calculate_noise#
- stellarphot.photometry.photometry.calculate_noise(camera=None, counts=0.0, sky_per_pix=0.0, aperture_area=0, annulus_area=0, exposure=0, include_digitization=False)[source]#
Computes the noise in a photometric measurement.
This function computes the noise (in units of electrons) in a photometric measurement using the revised CCD equation from Collins et al (2017) AJ, 153, 77 who based their expression on the one originally proposed for SNR by Merline, W. J., & Howell, S. B. 1995, Experimental Astronomy, 6, 163.
The equation is:
\[\sigma = \sqrt{G \cdot N_C + A \cdot \left(1 + \frac{A}{B}\right)\cdot \left[ G\cdot S + D \cdot t + R^2 + (0.289 G)^2\right]}\]where \(\sigma\) is the noise, \(G\) is the gain, \(N_C\) is the source counts (which is photon/electron counts divided by gain), \(A\) is the aperture area in pixels, \(B\) is the annulus area in pixels, \(S\) is the sky counts per pixel, \(D\) is the dark current in electrons per second, \(R\) is the read noise in electrons per pixel per read, and \(t\) is exposure time in seconds.
Note: The \((0.289 G)^2\) term is “digitization noise” and is optional.
- Parameters:
- camera
stellarphot.Camera The camera object that contains the gain, read noise and dark current of the CCD.
- countsfloat, optional
Counts of the source.
- sky_per_pixfloat, optional
Sky per pixel in counts per pixel.
- aperture_areaint, optional
Area of the aperture in pixels.
- annulus_areaint, optional
Area of the annulus in pixels.
- exposureint, optional
Exposure time in seconds.
- include_digitizationbool, optional
Whether to include the digitization noise. Defaults to False.
- camera
- Returns:
- noisefloat
The noise in the photometric measurement in electrons.