Improvements

  • Following on from last weeks meeting, it was suggested the colourmaps used were not overly clear.
  • A version with better contrast has been chosen, and an example is seen below, with the old version, for comparison purposes.
alpha_persei_visual_colour_map_comparison.png
  • Next the issue of over anti-aliased pixels in imshow was addressed.
  • Using the interpolation = 'nearest' option, future imshow images should display proper pixels, as seen below.
interpolation_comparison.png

Accounting for Dark Frames

  • In order to accurately analyse the stars, the background caused by the camera needs to be removed.
  • To do this, a dark frame was scaled down and taken away from the image seen above.
  • An improved image can be seen below, with much of the noisy background regions reduced considerably.
comparison_minus_dark.png

New algorithm for finding stars

  • Used algorithm as showed here.
  • We impleted some arbitrary threshold.
  • We set signal to 1 and background to 0.
  • We impleted the algorithm and unfortunately it has a similar problem to the previous algorithm.
found_stars_600_pe.png

zoom_600_pe.png

super_zoom_600_pe.png

  • It thinks that points not touching diagonally are stars.
  • At the threshold of 1000 photoelectrons we have the following:
found_stars_1000_pe.png
  • We implented a crude to find the centers of each star. We only need it as an initial parameter that we will feed to our Gaussian to estimate a much better center position.
  • We found the centers in the following way:
  1. We had the x and y coordinates of all the pixels of each star.
  2. We summed all x and all y for each star and then divided the sums by the amount of x and y coordinates we had.
  3. This we used as our centers.

Better background determination

  • Split each image into 4 quadrants such that:
l1_quadrants_copy.png

l2_copy.png

  • Found the following modes:
Location 1:
Filter Exposure Time (s) Mode in Quadrant 1 (photoelectrons $\rm{s}^{-1}$) Mode in Quadrant 2 (photoelectrons $\rm{s}^{-1}$) Mode in Quadrant 3 (photoelectrons $\rm{s}^{-1}$) Mode in Quadrant 4 (photoelectrons $\rm{s}^{-1}$)
Focus 10 47.32 46.84 47.80 46.84
Focus 10 47.08 46.37 47.56 46.61
Focus 10 46.61 45.65 46.84 45.89
Focus 10 47.56 47.08 48.28 47.08
Focus 10 47.80 47.32 48.52 47.56
Focus 10 47.56 46.84 48.04 47.08
Focus 10 48.52 47.56 49.00 48.04
Focus 10 47.56 46.61 47.80 46.61
Focus 10 47.80 46.84 48.28 47.08
Focus 10 48.04 47.32 48.76 47.56
Blue 90 5.31 5.20 5.36 5.26
Blue 90 5.39 5.28 5.44 5.31
Blue 90 5.34 5.20 5.36 5.26
Green 40 12.85 12.61 12.97 12.68
Green 40 12.97 12.67 13.03 12.73
Green 40 12.61 12.31 12.67 12.43
Red 40 14.10 13.86 14.16 13.86
Red 40 14.04 13.80 14.04 13.86
Red 40 13.92 13.68 13.98 13.80

Location 2:

Filter Exposure Time (s) Mode in Quadrant 1 (photoelectrons $\rm{s}^{-1}$) Mode in Quadrant 2 (photoelectrons $\rm{s}^{-1}$) Mode in Quadrant 3 (photoelectrons $\rm{s}^{-1}$) Mode in Quadrant 4 (photoelectrons $\rm{s}^{-1}$)
Focus 60 24.54 24.06 24.74 24.18
Focus 60 23.46 22.86 23.58 23.10
Focus 60 22.98 22.47 23.14 22.78
Green 120 7.19 7.03 7.27 7.11
Green 120 7.13 6.91 7.15 6.99
Green 120 7.03 6.83 7.09 6.93
Red 120 8.40 8.25 8.46 8.31
Red 120 8.37 8.21 8.38 8.25
Red 120 7.97 7.75 8.01 7.85

-- DavidHadden - 24 Nov 2015

24.537334
Topic attachments
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PNGpng alpha_persei_2_visual.png manage 684.8 K 24 Nov 2015 - 14:36 DavidHadden  
PNGpng alpha_persei_2_visual_newcmap.png manage 1130.0 K 24 Nov 2015 - 11:45 DavidHadden  
PNGpng alpha_persei_visual_colour_map_comparison.png manage 797.8 K 24 Nov 2015 - 15:15 DavidHadden  
PNGpng comparison_minus_dark.png manage 785.7 K 24 Nov 2015 - 11:45 DavidHadden  
PNGpng found_stars_1000_pe.png manage 36.0 K 24 Nov 2015 - 15:03 ElenaCukanovaite  
PNGpng found_stars_250.png manage 54.2 K 24 Nov 2015 - 14:49 ElenaCukanovaite  
PNGpng found_stars_500.png manage 34.5 K 24 Nov 2015 - 14:50 ElenaCukanovaite  
PNGpng found_stars_600_pe.png manage 53.8 K 24 Nov 2015 - 15:03 ElenaCukanovaite  
PNGpng interpolation_comparison.png manage 186.1 K 24 Nov 2015 - 15:22 DavidHadden  
PNGpng l1_quadrants_copy.png manage 969.8 K 24 Nov 2015 - 19:47 ElenaCukanovaite  
PNGpng l2_copy.png manage 866.1 K 24 Nov 2015 - 19:48 ElenaCukanovaite  
PNGpng super_zoom_250.png manage 53.6 K 24 Nov 2015 - 14:50 ElenaCukanovaite  
PNGpng super_zoom_600_pe.png manage 34.4 K 24 Nov 2015 - 15:03 ElenaCukanovaite  
PNGpng zoom_250.png manage 58.7 K 24 Nov 2015 - 14:49 ElenaCukanovaite  
PNGpng zoom_600_pe.png manage 35.1 K 24 Nov 2015 - 15:03 ElenaCukanovaite  

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Topic revision: r6 - 24 Nov 2015 - ElenaCukanovaite

 
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