Manuel López-Ibáñez

This may be a good reference to check: https://link.springer.com/article/10.1007/s10569-021-10033-9#Equ32 Unfortunately this is beyond my knowledge of astrophysics. I cannot get Eq 38 to work with poliastro's propagation.

> I think the problem could be that the force is not changes to km/s^2 in method: Yes, that is another problem fixed by #1389

> Unclear if the problem was fully fixed in #1389? Not fixed: > This seems to solve the error in the eccentricity. However, I still notice a problem with the...

@astrojuanlu Something seems wrong with the checks. Not sure why they fail.

```python from poliastro.twobody.angles import M_to_nu_elliptic, E_to_nu, M_to_E from astropy import units as u %timeit [ M_to_nu_elliptic(M=x * u.deg, ecc=0.1 * u.one) for x in range(0,180)] %timeit [ E_to_nu(M_to_E(M=x * u.deg,...

> * Add a short sentence to the docstring pointing out that parabolic and hyperbolic versions are not provided on purpose, and linking to #1013 I didn't provide them because...

> I wonder if the performance gain also happens if the caller is also jitted? I would assume that if numba does inlining (or when numba does inlining), then there...

> * Move a function to a different module, like `poliastro.util`, to make it clear that this is a convenience function. Sure. Should the core version also move to poliastro.core.util...

> These metrics are a bit outdated, but I would propose to implement some of the quality indicators from: > Coello Coello and Falcon-Cardona,: _Convergence and Diversity Analysis of Indicator-based...

@jonpsy It seems to me that you are right. You can probably remove delta1 completely. Maybe send a pull request?