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Aperture photometry on a synthetic star

What you are seeing: a synthetic star (Moffat PSF) sits on a sky background with Poisson + read noise. Move the aperture and annulus radii to see how the recovered flux compares to the true flux. Too-small aperture undercounts the star; too-large aperture is contaminated by sky noise.

Figure 1. Synthetic CCD image; circles mark aperture (cyan) and sky annulus (orange).
aperture r6.0
sky r_in / r_out14.0
FWHM (px)2.5
F_true8000
sky / pixel100

WHAT TO TRY

  • Vary each control and watch the rail readouts respond.
  • Compare the diagnostic plot against the live scene.