# 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:
<
<
• For the upwards picture 6951 pixels were found.
• For the image at an angle 5748 pixels were found.
>
>
• 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.
>
>

### 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.

• 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" 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" 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" 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" 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" 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" 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
>
>
 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.

• y coordinate histograms for upwards and at an angle.

• 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.

• 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" 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" 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" 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" 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" 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" 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" 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"

Copyright © 2008-2021 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