Aperture photometry New!!!

Prerequisito

AttenzioneGnuplot is needed⚓

Gnuplot is a portable command-line driven graphing utility for Linux

Suggerimento

If you use Ubuntu or Mint click on the link below

Gnuplot

  1. Convert your images in a sequence

  2. when preprocessed images

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    You can even consider making a cosmetic correction in addition to that proposed automatically with the the dark subtraction.

    Menu Image processing/Cosmetic Correction...

  3. Demosaicing (for Bayer-Pattern images only)

    ConsiglioIt is recommended to only work on the green channel, demosaiced with super pixel algorithm.⚓

    Attenzione

    Do not use other algorithms that would introduce artifact due to interpolation.

    Nota

    The red layer is strongly noised by the light pollution and the blue layer by atmospheric refraction.

    Consiglio

    Aperture photometry compares stars of the same image, keeping the green layer is the best choice.

  4. Images registration

    Nota

    Working on an registered images sequence is a better choice

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    Use either One Star Registration or Global Star Alignment in this case check Translation only

  5. Export the sequence

  6. Load the sequence

  7. Select variable star

    1. AttenzioneYou have to make a fairly wide selection,⚓

      It is necessary to check that the largest circle is completely included.

      All parts of the circle outside the selection will be ignored.

  8. Once the selection has been made,

    Attenzione

    check with the statistics option that the maximum is not 65535

    1. Attenzione

      If the value is 65535, the star is saturated.

      The results will be inoperable.

  9. Do a PSF for sequence

    Nota

    A median filter is applied to the selection in order to remove hot pixels that could lead to bad star detection.

  10. Then we look for stars with a close magnitude

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    To help you, when you make the selection, look at the bottom right of the image the value of the FWHM which must be close to the FWHM value of the variable star.

    1. EsempioHere the value is 8.56 for the variable star.⚓

  11. Check with Statistics tool that the selected star is not saturated

    1. Attenzione

      The values given by the statistical tool only concern the open image, not the entire sequence of images.

  12. Do a PSF for sequence

  13. Repeat previous steps for 3 or 4 more stars

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    If a curve of a reference star appears suspicious, click on delete the last curve and choose another star.

  14. In the plot tab select Magnitude

  15. Click on Plot Var

    1. Consiglio

      X axis: Julian Day

      • format: geocentric based on UTC

      Y axis: magnitude difference:

      • Magnitude of the variable - magnitude of the super star.
      • The super star is the star constructed from the stars of reference.