Changes between Version 8 and Version 9 of IPP_Progress_Report_20111205

Timestamp:

Dec 13, 2011, 4:31:50 PM (15 years ago)

Author:

eugene

Comment:

--

IPP_Progress_Report_20111205

@@ -5 +5 @@
 
 === Eugene Magnier ===
+
+ * fixed the OFF_CHIP bug introduced recently (flag was raised for all detections due to a mismatch of images)
+ * psphotStack was failing to measure the photometry for the matched positions.  This was due to the models not being generated for the matched sources, but it also led me to an issue with the matching process : the match radius was too small, so many faint objects were not correctly matched.  Some objects in the wings of bright stars were also likely to be mis-matched (or result in matches that probably should not be generated). I addressed this by bumping up the match radius somewhat.
+ * Extensive communications with Doug trying to understand the faint end non-linearity in his analysis of the MD photometry.  He has updated his model to include a constant flux offset for all objects in a given exposure (if, eg, the sky were off, or something equivalent).  This offset scales with FWHM^2^ as one would expect if the sky were off.  The odd thing is that the offset is such that all fields and all filters have nearly the same offset in DN per pixel.  In other words, if this is an error in the sky subtraction (over-subtracting the sky), the error that is made is always the same amount, regardless of the sky flux and the crowding.  This seems surprising.  I ran a set of tests with modifications to the sky analysis (using the algorithm which is more robust, but possibly more sensitive to crowding) to see if this affects the results.  
 
 === Serge Chastel ===