diff --git a/docs/source/frequently_asked_questions.rst b/docs/source/frequently_asked_questions.rst index 2cc82761..7c247205 100644 --- a/docs/source/frequently_asked_questions.rst +++ b/docs/source/frequently_asked_questions.rst @@ -1,27 +1,32 @@ FAQs - Frequently asked questions ================================= -| **Q:** How do I know what order to put the parameter values in the pytorch - tensor which gets passed to the simulator? -| **A:** If you are using any ``Module``` object (so a simulator), then you can + +**Q:** How do I know what order to put the parameter values in the pytorch tensor which gets passed to the simulator? +----------- + +**A:** If you are using any ``Module``` object (so a simulator), then you can get the parameters using ``print(simulator)``. The order of the dynamical parameters (top to bottom) corresponds to the order you should use in your parameter value tensor. Note that you can ignore the static parameters. -| **Q:** Why can I put the lens redshift at higher values than the source - redshift or to negative values for some parametric models? -| **A:** We can calculate everything for those profiles with reduced deflection + +**Q:** Why can I put the lens redshift at higher values than the source redshift or to negative values for some parametric models? +----------- + +**A:** We can calculate everything for those profiles with reduced deflection angles where the redshifts do not actually play into the calculation. If you use a profile defined by the lens mass, like a NFW lens, or a Multiplane lens then it does matter that the redshifts make sense and you will very likely get errors for those. Similarly, if you call the ``lens.physical_deflection_angle`` you will encounter errors. -| **Q:** I do (multiplane-)lensing with pixelated convergence using the - pixelated kappa map of a parametric profile. The lensing effect differs from - directly using the parametric lens. Why is the lensing effect different? -| **A:** Since you do pixelated convergence your mass is binned in pixels in a - finite field of view (FOV) so you are missing some mass. At the limit of - infinite resolution and infinite FOV the pixelated profile gives you the - parametric profile. If the difference is above your error tolerance then you - have to increase the resolution and/or FOV of your pixelated convergence map. - Especially for SIE or EPL profiles (which go to infinity density in the - center, and have infinite mass outside any FOV) you will miss infinite mass - when pixelating. + +**Q:** I do (multiplane-)lensing with pixelated convergence using the pixelated kappa map of a parametric profile. The lensing effect differs from directly using the parametric lens. Why is the lensing effect different? +----------- + +**A:** Since you do pixelated convergence your mass is binned in pixels in a +finite field of view (FOV) so you are missing some mass. At the limit of +infinite resolution and infinite FOV the pixelated profile gives you the +parametric profile. If the difference is above your error tolerance then you +have to increase the resolution and/or FOV of your pixelated convergence map. +Especially for SIE or EPL profiles (which go to infinity density in the +center, and have infinite mass outside any FOV) you will miss infinite mass +when pixelating.