Translation:They did not see the stars yesterday because it was cloudy.
Ní fhaca siad na réaltaí inné mar ní raibh sé dorcha. Chonaic mé na réaltaí aréir.
Could 'réaltaí' also be used when describing things like movie stars, sport stars, etc...?
Usually, the negative form of the past tense is formed with níor, but feic is one of the exceptions (see also the tips and notes section in 'Verbs: Past 1').
Thus, the negative past form of feic uses ní instead of níor : Ní fhaca... In the same vein, the question past form of feic uses an instead of ar : An bhfaca...?
[I'm not a native or even a fluent Irish speaker, so feel free to correct any errors on my part.]