Changes between Version 4 and Version 5 of Durham_MDS_Testing4

Timestamp:

Nov 23, 2009, 1:49:34 AM (17 years ago)

Author:

shaun.cole@…

Comment:

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Durham_MDS_Testing4

@@ -10 +10 @@
 
 Shown is the SDSS comparison for PSF mags on the ps1-md MD08 skycell 041 i-band stack 30204 (left) and Heather's previous stack (29871) on the same cell. Blue points are SDSS classified stars. Both have nominally the same exposure time (equivalent to 41 240sec exposures) and we assume come from the same set of exposures. However, the seeing is 2.0" on 30204 but only 1.4" on 29871, and the zero points differ by about 0.4 mags (note: the zero point for 29871 has the expected value).  Clearly there are problems with the stellar photometry being non-linear.
+
+[[Image(30204-v-29871-ap.jpg,600px)]]
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+However - above we show a direct IPP aperture magnitude (AP_MAG) comparison between 30204 and 29871. This is gratifyingly linear, from which we deduce there must be some problem in fitting the PSFs.