$100/nl Check/fold turn?

[FrogMouth]

Villian is 10/2/.8 over a large sample. I felt sick betting that turn.

Full Tilt Poker - No Limit Hold'em Cash Game - $0.50/$1 Blinds - 9 Players - (LegoPoker Hand History Converter)

SB: $100.00
BB: $83.25
UTG: $33.85
UTG+1: $83.45
MP1: $57.90
MP2: $55.15
MP3: $54.95
Hero (CO): $126.00
BTN: $98.50

Preflop: Hero is dealt J[img]/images/graemlins/club.gif[/img] A[img]/images/graemlins/heart.gif[/img] (9 Players)
2 folds, MP1 calls $1.00, 2 folds, <font color="red">Hero raises to $5.00</font>, BTN calls $5.00, 2 folds, MP1 calls $4.00

Flop: ($16.50) 3[img]/images/graemlins/club.gif[/img] 5[img]/images/graemlins/club.gif[/img] A[img]/images/graemlins/club.gif[/img] (3 Players)
MP1 checks, <font color="red">Hero bets $8.00</font>, BTN calls $8.00, MP1 folds

Turn: ($32.50) A[img]/images/graemlins/spade.gif[/img] (2 Players)
<font color="red">Hero bets $20.00</font>, <font color="red">BTN raises to $40.00</font>, Hero??