Changes between Version 112 and Version 113 of MD_WSdiffim_photcheck_test20121004

Timestamp:

Feb 27, 2013, 11:18:11 AM (13 years ago)

Author:

Mark Huber

Comment:

--

MD_WSdiffim_photcheck_test20121004

@@ -16 +16 @@
 The MD10 sequential exposure pair, asteroid (12891) example was used to trace through the code to identify problems. The camera SMF exposure photometry was taken as the "true" target photometry to achieve from the diffim photometry. Offset of exposure photometry to some predicted/expected magnitude is a different problem altogether. 
 
-Key problem -- coordinate list for determining PSF was a matched+merged list of both the input and reference image rather than just a matched list (poor PSF resulting in 0.3+ irregular mag). When the list is sorted by inst_flux and the top hardcoded 500 sources are used, ones that are not in the input warp from masking etc reduce the available "good" sources. Normally that is only a small fraction, but when a deeper refstack is used the missing sources have a much higher inst_flux and begin to dominate the set for determining the PSF making for a poor solution. Newer MD refstacks have been much deeper, some fields before (typically y-band) had only order 10-20 inputs, and now have 60-100.
-
-Various other minor issues identified:
+Key problem -- coordinate list for determining PSF was a matched+merged list of both the input and reference image rather than just a matched list (poor PSF resulting in 0.3+ irregular mag). When the list is sorted by inst_flux and the top hardcoded 500 sources are used, ones that are not in the input warp from masking etc reduce the available "good" sources. Normally that is only a small fraction, but when a deeper refstack is used the missing sources have a much higher inst_flux and begin to dominate the set for determining the PSF making for a poor solution. Newer MD refstacks have been much deeper, some fields before (and typically in y-band) had only order 10-20 inputs, and now have 60-100.
+
+Various other minor(?) issues identified:
  * background binning for photometry on diffims has not been the same as other photometry (~0.1-0.2 offset mag) -- using 128 for now, may need additional/proper tuning
- * psphot trace level >5 modifies the photometry output -- still to be fixed
+ * psphot trace level >5 modifies the photometry output -- not operation still to be fixed
  * refConv outputs aren't needed since magic not used -- turning off in gpc1/psphot.config
-  * This output highlighted another possible problem in the COMP_WT output where the range is insufficient and cores of moderately bright sources are clipped to NAN -- unknown extent and how to fix
+  * This output highlighted another possible problem in the COMP_WT output where the range is insufficient and cores of moderately bright sources are clipped to NAN -- unknown extent or if critial and how to fix
  * ppSub missing -threads option in help -- to be fixed
  * sometimes a check is made for a single input list of sources (input or ref) and allowed with the one provided being the master source list, other places if either doesn't exist then ppSub exits so that sources for both must be provided -- unclear if one source list is acceptable for all parts, still to be addressed
  * REVERSE is wanted as a command line argument and not defined for choosing if the input or the reference is used to determine the PSF for photometry on the diffim -- ever necessary?
  * is convolved refstack really necessary here or would the unconvolved stack be better (basically the refstack is just sky for moving objects but for other transient science may want unconvolved) as the unconvolved stack is typically of better FWHM and requires less deconvolution to the warp seeing -- needs to be investigated further
- * psphot run on diffim compared to ppSub photometry does not necessarily agree -- 
+ * psphot run on diffim compared to ppSub photometry does not necessarily agree -- unclear still if config/setup or actual problem/bug
+
+
+== Issue of photometry offset ==
+
+Exposure (SMF) photometry versus diffim photometry: unless the target is contaminated with background (self or host), photometry at the exposure level will be the better choice for photometry. To test, a large sample will need to be run, like the MD09 event. 
+
+
+Predicted/expected photometry versus exposure photometry: beyond the scope of diffim photometry investigation.