"The dark sky."
Translation:An t-adhar dorcha.
If you mean "Why do they not accept it?", the answer is because it is wrong.
dorch a □ a common alternative form of dorcha
So I have no clue why it has changed. Note that the word is related to Gaelic dearg and English dark. See my post on another question.
If you mean vowels with accents on, here is an answer:
The technical answer is that the accent tells you the vowel is long, but they do not mark it when a Gaelic expert would know it was long anyway (usually because of a double letter after). In practice, people don't seem to have much problem with the ones that aren't marked (so perhaps that is why they are not marked!). So let's look at the ones that are marked:
The accent means it is a 'long vowel'. You quite literally say it for longer, and, as SrGI2aed points out you should practise stretching these much more than feels comfortable in English. You should also listen carefully to the pronunciation of all the words with accents and try to notice the length.
In fact, English speakers are unusually bad at vowel length, and there is a reason for this. Once upon a time, mat and mate sounded much the same, except for vowel length (so these would be written mat and màt in Gaelic), just like bata 'stick' and bàta 'boat'. So you would be used to making the difference clear when you spoke and hearing the difference when listening. But then, due to the Great Vowel Shift all our long vowels changed. That is why it is now easy to tell the difference between mat and mate without paying any attention to vowel length - and that is why we are now so bad at vowel length. D
That's what I would say. I would sometimes use adhar = sky but only when something was in it, as to me it means 'air, atmosphere'. So birds, clouds and airoplanes coult be san adhar 'in the sky', but I would not use it for what you see beyond the atmoshphere. However lots of other people do. There is no doubt that both answers are correct, IMO.
But you do not state if you tried speur and had it rejected. If you did then someone should raise it as 'my answer should be accepted'.