Difference: 20151103MsciPhotometryAnalysisHotPixels (1 vs. 2)

Revision 203 Nov 2015 - ElenaCukanovaite

Line: 1 to 1
 
META TOPICPARENT name="StewartBoogertPhotometry2015"

Detecting hot pixels

  • We had two 1 hour exposure dark frames. One was at an angle and the other pointed upwards.
Line: 6 to 6
 
  • Wrote a for loop program to do that.
  • Wanted to investigate if the hot pixels were clustered for each image.
  • To do that we plotted a histogram of the frequency of hot pixels in x and y coordinates for each image.
Changed:
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  • For the upwards picture 6951 pixels were found.
  • For the image at an angle 5748 pixels were found.
>
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  • For the upwards picture 6951 pixels were found for the threshold of 2000.
  • For the image at an angle 5748 pixels were found for the threshold of 2000.
 
  • In total there are 1560600 pixels.

Histograms for x and y positions

  • x coordinate histograms for upwards and at an angle.
Line: 31 to 31
 
  • For both images the shape of the histogram is similar.
  • There is an unusual spike.
  • At an angle the spike is at 4000 pixel values, whereas when the camera is pointed upwards, the spike appears at 6000 pixel values.
Added:
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Comparing hotness of the two independent 1 hour exposures

  • We wanted to investigate how the hotness changes with the angle of the camera.
  • We had two images, upwards and at an angle.
  • We matched the hot pixels between the two lists.
  • Some pixels were matched more than once, because some pixels had no corresponding hot pixel in the image, this is because the upward image had a lot more hot pixels.
  • The correspond histograms are shown below for different threshold pixel values.
30_bins_30000_thres.png

100_bins_3000_thres.png

  • Due to computing time many different threshold values were used.
  • We could only go down to 3000 pixel values as the threshold.
  • We expected a Gaussian centered on 0, because we expect a symmetric difference with the most common difference being zero, and the difference is less likely.
  • As can be seen, especially at large thresholds the shape deviates from a Gaussian and it is not centered on 0.
  • Some differences are very high.
  • For the threshold of 3000 pixel values, there were 5573 hot pixels for upwards image and 4453 hot pixels in the angle image.
  • It appears that there are always more hot pixels in the upwards image as compared to the image at an angle.
 -- ElenaCukanovaite - 03 Nov 2015

META FILEATTACHMENT attachment="number_of_pixels_x_coordinate_angle.png" attr="" comment="" date="1446557308" name="number_of_pixels_x_coordinate_angle.png" path="number_of_pixels_x_coordinate_angle.png" size="28918" user="zxap014" version="1"
Line: 39 to 55
 
META FILEATTACHMENT attachment="number_of_pixels_y_coordinate_upwards.png" attr="" comment="" date="1446557323" name="number_of_pixels_y_coordinate_upwards.png" path="number_of_pixels_y_coordinate_upwards.png" size="32035" user="zxap014" version="1"
META FILEATTACHMENT attachment="hotness_histogram_upwards.png" attr="" comment="" date="1446558434" name="hotness_histogram_upwards.png" path="hotness_histogram_upwards.png" size="30141" user="zxap014" version="1"
META FILEATTACHMENT attachment="hotness_histogram_angle.png" attr="" comment="" date="1446558439" name="hotness_histogram_angle.png" path="hotness_histogram_angle.png" size="27239" user="zxap014" version="1"
Changed:
<
<
META FILEATTACHMENT attachment="hot_pixels_upwards.txt" attr="" comment="" date="1446561788" name="hot_pixels_upwards.txt" path="hot_pixels_upwards.txt" size="146862" user="zxap014" version="1"
META FILEATTACHMENT attachment="hot_pixels_angle.txt" attr="" comment="" date="1446561793" name="hot_pixels_angle.txt" path="hot_pixels_angle.txt" size="121099" user="zxap014" version="1"
>
>
META FILEATTACHMENT attachment="hot_pixels_upwards.txt" attr="" comment="List of hot pixels. Column 1 is for x coordinates, column 2 is for y coordinates, column 3 is the hotness. This list was generated for the threshold of 2000 pixels." date="1446561788" name="hot_pixels_upwards.txt" path="hot_pixels_upwards.txt" size="146862" user="zxap014" version="1"
META FILEATTACHMENT attachment="hot_pixels_angle.txt" attr="" comment="List of hot pixels. Column 1 is for x coordinates, column 2 is for y coordinates, column 3 is the hotness. This list was generated for the threshold of 2000 pixels." date="1446561793" name="hot_pixels_angle.txt" path="hot_pixels_angle.txt" size="121099" user="zxap014" version="1"
META FILEATTACHMENT attachment="100_bins_3000_thres.png" attr="" comment="" date="1446566172" name="100_bins_3000_thres.png" path="100_bins_3000_thres.png" size="26684" user="zxap014" version="1"
META FILEATTACHMENT attachment="30_bins_30000_thres.png" attr="" comment="" date="1446566181" name="30_bins_30000_thres.png" path="30_bins_30000_thres.png" size="26798" user="zxap014" version="1"

