Changes between Version 24 and Version 25 of stacking_coverage.20130307

Timestamp:

Apr 24, 2013, 2:42:47 PM (13 years ago)

Author:

watersc1

Comment:

--

stacking_coverage.20130307

@@ -1 +1 @@
 == 2013-04-24 ==
 
+The following images review the statistics for the SAS g.00000 data in four processings:
+
+ * SAS_v8.  This is the current public release version of SAS, and was generated on 2012-07-19 22:32:40 with software_ver 34160.
+ * SAS123.ipp. This is a reprocessing of SAS using the current IPP tag (2013-04-19 23:59:00 with software_ver 35266).  This is taken as the default against which the others are measured.
+ * standard.  This is the initial proposed set of stacking changes, including SAFE=F, circularization fix, and bimodal input rejection. (2013-04-24 03:41:11/35307M)
+ * unrestricted. This is identical to the standard reduction above, but sets the minimum input threshold to 10.0pxl (only inputs above that are rejected with the bimodal code).  (2013-04-24 03:41:11/35307M)
+
+First, fraction of input images accepted into the stack (positive good).  The SAS_v8 reduction had no input clipping, and so all excluded inputs are rejected at the PSF matching phase.  The proposed standard reduction is somewhat more aggressive than the current tag, likely as a result of the "year 3" data having slightly different seeing than the "year 1+2" data.  This induces a bimodality that the rejection code picks up on.  The unrestricted reduction is more inclusive of things with slightly larger sizes, and due to the fixes in the chi!^2 matching, excludes fewer images than the SAS_v8.
+
 [[Image(acceptance.png,600px)]]
+
+Fill factor (positive good) is not very surprising.  Turning safety off results in much better fill factors compared with the previous reductions.
+
 [[Image(fill_factor.png,600px)]]
+
+The .num files (positive good) contain the number of input images that contributed to a given pixel.  This is largely a reflection of the acceptance plot above, showing that as we exclude more input images, the average contributions to a given pixel drops.  The unrestricted reduction offers a median improvement of about 0.4 inputs/pixel, with the other reductions having little change.  
+
 [[Image(pixel_num.png,600px)]]
+
+The above data suggests that switching to the unrestricted option (which will only clip the worst outliers) is probably a good idea.  The concern for this is that we will increase the size of the target PSF.  Correcting the circularization bug seems to help constrain the targets reasonably well.  The SAS_v8 reduction did not have this correction, and did not restrict any inputs, and has the largest PSF size.  The standard reduction clips strongly to keep the target PSF size down, and as such, does not increase it relative to the current tag.  The unrestricted PSFs are larger than the current tag, but looking at the histogram of FWHM values, it does not seem to push to extreme values, with nearly all targets smaller than 8pxl.
 
 [[Image(fwhm.png,600px)]]
 [[Image(fwhm_hist.png,600px)]]
-
 
 == 2013-04-23 ==