The Serbian international, signed from Sporting Gijon for £2.3 million, got off the mark in his seventh appearance for the Scottish champions as they stayed unbeaten at the top of Group D after three rounds of fixtures.
Scepovic had missed several chances before he put Celtic ahead but manager Deila insisted he was always confident the 23-year-old would come good.
“That’s why I kept him on the pitch,” said Deila. “I know what a goalscorer he is. He really wants to perform for this club.
“He was very tense before the game. It is a big relief for him and it’s not the last goal we will see from him.
“He will get more confident now. I see him in training, how good he is on the ball and how he scores goals. I’m very happy for him.
“He had two big chances before he scored. But I know what he has. He is smelling chances all the time and he got a good goal eventually.”
On a fraught evening for Deila’s side, they were again grateful to goalkeeper Craig Gordon for providing the platform to achieve another positive Europa League result.
Outstanding in both the 2-2 draw away to Salzburg on matchday one and then the 1-0 win at home to Dinamo Zagreb, Gordon made some important saves again last night while the scoreline was still goalless.
Celtic made the breakthrough in the 73rd minute through Scepovic’s first goal for the club and doubled it five minutes later when Stefan Johansen pounced on an error by Astra ‘keeper Silvio Lung.
Gabriel Enache pulled one back for Astra in the 81st minute but Celtic held on for the victory which leaves them in a positive position halfway through the Group D programme, level on points at the top with Salzburg who were 4-2 winners at home to Zagreb last night, with Brazilian striker Alan grabbing a hat-trick.
“When we went 2-0 ahead, I hoped the game was over,” added Deila. “But Astra came back again which was disappointing.
“We had more chances than them in second half but we could have been behind in the first half with some stupid mistakes we made.
“We gave Astra chances with some bad passing. We were too slow, had too many touches on ball and too little movement in front of the ball. Not enough players were in the box for crosses. That was better in the second half.
“We want to get better, we want to be quicker that we were tonight.
“But if we didn’t have the possession we had, it would have been worse. We had eight chances which is not so bad.
“If we can win our next game against Astra in Romania [on 6 November], it could be enough to see us through. It will be if Salzburg also beat Zagreb again in their next match. But I never take anything for granted. We still have two away games left in the group and we need to be at our best if we are going to go through.”
Astra coach Oleg Protasov was entitled to feel frustrated his team left Celtic Park with nothing to show for their efforts but remained philosophical.
“I don’t think Celtic were lucky, although we had more good chances to score,” he said. “Maybe a draw would have been the right result.
“I haven’t been with my team long, I’m just trying to organise things. I think my players did their jobs well and could possibly have got a better result.
“We have some very good midfielders to create chances. If I had some better strikers, we would have done better tonight.
“There is no pressure on us in the home game against Celtic now and we will try to win it.”