Histogram of the trial image

The trial images is shown below.


The histogram is done over the entire trial image and is divided into 50 bins. The bin with the most entries represents the background. The rest of the bins are populated by stars.


3D plots and Gaussian fits

Two selected stars from the trial image are shown below.


Attached images show the 3D plots of selected stars from the trial image (orange colouring). Gaussian fits (blue colouring) to selected stars are also attached. Unfortunately, the fits are not good. Although one of the stars is close to saturation and therefore the badness of its fit could be due to that, another star that is not saturated is badly fit as well.





Detection of stars in a given image

Attached are cropped images of the trial image with the background signal removed. First the mode of the image is found, then its standard deviation. The background is then defined as any value that falls within x*the standard deviation of the mode. The two images attached show instances for x=3 and x=15. This can be thought of as the detection threshold.



HR diagram of the Beehive Cluster

Attached is a HR diagram for the Beehive Cluster. It was generated using the SIMBAD catalogue. The stars were found within 1.7 degrees of RA= 8h 40.1m, Dec= +19 59'.


  1. There are various ways to find a target using SIMBAD. Easiest is finding the target using its RA and DEC. To do this choose the 'Coordinate Query'.
  2. Type in your coordinates and define the radius of the region around your target that you want to explore.
  3. 'Submit query' will give you all of the found targets in your selected region.
  4. To save the data you will have to go to 'Output Option' tab and choose the output format. This tab also allows you to choose the information you want to get about your targets.
  5. I would recommend ASCII (aligned, without separator) type and only ticking the boxes of the data you need. This will make the data file less cluttered and easier to work with. Also, I would at first decrease the target radius thereby decreasing the amount of stars SIMBAD gives, making the data file even cleaner and easier to work with. I would write the code for that file first and then when that code is working perfectly, I would download all my target star data and run the complete data file through the code.
-- ElenaCukanovaite - 13 Oct 2015
Topic attachments
I Attachment History Action Size Date Who Comment
PNGpng TrialImage.png r1 manage 48.7 K 20 Oct 2015 - 15:50 DavidHadden Supplied trial image
PNGpng TrialImageCrop.png r1 manage 61.7 K 20 Oct 2015 - 15:50 DavidHadden Cropped version of supplied trial image showing two brightest stars
PNGpng fifteen_std.png r1 manage 47.2 K 13 Oct 2015 - 11:42 ElenaCukanovaite Cropped part of the trial image. White space represents the background removed. The background is defined within 15 standard deviation of the mode value.
PNGpng gaussian_fit.png r1 manage 142.0 K 13 Oct 2015 - 16:27 ElenaCukanovaite Gaussian fit to a saturated star in the trial image.
PNGpng gaussian_fit_unsaturated.png r1 manage 190.5 K 13 Oct 2015 - 16:34 ElenaCukanovaite A Gaussian fit to an unsaturated star in the trial image.
PNGpng good_gaussian_fit.png r1 manage 167.7 K 13 Oct 2015 - 16:29 ElenaCukanovaite A gaussian fit to some sample data.
PNGpng histogram_fifty_bins.png r1 manage 29.7 K 13 Oct 2015 - 11:37 ElenaCukanovaite Preliminary histogram of a trial image
PNGpng hr_beehive.png r1 manage 84.5 K 13 Oct 2015 - 20:02 ElenaCukanovaite HRdiagram for the beehive cluster using SIMBAD data.
PNGpng star.png r1 manage 290.4 K 13 Oct 2015 - 11:39 ElenaCukanovaite A star from the trial image
PNGpng stars.png r1 manage 181.9 K 13 Oct 2015 - 11:40 ElenaCukanovaite Two of the stars in the trial image
PNGpng three_sts.png r1 manage 88.2 K 13 Oct 2015 - 11:41 ElenaCukanovaite Cropped part of the trial image. White space represents the background removed. The background is defined within 3 standard deviation of the mode value.
Edit | Attach | Watch | Print version | History: r10 < r9 < r8 < r7 < r6 | Backlinks | Raw View | Raw edit | More topic actions

Physics WebpagesRHUL WebpagesCampus Connect • Royal Holloway, University of London, Egham, Surrey TW20 0EX; Tel/Fax +44 (0)1784 434455/437520

Topic revision: r10 - 20 Oct 2015 - DavidHadden

This site is powered by the TWiki collaboration platform Powered by PerlCopyright © 2008-2024 by the contributing authors. All material on this collaboration platform is the property of the contributing authors.
Ideas, requests, problems regarding RHUL Physics Department TWiki? Send feedback