The Cobblers kicked off attacking the River End goal, but it was at the other end where the first goal attempt came after eight minutes when Ryan Jarvis headed wide from Craig Fleming's right-wing cross.
A quarter-of-an-hour into the game, Jim Brennan's low left-foot drive brought a good save from Mark Bunn. The keeper did equally well to hold onto a deflected shot from Adam Drury.
He was then at full stretch to turn over a dipping shot from Ian Henderson.
Huckerby was bundled over by Gavin Johnson and got up to take the spot kick himself. Bunn guessed the right way but Huckerby's firm right-foot shot beat the keeper low to his left.
Scott McGleish came close to an equaliser, but his overhead shot was headed off the line by Andrew Hughes.
Five minutes into the second half Huckerby was felled by Gavin Johnson who was booked. Two minutes later he was followed into the book by Petr Mikolanda for persistent fouling.
Huckerby could take no further part in the game and limped off to be replaced by Ashton. Bunn was smartly down to save Brennan's free-kick and a snap-shot from Hughes.
However, he could do nothing to prevent Ashton making it 2-0 in the 78th minute, when he got his right foot to Brennan's diagonal right-wing cross and the ball flew past the out stretched fingertips of Bunn's right hand to nestle in the top corner of the net.
The Cobblers huffed and puffed, but the City defence stood firm with centre-half Gary Doherty outstanding.