I am still beavering away at the PSF fit/Ensemble photometry stuff.
I'm glad it's called a "Status Report" and not a "Progress Report" as most of the progress has been, at best, lateral.
The PSF fit program reached its "final" form and the code got posted on my web site. This presumption was duly punished: when I reran Data Set 20 yet one more time, the same code came up, for some images, with completely different fits starting from different initial guesses. This is a known problem in this sort of optimisation but this is the first time I have seen it in this investigation. The problem, I think, is that I am now using the sum of 3 elliptical components in the PSF: this gives fit residuals as low as 5% which is a significant improvement over 1 or 2 (see various posts in the archives.) The three components ara allowed to change in size, shape and relative position across the image and the two different "optimum" solutions differ wildly in the relative motion ascribed to the components. In other words, the program is labelling components differently across the image in the different cases and having started off with an incorrect labelling is unable to correct this as the iteration "converges." Back to the drawing board.
The reason for rerunning Dat Set 20 was to accommodate "a few minor changes" in the ensemble photometry. What was supposed to be an entirely trivial change was to carry the Tycho2 designation of identified sources right through the process in a human-readable form: the previous version boiled the ID down to a single integer which was unique for that processing run but an absolute pain to turn back into the full Tycho2 identifier. While putting in this simple change, it looked as though I could easily stick in a unique identifier for the sources added during the processing. Things escalated from there ... it's nearly working but along the way I found some new bugs both in the PSF fitting code and in the Ensemble Photometry.
As I said: progress was mostly lateral.