Difference: 20151208MSciPhotometryAnalysisOb1part4 (9 vs. 10)

Revision 1008 Dec 2015 - ElenaCukanovaite

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META TOPICPARENT name="StewartBoogertPhotometry2015"

Mode Substraction

  • We substracted the split mode image from the original image.
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  • Having imposed this limit, several suspect stars were removed from the image.
  • In addition to the above, we also increased the threshold for an objec to considered a star to amount of pixels = 20.
  • Below can be seen the results.
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final_removal.png
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final_removal.png
 
  • Where the red dots now show stars which were removed from the image.
  • This appears to remove several problem candidates, such as those seen below.
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removed_edge.png
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removed_edge.png
 
  • Here you can see that stars appearing half on the frame, which we would not be able to fit properly, will not be counted now, as they do not appear circular.
  • Below it can be seen that several apparent 'hot pixels' have been removed, however a concern is objects which could be stars (such as the object on the right) may also be removed.
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removed_ratio_1_3.png
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removed_ratio_1_3.png
 

Standard deviations of stars

  • We known that the standard deviations of the stars in the image should be the same in x and y directions.
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  %ENDLATEX%
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b_r.png
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b_r.png
 
  • The above graph is an example of a fitted star for summed rows. This appeared to be a good fit, although a slight skew appears to exist in this data, so we modified our fitting function in order to account for this, by changing the y term in the formula to a polynomial in y. (visible skew in y, not so much in x, left it for now).
%BEGINLATEX%
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  %ENDLATEX%
  • This was then performed, and a comparison can be seen below:
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skewed_example.png
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skewed_example.png
 
  • From this, one can see that this seems to follow the points better, but not perfectly, and highlights the skew of the curve.
  • However, not all fits were so successful.

Fitting problems

  • A recurring issue seen in our projections is the presence of more than 1 star in the cropped image, which obviously does not fit properly.
  • This is currently a major issue for such scenarios, which must be resolved.
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bad.png
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bad.png
  -- ElenaCukanovaite - 08 Dec 2015
 
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