-- AaronAndrews - 24 Nov 2016

Simulation: ( Simulation_test10.py.txt)

  • Made example star field with no background - used M103 data, 108 stars total. ( M103_Simtest_noBG.txt)
  • Modified simulation to generate position-varying background. Mean and standard deviation can be changed independantly.
  • For testing, generated means and standard deviations using following functions ('inclined planes'): ( M103_BG_1.txt)
    • Mean = 900 + (0.5)x + (0.005)y
    • S.D. = 5 + (0.01)x + (0.01)y
    • x,y = pixel positions
  • Could also generate with more complicated functions - e.g. taylor expansion.
  • Used mean and S.D. per pixel to generate random gaussian distributed value for background, added to example star field.
  • Size of the median filter box as a function of the fitted mean:
  • Used mean and S.D. per pixel to generate random gaussian distributed value for background, added to example star field:
  • M103_BGmean_1.png M103_BGsd_1.pngM103_BGfinal_1.png M103_starsBG_1_GS.png
Analysis
  • Ran a median filter (i.e. finding median of a box, size n, centered on each pixel) for different box sizes, on the simulated background+stars.
  • Subtracted the median image from original, to remove background. Then created histograms of resulting pixel values.
  • Histograms assumed to be gaussian - found sigma and mean for each.
  • Plotted sigmas and means in relation to box size.

  • Median, sigma and mean plots on simulated M103 with background, 65 width box:
    StatsPlotsM103SBG.png

  • Median, sigma and mean plots on simulated background, 65 width box:
    StatsPlotsSimulatedBG.png
  • Histograms showing the simulated background minus the median filter of the background for box sizes 201 and 11
  • For the 201 box size the fitted mean pixel value is 0.56057, the standard deviation is 15.992
  • For the 11 box size the fitted mean pixel value is 0.40479, the standard deviation is 15.634
M103_BackgroundOnly_Hist.png

  • Histograms showing the simulated background with stars minus the median filtered version for box sizes 301 and 15
  • For the 201 box size the fitted mean pixel value is 0.15810, the standard deviation is 16.386
  • For the 11 box size the fitted mean pixel value is 0.38595, the standard deviation is 15.972
M103_BackgroundStars_Hist.png

  • Size of the median filter box as a function of the fitted mean and the fitted standard deviation:
    compare.png

  • Images showing the simulated background minus the median filter of the background for box sizes 201 and 11:
M103_Background-Median_im.png

  • Images showing the simulated background with stars minus the median filter of the background for box sizes 201 and 11: M103_BackgroundStars-Median_im.png
Topic attachments
I Attachment History Action Size Date Who Comment
Texttxt BackgroundCode.txt r1 manage 5.5 K 25 Nov 2016 - 13:50 AnishaVadher  
Texttxt Background_Analysis.txt r1 manage 2.3 K 25 Nov 2016 - 13:07 LauraBevilacqua Background analysis code including median filter and histogram making
PNGpng BoxVsMean.png r1 manage 23.5 K 25 Nov 2016 - 11:14 AnishaVadher Size of the median filter box as a function of the fitted mean
PNGpng BoxVsSigma.png r1 manage 26.1 K 25 Nov 2016 - 11:16 AnishaVadher Size of the median filter box as a function of the fitted standard deviation
Unknown file formatfits M103_BG_1.fits r1 manage 12195.0 K 25 Nov 2016 - 11:05 AaronAndrews M103 sim. - BG only
PNGpng M103_BG_1.png r2 r1 manage 421.7 K 25 Nov 2016 - 13:26 AaronAndrews M103 sim. - final simulated background
Texttxt M103_BG_1.txt r1 manage 0.2 K 25 Nov 2016 - 11:06 AaronAndrews M103 sim. - BG parameters
PNGpng M103_BGfinal_1.png r1 manage 421.7 K 25 Nov 2016 - 13:29 AaronAndrews M103 sim. - final background
PNGpng M103_BGmean_1.png r1 manage 49.0 K 25 Nov 2016 - 13:24 AaronAndrews M103 sim. - BG mean
PNGpng M103_BGsd_1.png r1 manage 70.0 K 25 Nov 2016 - 13:24 AaronAndrews M103 sim. - BG standard deviation
PNGpng M103_Background-Median_im.png r1 manage 1698.3 K 25 Nov 2016 - 12:52 LauraBevilacqua  
PNGpng M103_BackgroundOnly_Hist.png r1 manage 192.6 K 25 Nov 2016 - 12:07 LauraBevilacqua  
PNGpng M103_BackgroundStars-Median_im.png r1 manage 354.1 K 25 Nov 2016 - 12:52 LauraBevilacqua  
PNGpng M103_BackgroundStars_Hist.png r1 manage 186.3 K 25 Nov 2016 - 12:07 LauraBevilacqua  
PNGpng M103_Sim_11size_NoBackground.png r1 manage 91.3 K 25 Nov 2016 - 12:07 LauraBevilacqua  
PNGpng M103_Sim_201size_NoBackground.png r1 manage 91.4 K 25 Nov 2016 - 12:07 LauraBevilacqua  
Unknown file formatfits M103_Simtest_noBG.fits r1 manage 12195.0 K 25 Nov 2016 - 11:04 AaronAndrews M103 sim. - stars only
Texttxt M103_Simtest_noBG.txt r1 manage 8.0 K 25 Nov 2016 - 11:06 AaronAndrews M103 sim. - Star parameters
Unknown file formatfits M103_starsBG_1.fits r1 manage 12195.0 K 25 Nov 2016 - 11:04 AaronAndrews M103 sim. - stars+BG
PNGpng M103_starsBG_1_GS.png r1 manage 1312.1 K 25 Nov 2016 - 13:30 AaronAndrews M103 sim - stars + BG greyscale
Texttxt Simulation_test10.py.txt r1 manage 28.8 K 25 Nov 2016 - 11:02 AaronAndrews Simulation program 10 (+ median analysis)
PNGpng StatsPlotsM103SBG.png r1 manage 171.0 K 25 Nov 2016 - 12:12 AnishaVadher Median, sigma and mean plots on simulated M103 with background
PNGpng StatsPlotsSimulatedBG.png r1 manage 295.5 K 25 Nov 2016 - 12:15 AnishaVadher Median, sigma and mean plots on simulated background
PNGpng compare.png r1 manage 119.8 K 25 Nov 2016 - 12:36 AnishaVadher Size of the median filter box as a function of the fitted mean and the fitted standard deviation
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Topic revision: r13 - 25 Nov 2016 - AnishaVadher

 
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