Difference: Meeting2401 (1 vs. 4)

Revision 424 Jan 2019 - AriannaSaba

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META TOPICPARENT name="StewartBoogertPhotometry2018"
JC: I have investigated the aperture size using a test image of the Double cluster. I chose an appropriate test frame such that there were at least two stars 'close together'. This was required in order to establish a reasonable upper limit on aperture size as it was observed larger apertures increase the likelyhood of including more than one star in any given aperture. pixel_sum_v_hw_double_cluster.png - It is observed that for all stars, the sum of pixel values within each aperture reaches an almost constant value after subtracting the median background value per pixel. This background value was calculated individually for each star using the immediate pixels surrounding each aperture. These boxes used to calculate the star-specific background value may include other stars themsevles however this will not dramatically effect calculations in most cases as it is the medial pixel value that is used as a background value. column_hist_double_cluster.pngrow_hist_double_cluster.pngHere are both the row and column pixel sum projections with the overall median background level indicated in orange. star_locate_double_cluster.png -And here is a plot of the detected star apertures shown in red. The blue box indicated the square area used.
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  Schermata_2019-01-24_alle_16.20.58.png
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In addition, I investigated further some old part of the project, like the dark analysis (analysis of dark frames), the background analysis (how the mean value of the background changes while moving in the x and y direction) and how to compute b_ij (which I still need to perfectionate).

As I feel like we should not go back and forth over the different topics of the project, I will avoid to put any information relative to that here, as it might be confusing later. If necessary and requested I will be happy to discuss it next time.

 
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Revision 324 Jan 2019 - AriannaSaba

Line: 1 to 1
 
META TOPICPARENT name="StewartBoogertPhotometry2018"
JC: I have investigated the aperture size using a test image of the Double cluster. I chose an appropriate test frame such that there were at least two stars 'close together'. This was required in order to establish a reasonable upper limit on aperture size as it was observed larger apertures increase the likelyhood of including more than one star in any given aperture. pixel_sum_v_hw_double_cluster.png - It is observed that for all stars, the sum of pixel values within each aperture reaches an almost constant value after subtracting the median background value per pixel. This background value was calculated individually for each star using the immediate pixels surrounding each aperture. These boxes used to calculate the star-specific background value may include other stars themsevles however this will not dramatically effect calculations in most cases as it is the medial pixel value that is used as a background value. column_hist_double_cluster.pngrow_hist_double_cluster.pngHere are both the row and column pixel sum projections with the overall median background level indicated in orange. star_locate_double_cluster.png -And here is a plot of the detected star apertures shown in red. The blue box indicated the square area used.
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Arianna:

I continued to develop the star finder algorithm, in particular calculating the baricenter of each star, the flux and the magnitude.

Here I attach a plot of the stars found by the algorithm; their baricenter is identified with a dot.

I also calculated the error in the baricenter. However, it cannot be seen because too small. I also attach a zoom in to prove that error bars are actually there.

The values for each quantity are listed in this table.

To do:

  • calculate the error in the flux and in the magnitude.
  • plot the measured magnitude vs the published value.

stars.png

Schermata_2019-01-24_alle_16.35.00.png

Schermata_2019-01-24_alle_16.20.58.png

 
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Revision 224 Jan 2019 - JacobChambers

Line: 1 to 1
 
META TOPICPARENT name="StewartBoogertPhotometry2018"
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JC: I have investigated the aperture size using a test image of the Double cluster. I chose an appropriate test frame such that there were at least two stars 'close together'. This was required in order to establish a reasonable upper limit on aperture size as it was observed larger apertures increase the likelyhood of including more than one star in any given aperture. pixel_sum_v_hw_double_cluster.png - It is observed that for all stars, the sum of pixel values within each aperture reaches an almost constant value after subtracting the median background value per pixel. This background value was calculated individually for each star using the immediate pixels surrounding each aperture. These boxes used to calculate the star-specific background value may include other stars themsevles however this will not dramatically effect calculations in most cases as it is the medial pixel value that is used as a background value.
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JC: I have investigated the aperture size using a test image of the Double cluster. I chose an appropriate test frame such that there were at least two stars 'close together'. This was required in order to establish a reasonable upper limit on aperture size as it was observed larger apertures increase the likelyhood of including more than one star in any given aperture. pixel_sum_v_hw_double_cluster.png - It is observed that for all stars, the sum of pixel values within each aperture reaches an almost constant value after subtracting the median background value per pixel. This background value was calculated individually for each star using the immediate pixels surrounding each aperture. These boxes used to calculate the star-specific background value may include other stars themsevles however this will not dramatically effect calculations in most cases as it is the medial pixel value that is used as a background value. column_hist_double_cluster.pngrow_hist_double_cluster.pngHere are both the row and column pixel sum projections with the overall median background level indicated in orange. star_locate_double_cluster.png -And here is a plot of the detected star apertures shown in red. The blue box indicated the square area used.
 
META FILEATTACHMENT attachment="pixel_sum_v_hw_double_cluster.png" attr="" comment="" date="1548321685" name="pixel_sum_v_hw_double_cluster.png" path="pixel_sum_v_hw_double_cluster.png" size="97375" user="zbvd104" version="1"
META FILEATTACHMENT attachment="back_plot_double_cluster.png" attr="" comment="" date="1548321709" name="back_plot_double_cluster.png" path="back_plot_double_cluster.png" size="21152" user="zbvd104" version="1"

Revision 124 Jan 2019 - JacobChambers

Line: 1 to 1
Added:
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META TOPICPARENT name="StewartBoogertPhotometry2018"
JC: I have investigated the aperture size using a test image of the Double cluster. I chose an appropriate test frame such that there were at least two stars 'close together'. This was required in order to establish a reasonable upper limit on aperture size as it was observed larger apertures increase the likelyhood of including more than one star in any given aperture. pixel_sum_v_hw_double_cluster.png - It is observed that for all stars, the sum of pixel values within each aperture reaches an almost constant value after subtracting the median background value per pixel. This background value was calculated individually for each star using the immediate pixels surrounding each aperture. These boxes used to calculate the star-specific background value may include other stars themsevles however this will not dramatically effect calculations in most cases as it is the medial pixel value that is used as a background value.

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META FILEATTACHMENT attachment="back_plot_double_cluster.png" attr="" comment="" date="1548321709" name="back_plot_double_cluster.png" path="back_plot_double_cluster.png" size="21152" user="zbvd104" version="1"
META FILEATTACHMENT attachment="column_hist_double_cluster.png" attr="" comment="" date="1548321726" name="column_hist_double_cluster.png" path="column_hist_double_cluster.png" size="41573" user="zbvd104" version="1"
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