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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.
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- 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.
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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.
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- In total there are 1560600 pixels.
Histograms for x and y positions
- x coordinate histograms for upwards and at an angle.
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- 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.
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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.
- 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.
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| -- 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" |
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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" |
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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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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" |
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