Changes between Version 35 and Version 36 of staticsky.20120706_excess_detections

Timestamp:

Mar 28, 2013, 5:39:04 PM (13 years ago)

Author:

watersc1

Comment:

--

staticsky.20120706_excess_detections

@@ -18 +18 @@
 || 2296.5 || 2509.5 || -10.5183 || -10.4174 || -10.5561 || -10.5551 || -10.5770 || 2 ||
 
+This offset (~4 mag) is similar to the magCorr values listed below.  This prompted a scan of the code which led to the following conclusion:  We apply a magnitude correction to the sources used to construct the fake images.  However, we then compare those fake images to the convolved images that have not had a zpt/airmass/transparancy correction at all.  Therefore, when magCorr is large, it seems like we introduce an arbitrary offset.  I do not fully understand why input 4 shows this full effect, whereas input 2 has only a marginal shift.  Regardless of this uncertainty, I ran the test stack through processing with the magCorr correction disabled.  As shown in the counterpart to the image from 2013-03-27, the fake now closely matches the input convolved image.  The following table also shows that im2/im1 ~ 1.0 for all stamps in this region.
+
 [[Image(normalization2.jpg,800px)]]
 
@@ -32 +34 @@
 || 2144.500000 || 2449.500000 || 44486.904098 || 39580.071845 || 1.12397 ||
 || 2296.500000 || 2509.500000 || 16195.190695 || 14869.404454 || 1.08916 ||
+
+
+Continuing through to the output stack, the heavy mottling from before is gone, with an expected smooth noise pattern with slight bumps where the number of input frames is smaller.  Plotting up the image and variance profiles again for this new stack (scaled by a factor of 10 to not mask out the profiles from the old stack) shows that the image and variance frame now resemble each other, so the excess detections previously found on this stack should not be an issue.
 
 [[Image(stacks_noMagCorr.jpg,800px)]]