Difference: 20160120MSciPhotometryAnalysisOb1part6 (1 vs. 2)

Revision 220 Jan 2016 - ElenaCukanovaite

Line: 1 to 1
 
META TOPICPARENT name="StewartBoogertPhotometry2015"

Mode vs. Median Background

  • The problem with using the mode is that if a number does not appear more than once then the mode just takes the first number in the list.
  • Therefore, a median seems more practical.
Changed:
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  • Below is the mode and median background for splitting of 30x30:
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  • Below is the mode and median background for splitting of 30x30 and 15x15:

mode_30.png median_30.png
mode_15.png median_15.png
  • Because of the reason outlined above we shall use median instead of mode.

Generated star field

  • From simple curve_fit fitting we sampled the parameters $a$, $\rho$, $\sigma_x$ and $\sigma_y$ for the Gaussian for each randomly positioned star:
  \begin{equation} f(x,y,\mu_x,\mu_y,\sigma_x,\sigma_y,\rho,a,d) = \frac{a}{2\pi\sigma_x\sigma_y\sqrt{(1-\rho^2)}} exp\Bigg\{-\frac{1}{2(1-\rho^2)}\Bigg[\bigg(\frac{x-\mu_x}{\sigma_x}\bigg)^2 + \bigg(\frac{y-\mu_y}{\sigma_y}\bigg)^2 -2\rho\bigg(\frac{x-\mu_x}{\sigma_x}\bigg)\bigg(\frac{y-\mu_y}{\sigma_y}\bigg)\Bigg]\Bigg\}  \end{equation}
  • Generated 64 stars.
  • For each randomly generated star position, a Gaussian was generated with the given centers and randomly choisen parameters from fitting images of Location 1 in focus filter (exposure time: 10 seconds).
  • The resulting Gaussian for one star was calculated over the entire image. This was done for all the stars.
  • A background of Poissonian distributed random variables with mean 160 pixel values was also added.
  • Each pixel was then treated such that its pixel value up to this point was taken as the mean of a Poissonian distribution. A random Poissonian variables was then generated with that mean and this was set as the pixel value for each given pixels.
 -- ElenaCukanovaite - 20 Jan 2016
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Revision 120 Jan 2016 - ElenaCukanovaite

Line: 1 to 1
Added:
>
>
META TOPICPARENT name="StewartBoogertPhotometry2015"

Mode vs. Median Background

  • The problem with using the mode is that if a number does not appear more than once then the mode just takes the first number in the list.
  • Therefore, a median seems more practical.
  • Below is the mode and median background for splitting of 30x30:
-- ElenaCukanovaite - 20 Jan 2016
 
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