Thanks

Use the ELLIPSE command [with the PELLIPSE System Variable set to 0].  If you want to do it with the electronic equivalent of manual drafting techniques, using something like a compass, you can't make it a true elliptical shape, because the curvature of an ellipse is of constantly changing radius, so there's nowhere to put the compass point.  If PELLIPSE is set to 1, it makes an approximation with 16 arc segments, which is pretty close [and was the only way, and that System Variable did not exist, in early versions before the ELLIPSE command made a real elliptical shape].

Before AutoCAD R13 of year 1995 ! the R 12 release had effectively not so precise ellispses and as R12 was the first software coming in my work company this lead to a funny exchange between an old but reliable engineer with "only" his polish method calculator and an young with no experience contractor unable to draw "perfect" ellipses with the R12, only given the OK with the R13 release.

Dery, up to what level of perfection do you want to go ?

I once complained about the unprecise helix drawn by AutoCAD and a german guy gave me a program to draw it correctly because the AutoCAD one was 200 mm apart ( only at the extremities ) for a 10 m radius.