• The southern declination boundary at +12 degrees is evident.
• Isolated northern tiles between +12 degrees and +48 degrees stand out. Does this have to do with hardware period?
• A very dark patch (circled) shows a block of data that is most significantly out of line with the rest (a blink of the ccd/cmd for this block against neighboring regions below shows the photometric offset). The block is at (decl between 18. and 24. and ra between 228.2 and 230.2). Comparison was made with the same dec range but ra between 224. and 226. The shift is probably in the J-band alone give the right/left shift in the CMD and the diagonal shift in the CCD. The sources in this region come from 1997-06-14 and 1997-06-15. Further examination (the last plot below) shows that the shift is restricted the to the block of data taken in the first block of the night on 1997-06-15. The magnitude of the miscalibration is 0.12 mag based on the average J-band magnitude for sources brighter than K_s=13.0 on June 14 vs. June 15. The aperture and PSF photometry produce identical results suggesting that calibration, rather than a bad PSF issue, is to blame.

Followup:

Reference to the "sit" files for v2 and v3 reveals a problem.

Below are the records for June 15 in v2 and v3.

The problem scans (139-152) all have their J-band zero
point identically set to "0".  

In v2 the value for these scans was closer to -0.03.  
In v3 the adjacent scans have a value closer to -0.06. 
This offset (0.06 mag relative to the subsequent scans in v3) 
would go a long way toward correcting the problem seen in v3 data.

V3:

 scan    jzp       hzp        kzp       date

  139 |       0 | -0.0536 | -0.0153 | 1997-06-15
  140 |       0 | -0.0531 | -0.0148 | 1997-06-15
  141 |       0 | -0.0526 | -0.0144 | 1997-06-15
  142 |       0 | -0.0521 | -0.0139 | 1997-06-15
  143 |       0 | -0.0516 | -0.0134 | 1997-06-15
  144 |       0 | -0.0511 | -0.0129 | 1997-06-15
  145 |       0 | -0.0507 | -0.0124 | 1997-06-15
  146 |       0 | -0.0502 | -0.0119 | 1997-06-15
  147 |       0 | -0.0497 | -0.0114 | 1997-06-15
  148 |       0 | -0.0492 | -0.0109 | 1997-06-15
  149 |       0 | -0.0487 | -0.0104 | 1997-06-15
  150 |       0 | -0.0482 | -0.0099 | 1997-06-15
  151 |       0 | -0.0477 | -0.0094 | 1997-06-15
  152 |       0 | -0.0472 | -0.0089 | 1997-06-15
  166 | -0.0586 | -0.0434 |  -0.005 | 1997-06-15
  167 | -0.0581 | -0.0429 | -0.0045 | 1997-06-15
  168 | -0.0575 | -0.0424 |  -0.004 | 1997-06-15
  169 | -0.0569 |  -0.042 | -0.0035 | 1997-06-15


v2:

  139 | -0.0325 | -0.0407 |  -0.007 | 1997-06-15
  140 | -0.0325 | -0.0407 |  -0.007 | 1997-06-15
  141 | -0.0325 | -0.0407 |  -0.007 | 1997-06-15
  142 | -0.0325 | -0.0407 |  -0.007 | 1997-06-15
  143 | -0.0325 | -0.0407 |  -0.007 | 1997-06-15
  144 | -0.0325 | -0.0407 |  -0.007 | 1997-06-15
  145 | -0.0325 | -0.0407 |  -0.007 | 1997-06-15
  146 | -0.0325 | -0.0407 |  -0.007 | 1997-06-15
  147 | -0.0325 | -0.0407 |  -0.007 | 1997-06-15
  148 | -0.0325 | -0.0407 |  -0.007 | 1997-06-15
  149 | -0.0325 | -0.0407 |  -0.007 | 1997-06-15
  150 | -0.0325 | -0.0407 |  -0.007 | 1997-06-15
  151 | -0.0325 | -0.0407 |  -0.007 | 1997-06-15
  152 | -0.0325 | -0.0407 |  -0.007 | 1997-06-15
  165 | -0.0325 | -0.0407 |  -0.007 | 1997-06-15
  166 | -0.0325 | -0.0407 |  -0.007 | 1997-06-15
  167 | -0.0325 | -0.0407 |  -0.007 | 1997-06-15
  168 | -0.0325 | -0.0407 |  -0.007 | 1997-06-15
  169 | -0.0325 | -0.0407 |  -0.007 | 1997-06-15
  170 | -0.0325 | -0.0407 |  -0.007 | 1997-06-15
  171 | -0.0325 | -0.0407 |  -0.007 | 1997-06-15

The whirlgif below compares "good" calibration from jun14 to the original "bad" calibration from jun15 and to the corrected jun15 calibration.