Changes between Version 10 and Version 11 of QUB_MDS_diff_analysis_20091221

Timestamp:

Dec 21, 2009, 6:37:28 AM (17 years ago)

Author:

kpat.uk

Comment:

--

QUB_MDS_diff_analysis_20091221

@@ +1 @@
+
+
+'''Summary of outcomes from QUB tests and Paul's UK Visit'''
+
+ISIS and ppsub appear to give similar results (with Paul's new version of
+ppsub with the major normalisation bug vix)
+
+- if we choose the correct order of the convolution then ppsub gives reasonably
+good subtractions, and dual convolution is not required. We saw good
+subtractions even with different psfs of FWHM~6 and 9 in the reference and input images
+(4 gaussian with the same order (2) as in the default parameters of
+ppSub. This gives 24 elements in the matrix and 71 degrees of freedom) 
+
+- if we do not use the convolved stack as the reference, we get results that we
+are much more comfortable with, and can do our own photometry on the difference
+images much more confidently. We take Paul's point about the advantages of convolution
+but we see more reliable analysis, from standard photometry measurements with the unconvolved stacks.
+
+- Our tests show there would be a huge gain (in quality and masking) if we implement the following strategy :
+  create a High-Quality reference image per MDS per filter (good seeing, around 0.9")
+  
+this HQ-reference need only be one night of stable seeing, dithers combined without magic
+
+  always convolve HQ-reference to the new epoch (assume we will not get <0.9" often)
+
+  always sigma-clip and combine the 8-dithers at any epoch (*without* MAGIC) and give us the stack, we don't need the dithers
+
+  we will volunteer to pick the HQ-reference for each field and filter
+
+  for the HQ-reference, ideally on a good night we could aim for ~16 dithers to make sure we get full coverage of the edges
+
+
 '''REMOVAL OF SPURIOUS SOURCES FROM DIFFERENCED CMF FILES'''