Hot Pixels

  • 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:

3 second dark frame

  • 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.
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.
  • Chi square value for focus = 0.00665
  • Chi square value for angle = 0.000382
  • Still need to adjust errors - will ask Prof Cowan in own time


-- AshleaKemp - 02 Nov 2015

Topic attachments
I Attachment History Action Size Date Who Comment
PNGpng Angle.png r1 manage 36.8 K 02 Nov 2015 - 01:48 AshleaKemp stdev against camera angle
PNGpng Focus.png r1 manage 37.3 K 02 Nov 2015 - 01:47 AshleaKemp Stdev against focus distance
PNGpng Hot.png r1 manage 36.0 K 02 Nov 2015 - 01:55 AshleaKemp dark frame 2s 5 deg
PNGpng Hotpixels.png r1 manage 33.5 K 02 Nov 2015 - 01:39 AshleaKemp Dark frame spectrum
PNGpng g.png r1 manage 36.7 K 02 Nov 2015 - 02:07 AshleaKemp 3 second dark frame
Edit | Attach | Watch | Print version | History: r5 | r4 < r3 < r2 < r1 | Backlinks | Raw View | Raw edit | More topic actions...

Physics WebpagesRHUL WebpagesCampus Connect • Royal Holloway, University of London, Egham, Surrey TW20 0EX; Tel/Fax +44 (0)1784 434455/437520

Topic revision: r1 - 02 Nov 2015 - AshleaKemp

  • Edit
  • Attach
This site is powered by the TWiki collaboration platform Powered by PerlCopyright © 2008-2023 by the contributing authors. All material on this collaboration platform is the property of the contributing authors.
Ideas, requests, problems regarding RHUL Physics Department TWiki? Send feedback