Aperture Photometry (Copy)

Aperture photometry is a method used in astronomy to measure the brightness (flux) of a celestial object by summing the light within a defined aperture while subtracting the background contribution. It is widely used for analyzing stars, galaxies, and other point sources in images, especially in FITS format.

Steps in Aperture Photometry

1. Defining the Aperture

   • A circular or elliptical region centered on the object is chosen to include most of the target's flux.

2. Background Estimation

   • A surrounding annular (doughnut-shaped) region is used to estimate the background sky level.

   • The average background flux per pixel is calculated and subtracted from the total flux inside the aperture.

3. Flux Calculation

   • The total flux is obtained by summing the pixel values within the aperture and subtracting the estimated background flux.

4. Magnitude Estimation

   • The measured flux can be converted to an apparent magnitude with a logarithmic scale, with a zero point that determined from the photometry of standard stars.