A late equaliser in fog-bound Romania prevented Celtic from reaching the last 32 of the Europa League with two games to spare.
Stefan Johansen's stunning strike had Ronny Deila's side ahead after half an hour but Astra equalised thanks to Brazilian William Amorin’s fine finish with 11 minutes remaining. The home side had Vincent Laban sent off for a reckless lunge on Charlie Mulgrew in the closing stages.
Salzburg booked their place in the knock-out stage by thrashing Dinamo Zagreb 5-1 in Croatia and Celtic are well placed to join them from Group D.
The Parkhead club are five points clear of Dinamo with two matches to play - the next of which is against Salzburg in Glasgow on November 27.