Changeset 41968 for branches/eam_branches/ipp-20211108/psphot/src/psphotSignificanceImage.c

Timestamp:

Dec 25, 2021, 2:22:11 PM (5 years ago)

Author:

eugene

Message:

allow option to use signal image on first pass for detections

File:

• branches/eam_branches/ipp-20211108/psphot/src/psphotSignificanceImage.c (modified) (2 diffs)

branches/eam_branches/ipp-20211108/psphot/src/psphotSignificanceImage.c

@@ -105 +105 @@
               //              float v2 = value + PS_SQR(value/100.0);
               // CZW 2013-06-20: I don't think this hack was helping.
+              // EAM 2021-12-21: see note below about divots in the significance image
               float v2 = value;
               smooth_wt->data.F32[j][i] = factor * PS_SQR(v2) / smooth_wt->data.F32[j][i];
@@ -122 +123 @@
     }
     psImageConvolveSetThreads(oldThreads);
+
+    // We now have the significance image and the signal image.  In some cases (e.g.,
+    // stacks), the variance on pixels in the cores of stars is elevated compared to pure
+    // poisson statistics.  In this case, especially at high signal levels, the ratio of
+    // signal / noise in the core of the star can be lower than the surrounding ring of
+    // pixels.  This results in a divot in the center of the star in the significance
+    // image.  the apparent peak of the significance is then not centered on the star and
+    // chaos ensues.  A possible fix is to use the signal image for signficance for
+    // the high S/N detection pass.
 
     pmReadout *significanceRO = pmReadoutAlloc(NULL);