Version 0.99.8-1 Tutorial

Hello, I recently came across the Tutorials which have been released with the latest version of Siril. Thank you very much to the authors. I regard these as impressive, quite informative work and well written for astrophotography beginners (like me).

Concerning the section Image analysis - Dynamic PSF tool I have two questions, seeking advice:
a) What is the meaning of parameters B and A (math. formula)?
b) RMSE stands for root mean squared error - but error of what?

Appreciating your answers.


  • B — Average local background.
  • A — Amplitude, which is the maximum value of the fitted PSF, and also the function’s value at the centroid coordinates.

This is the error of the fit computation. Indeed, the assumption is that the star is a 2D-Gaussian. We fit the star on this model, and RMSE is the error of the fit.

Thank you. - And the volume under the Gaussian bell corresponds to the brightness of the star, its mag?

Yes, indeed.