When the sun is fully eclipsed the sky darkens and the stars appears as if it was night. Obviously, when this happens in the middle of the day, and the process of the moon slowly moving to occlude the sun is clear, then it is no different than dark clouds in the sky.
The question here is if the sun is fully eclipsed following sunset but before Tzes HaChochavim. In this circumstance, the cause of the early darkness is not apparent because the sun in below the horizon. When the stars disappear early they will not reappear again until the following dawn. Night has, by all appearances, to any witnesses observers, fallen early.
Does this early darkness and early appearance of stars meet the halachic requirements of 'Tzes HaChochavim'?
(Please provide sources, pre-500CE, i.e. on the direct authority of Sanhedrin or higher, only.)