Difference: 20151101_MSciSpectrocopyLab (2 vs. 3)

Revision 303 Nov 2015 - JosephBayley

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META TOPICPARENT name="StewartBoogertSpectroscopy2015"
Hot Pixels
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  • Analysed a two dark frames to find locations of hot pixels. 1st Dark frame had a 1 second exposure time at a temperature of 20 degrees. 2nd Dark frame had a second exposure time at a temperature at 5 degrees.
  • As can be seen from both spectrums below, the 2nd dark frame has comparatively less background fluctuations due to the lower temperature.
  • A code was written to print the index of the pixel values which exceed the mean+standard deviation of the 1D array obtained from summing each column of pixels downwards. Pixel values exceeding this limit are considered signicantly above the background.
  • Spectrum of dark frame analysed with spikes indicating hot pixels:
Hotpixels.png
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>		*The background data of a dark frame was plotted at an exposure of 2 s and a temperature of 10deg.
 
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<		3 second dark frame
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  • Background_hot.png:
    Background_hot.png
 
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  • Pixel values exceeding this limit were located at pixel positions 90, 180, 222, 407, 490, 497, 617 along the x axis for the 1st dark frame.
  • Pixel values exceeding this limit were located at positions 90, 222, 407, 617 along x axis for 2nd dark frame - conclude these are hot pixels.
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  • The large spikes in the plot are believed to be 'hot pixels'
  • By finding the standard deviation and mean of the background data, any points that were larger than the standard deviation plus the mean were recorded. This process is repeated for 2 dark frames so that the hot pixels can be determined.
  • For the 1st frame, pixel values exceeding this limit were located at pixel positions 90, 180, 222, 407, 490, 497, 617 along the x axis.
  • For the second frame, pixel values exceeding this limit were located at positions 90, 222, 407, 617 along x axis.
  • We can then conclude that the repeated positions are 'Hot pixels'.
  • The 'hot pixels' were then set to a value of the average of its surrounding pixels. This then gave a plot of:

  • Background_nohot.png:
    Background_nohot.png

  • The background can be seen to be rising in intensity towards one side of the camera. Not sure as to why?
 Finding the best focus distance/camera angle

  • After meeting on 28/10/15, decided to fit a hyperbole to the standard deviation against focus distance plot and a sine function to the standard deviation against camera angle plot - these fits were a much better fit than the parabolas.
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  • Chi square value for focus = 0.00665
  • Chi square value for angle = 0.000382
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  • Focus : $\chi ^2$ = 0.00665
  • Angle : $\chi ^2$ = 0.000382
 
  • Still need to adjust errors - will ask Prof Cowan in own time
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<		Focus.png

Angle.png

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  • Focus_fit.png:
    Focus_fit.png
 
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  • Angle_fit.png:
    Angle_fit.png
 -- AshleaKemp - 02 Nov 2015
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META FILEATTACHMENT attachment="Hotpixels.png" attr="" comment="Dark frame spectrum" date="1446428380" name="Hotpixels.png" path="Hotpixels.png" size="34303" user="zxap013" version="1"
META FILEATTACHMENT attachment="Focus.png" attr="" comment="stdev versus focus" date="1446465546" name="Focus.png" path="Focus.png" size="32705" user="zxap013" version="2"
META FILEATTACHMENT attachment="Angle.png" attr="" comment="stdev versus angle" date="1446465524" name="Angle.png" path="Angle.png" size="34590" user="zxap013" version="2"
META FILEATTACHMENT attachment="Hot.png" attr="" comment="dark frame 2s 5 deg" date="1446429347" name="Hot.png" path="Hot.png" size="36913" user="zxap013" version="1"
META FILEATTACHMENT attachment="g.png" attr="" comment="3 second dark frame" date="1446430040" name="g.png" path="g.png" size="37628" user="zxap013" version="1"
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META FILEATTACHMENT attachment="Hotpixels.png" attr="h" comment="Dark frame spectrum" date="1446428380" name="Hotpixels.png" path="Hotpixels.png" size="34303" user="zxap013" version="1"
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META FILEATTACHMENT attachment="Angle.png" attr="h" comment="stdev versus angle" date="1446465524" name="Angle.png" path="Angle.png" size="34590" user="zxap013" version="2"
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