Revision 103 Nov 2015 - ElenaCukanovaite

Line: 1 to 1
Added:
>
>
META TOPICPARENT name="StewartBoogertPhotometry2015"

Detecting hot pixels

  • We had two 1 hour exposure dark frames. One was at an angle and the other pointed upwards.
  • We wanted to find the x and y coordinates of hot pixels and the hotness of those pixels for each image.
  • Wrote a for loop program to do that.
  • Wanted to investigate if the hot pixels were clustered for each image.
  • To do that we plotted a histogram of the frequency of hot pixels in x and y coordinates for each image.
  • For the upwards picture 6951 pixels were found.
  • For the image at an angle 5748 pixels were found.
  • In total there are 1560600 pixels.

Histograms for x and y positions

  • x coordinate histograms for upwards and at an angle.
number_of_pixels_x_coordinate_upwards.png

number_of_pixels_x_coordinate_angle.png

  • y coordinate histograms for upwards and at an angle.
number_of_pixels_y_coordinate_upwards.png

number_of_pixels_y_coordinate_angle.png

  • The plots show where there are more hot pixels. In this case it is at the edges of the CCD.
  • Plots agree for both images.
  • For upwards image there are more hot pixels and it would explain why there are more pixels for a given x or y bin.

Histograms for hotness of pixels

  • The hotness of the hot pixels was plotted as a histrogram for both images.
hotness_histogram_upwards.png

hotness_histogram_angle.png

  • For both images the shape of the histogram is similar.
  • There is an unusual spike.
  • At an angle the spike is at 4000 pixel values, whereas when the camera is pointed upwards, the spike appears at 6000 pixel values.
-- ElenaCukanovaite - 03 Nov 2015

META FILEATTACHMENT attachment="number_of_pixels_x_coordinate_angle.png" attr="" comment="" date="1446557308" name="number_of_pixels_x_coordinate_angle.png" path="number_of_pixels_x_coordinate_angle.png" size="28918" user="zxap014" version="1"
META FILEATTACHMENT attachment="number_of_pixels_x_coordinate_upwards.png" attr="" comment="" date="1446557313" name="number_of_pixels_x_coordinate_upwards.png" path="number_of_pixels_x_coordinate_upwards.png" size="29801" user="zxap014" version="1"
META FILEATTACHMENT attachment="number_of_pixels_y_coordinate_angle.png" attr="" comment="" date="1446557318" name="number_of_pixels_y_coordinate_angle.png" path="number_of_pixels_y_coordinate_angle.png" size="31008" user="zxap014" version="1"
META FILEATTACHMENT attachment="number_of_pixels_y_coordinate_upwards.png" attr="" comment="" date="1446557323" name="number_of_pixels_y_coordinate_upwards.png" path="number_of_pixels_y_coordinate_upwards.png" size="32035" user="zxap014" version="1"
META FILEATTACHMENT attachment="hotness_histogram_upwards.png" attr="" comment="" date="1446558434" name="hotness_histogram_upwards.png" path="hotness_histogram_upwards.png" size="30141" user="zxap014" version="1"
META FILEATTACHMENT attachment="hotness_histogram_angle.png" attr="" comment="" date="1446558439" name="hotness_histogram_angle.png" path="hotness_histogram_angle.png" size="27239" user="zxap014" version="1"
META FILEATTACHMENT attachment="hot_pixels_upwards.txt" attr="" comment="" date="1446561788" name="hot_pixels_upwards.txt" path="hot_pixels_upwards.txt" size="146862" user="zxap014" version="1"
META FILEATTACHMENT attachment="hot_pixels_angle.txt" attr="" comment="" date="1446561793" name="hot_pixels_angle.txt" path="hot_pixels_angle.txt" size="121099" user="zxap014" version="1"
 
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