Hot Pixels

*The background data of a dark frame was plotted at an exposure of 2 s and a temperature of 10deg.

  • Background_hot.png:

  • 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:

  • 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.
  • Focus : $\chi ^2$ = 0.00665
  • Angle : $\chi ^2$ = 0.000382
  • Still need to adjust errors - will ask Prof Cowan in own time
  • Focus_fit.png:

  • Angle_fit.png:
Mapping grating micrometer position to wavelength

  • Initiall two plot were made of cadmiums spectrum at 3.5 mm and 4.0 mm,
  • 3.5_4.0_pixel.png:

  • The pixel distance between the same peak in each frame was found to be 277.
  • By then finding the initial plot in nm, the pixel distance between the same peak could be subtracted to get the correct value as shown below:

  • 3.5_4.0_wavelength.png:
  • By then applying this across the all of the frames of the spectrum, the spectrum for cadmium was obtained, however the values are not quite correct:
  • Cadmium_spectrum.png:
-- AshleaKemp - 02 Nov 2015
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Topic revision: r5 - 03 Nov 2016 - JamesAngthopo

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