.075
16    9779.20     12697.60      0.228       0.013

v20090531_00219.fit vs v20090603_00199.fit

1 1024.00 1024.00  0.035 -0.535
2 3942.40 1024.00  0.158 -0.459
3 6860.80 1024.00  0.220 -0.376
4 9779.20 1024.00  0.312 -0.300
5 1024.00 4915.20 -0.004 -0.479
6 3942.40 4915.20  0.104 -0.394
7 6860.80 4915.20  0.153 -0.297
8 9779.20 4915.20  0.255 -0.188
9 1024.00 8806.40 -0.089 -0.354
10 3942.40 8806.40  0.061 -0.260
11 6860.80 8806.40  0.113 -0.168
12 9779.20 8806.40  0.170 -0.090
13 1024.00 12697.60 -0.149 -0.207
14 3942.40 12697.60 -0.000 -0.107
15 6860.80 12697.60  0.045 -0.061
16 9779.20 12697.60  0.119  0.021
 

v20090531_00220.fit vs v20090603_00200.fit

1 1024.00 1024.00  0.094 -0.473
2 3942.40 1024.00  0.283 -0.397
3 6860.80 1024.00  0.356 -0.332
4 9779.20 1024.00  0.374 -0.251
5 1024.00 4915.20  0.053 -0.415
6 3942.40 4915.20  0.184 -0.345
7 6860.80 4915.20  0.264 -0.270
8 9779.20 4915.20  0.313 -0.180
9 1024.00 8806.40 -0.021 -0.286
10 3942.40 8806.40  0.074 -0.218
11 6860.80 8806.40  0.155 -0.155
12 9779.20 8806.40  0.175 -0.121
13 1024.00 12697.60 -0.169 -0.184
14 3942.40 12697.60  0.003 -0.126
15 6860.80 12697.60  0.033 -0.097
16 9779.20 12697.60  0.052 -0.018

v20090531_00221.fit vs v20090603_00201.fit

1 1024.00 1024.00  0.006 -0.443
2 3942.40 1024.00  0.141 -0.388
3 6860.80 1024.00  0.191 -0.308
4 9779.20 1024.00  0.318 -0.261
5 1024.00 4915.20 -0.081 -0.397
6 3942.40 4915.20  0.072 -0.332
7 6860.80 4915.20  0.111 -0.270
8 9779.20 4915.20  0.274 -0.163
9 1024.00 8806.40 -0.157 -0.285
10 3942.40 8806.40 -0.040 -0.228
11 6860.80 8806.40  0.035 -0.139
12 9779.20 8806.40  0.176 -0.066
13 1024.00 12697.60 -0.281 -0.216
14 3942.40 12697.60 -0.112 -0.138
15 6860.80 12697.60 -0.073 -0.079
16 9779.20 12697.60  0.072 -0.024
 

v20090531_00222.fit vs v20090603_00202.fit

1 1024.00 1024.00 -0.117 -0.435
2 3942.40 1024.00 -0.026 -0.403
3 6860.80 1024.00  0.121 -0.345
4 9779.20 1024.00  0.265 -0.251
5 1024.00 4915.20 -0.182 -0.372
6 3942.40 4915.20 -0.070 -0.312
7 6860.80 4915.20  0.084 -0.247
8 9779.20 4915.20  0.206 -0.155
9 1024.00 8806.40 -0.263 -0.280
10 3942.40 8806.40 -0.150 -0.209
11 6860.80 8806.40  0.014 -0.135
12 9779.20 8806.40  0.111 -0.057
13 1024.00 12697.60 -0.327 -0.188
14 3942.40 12697.60 -0.234 -0.090
15 6860.80 12697.60 -0.081 -0.025
16 9779.20 12697.60  0.036  0.038