The 24-year-old Serbian striker has failed to convince since signing from Sporting Gijon for a reported £2.3million in the summer and had not found the net in six appearances.
He was only playing because John Guidetti once again had to drop out as he was not registered in time for the group stages of the competition following his loan move from Manchester City.
As the Scottish champions struggled against the visitors, Scepovic missed two sitters with his head early in the second half but he made amends when he headed in an Anthony Stokes free-kick in the 73rd minute.
Midfielder Stefan Johansen made it 2-0, only for Gabriel Enache to pull a goal back to ensure a nervy ending, but it ended with Celtic three points better off ahead of the trip to Romania for the return game on November 6.
Asked if he felt Scepovic was never going to score against Astra, Deila said: "No
That's why I kept him on the pitch.
"I saw the chances were coming
Stefan had two big chances before he scored but I am happy for him that he got the goal.
"I know what a goal scorer he is and he got the goal in the end.
"He really wants to perform for this club.
"He was very tense before the game, I could see it in him and there was a big relief, of course, when he scored the goal and it is not the last goal we will see from him.
"We know what he has
He is always in front of goal and smelling chances.
"He will go on to score more goals.
"You can imagine what you feel when you score your first goal.
"He will become more confident as well
I see in training that he is good on the ball and scores goals, so I am very happy for him."
Celtic are level with Salzburg at the top of the section with seven points, following the Austrian side's 4-2 home win over Dinamo Zagreb.
Deila believes 10 points could be enough to qualify through to the knockout stages but insists there is still a long way to go.
He said: "It could be that 10 points are enough
But I am taking nothing for granted
It is a lot of hard work in Europe, with two away games to go and there are some very even games.
"So we need to be at our best if we are to go through.
"We gave Astra some chances in the first half with some bad passes and some stupid mistakes
We were too slow and took too many touches on the ball.
"When we got to 2-0 I hoped the game was over but they came back again and that was disappointing
But in the end we won the game and in the second half we had more chances."
Astra manager Oleg Protasov thought his side deserved a draw and looked to make amends in the return game.
He said: "We maybe had more chances to score but a draw was maybe the right result for both teams.
"My team tried to do their best but I would like to say my players did well and of course we would have liked a better result.
"We will try to beat them in Romania
There is no pressure on us so why not?"
Source : PA
Source: PA