Difference: 20151117MSciPhotometryAnalysisOb1 (5 vs. 6)

Revision 617 Nov 2015 - ElenaCukanovaite

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META TOPICPARENT name="StewartBoogertPhotometry2015"

Images

  • We chose the Alpha Persei cluster (Cr 39) to look at, but as it is a large cluster, we took images of two different sections of it, example images of which can be seen below in the visual range.
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  1. Threshold: Found the mode over the entire image, set threshold as described above.
  2. Image Scanning: Wrote a loop which runs over each element in the image, and compares the pixel value to its 8 nearest neighbours. If the central pixel has a larger pixel value than its neighbours, we define this as the centre of the star, and note the x and y coordinates.
  • This was performed on one of the location 1 visual images for a equal to 5 and 10, see figures below for comparison overlays showing the original image and the identified points.
Changed:
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whole_5std.png
  • When $a=5$ we observe detections around the brightest star. This is not accurate and a zoomed in version can be seen below.
star_ring_5std.png
  • It appears as if there is a luminous ring around the star and is separated from the star.
  • At 10 standard deviation threshold the following is seen.
whole_10std.png
  • So now we have x and y positions of each star which depend on the threshold value.
 -- DavidHadden - 17 Nov 2015

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