Minimum separation of stars

  • Need threshold for position matching of stars between frames.
  • For each star in true visual data for Double Cluster (), determined minimum separation to adjacent star. Constructed histogram:
  • minDistHistogram_vTrue.png
  • Mode: 5.1634
  • FWHM: 5.6489
  • Smallest minimum distance: 0.2643
Preliminary HR for true data

  • Ran preliminary analysis on Double cluster images from observation 2, made HR diagram.
  • Magnitude calculated using equation:
 \begin{equation} m = -2.5 \log_{10}\left ( \frac{ADU_{total} \times gain / t_{exp}}{F_{vega}} \right )+c \end{equation}

Filter Flux at m=0 (photons s^-1 m^-2)
B 4260*1.51e7/0.22
V 3640*1.51e7/0.16
R 3080*1.51e7/0.23
  • (Note: flux sometimes measured in units of Jy, 'jansky', where 1Jy=1.51e7 (dLambda/Lambda)^-1. This is shown above. Source:http://www.astro.utoronto.ca/~patton/astro/mags.html)
  • For best match to real data, calculated offset c for both B and V filters:
    • B: c=-8.14300827674
    • V: c=-8.28699220211
  • HR diagram (cutoff applied to real data):
  • RealHR_cutoff.png
  • Plotted fraction of stars found out of the number of expected stars for different star finding thresholds
  • The threshold is set as the mode+maxSigma*n where n isn't necessarily an integer, values of n are shown on the x axis of the plot below
  • fractionStars.png
-- AaronAndrews - 23 Jan 2017
Topic attachments
I Attachment History Action Size Date Who Comment
PNGpng RealHR_cutoff.png r1 manage 95.0 K 24 Jan 2017 - 22:48 AaronAndrews Double cluster HR, real data compared to true, cutoff
PNGpng RealHR_full.png r1 manage 133.4 K 24 Jan 2017 - 22:48 AaronAndrews Double cluster HR, real data compared to true, full
PNGpng fractionStars.png r2 r1 manage 30.3 K 25 Jan 2017 - 10:40 LauraBevilacqua Fraction of stars found, using the star finder, for different thresholds
PNGpng minDistHistogram_vCand.png r1 manage 25.7 K 23 Jan 2017 - 23:02 AaronAndrews histogram of minimum distances, real candidate V data
PNGpng minDistHistogram_vTrue.png r2 r1 manage 28.5 K 23 Jan 2017 - 23:15 AaronAndrews minimum separation histogram, true v data
Edit | Attach | Watch | Print version | History: r3 < r2 < r1 | 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: r3 - 25 Jan 2017 - LauraBevilacqua

 
This site is powered by the TWiki collaboration platform Powered by PerlCopyright © 2008-2021 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