Changes between Version 6 and Version 7 of Stack_Sky_Levels

Timestamp:

Sep 4, 2013, 5:36:28 PM (13 years ago)

Author:

watersc1

Comment:

--

Stack_Sky_Levels

@@ +1 @@
+== 2013-09-03  ==
+
+=== Repeated background subtraction ===
+
+For a set of 465 i-filter warp images, I ran psphot to obtain a background level estimate.  This was done in three passes, to provide the standard background level (what we normally use), a second pass (showing the residual background remaining), and a third pass (checking that the residual had been removed).  The following table shows some statistics for these runs:
+
+|| Pass || Average background || Average background_sigma || Median background || Median background_sigma ||
+|| 1    || 2.14126 || 30.48071 || 1.931080 ||  28.195907 ||
+|| 2    || -0.0381096 || 30.51861 || -0.030491 || 28.232888 ||
+|| 3    || 0.00361354 || 30.52406 || 0.003190 || 28.226071 ||
+
+This suggests that we are leaving a residual background on the images, and only after three iterations is this background effectively fully removed.  
+
 == 2013-08-28 ==
 
@@ -44 +57 @@
 [[Image(psphot_bscale_check.png,400px)]]
 [[Image(psphot_offset_sigma.png,400px)]]
-