Request to enable psphot to work for difference images

[Michael Wood-Vasey]

It is vital to both the MOPS and Transient Science Client (TSC) projects to be able to do a full end-to-end test on simulated data and data from other projects on difference image detection. A key to doing this is adding the ability to psphot to process difference images. I know this is already on the to-do list; this request is just to express the priority of importance from the TSC perspective. This is the very next most important thing to be added to the IPP for TSC to progress to truly being an integrated effort with IPP rather than just a collection of modules in search of data.

Thanks,
Michael

[Paul Price]

Some code is in-place, needs to be checked and tested.

[Paul Price]

Works. In the process, Gene discovered a bug in the way histograms were being implemented that was affecting our statistics, and I found that the variance maps from applying convolution kernels were not correct (can't just convolve by the square of the normal kernel, but also need to preserve the scaling). These issues have been fixed, and I have used psphot from within ppSub (and stand-alone) to do photometry on subtracted images.