Changes between Initial Version and Version 1 of psphot_detection_comparison

Timestamp:

Mar 8, 2011, 2:44:44 PM (15 years ago)

Author:

watersc1

Comment:

--

psphot_detection_comparison

@@ +1 @@
+I tested the object detection efficiency of psphot by running psphot
+on a number of images supplied by Jim:
+
+1) ps1_i_sub.fits/ps1_i_sub_mask.fits/ps1_i_sub_wts.fits
+
+   This image was a composite mosaic Jim put together from four MD04
+   reference stack frames.  This composite mosaic does not include the
+   covariance information from the original stacks, which clearly impacts
+   the object detection.  The CMF from this run has 7884 PSF objects
+   (5658 with non NULL PSF_INST_MAG), and 1354 xsrc objects.  The image
+   with non-NULL mag PSF objects overplotted shows a number of missed
+   objects along with faint objects and objects that do not appear real.
+
+[[Image(image1.png)]]
+
+2) i_sdss_sub.fits/i_sdss_sub.mask.fits/i_sdss_sub.var.fits
+
+   This is another composite mosaic of SDSS images.  The original images
+   had no covariance information, so it is not lost during this
+   processing.  The CMF from this run has 712 PSF objects, all of which
+   have non-NULL PSF_INST_MAG, and 169 xsrc objects.  All objects
+   detected in this image appear to be real, and there are only a few
+   cases where a real-looking object is not detected.
+
+[[Image(image2.png)]]
+
+
+3) subaru_ip_064_sci_20.fits/subaru_ip_064_sci_20.mk.fits/subaru_ip_064_sci_20.wt.fits
+
+   This is a deep Subaru image with mask and variance created by setting
+   the mask to all zero (accept all pixels) and the variance image equal
+   to VAR = SCI + 21.19**2, where 21.19 is a quick estimate of the image
+   noise.  The CMF contains 2015 PSF objects (1989 with not-NULL
+   PSF_INST_MAG) and 25 xsrc objects.  The low number is almost certainly
+   due to the poor variance image model, which excludes the majority of
+   the faintest objects.
+
+[[Image(image3.png)]]
+
+
+4) MD04.V2.skycell.078.stk.179047.unconv.fits/MD04.V2.skycell.078.stk.179047.unconv.mask.fits/MD04.V2.skycell.078.stk.179047.unconv.wt.fits
+
+   This is one of the raw MD04 reference stack frames used in the mosaic
+   above.  This retains the covariance information, and the associated
+   CMF file shows a much better correspondance between image and detected
+   objects.  The CMF has 16417 PSF objects (16212 with non-NULL
+   PSF_INST_MAG) and 1276 xsrc objects.  Although there are a large
+   number of detections, the majority appear to associate with very faint
+   objects.
+
+[[Image(image4.png)]]
+
+5) subaru/MD04 unconv comparison
+
+   To check how many of the objects detected in the MD04 reference stack
+   correspond to real faint objects, the detection list from #4 was
+   overlaid on the image from #3.  Although there are some detections
+   that do not associate with real objects on this deeper image, it does
+   appear that the majority of the faint detections from #4 are real.
+
+[[Image(image5.png)]]