I just got a Truglo Opti-speed BDC crossbow scope from Opticsplanet.com. I order this because the CenterPoint scope that cam with my Xbow wasn't very good in low light.
This scope has an illuminated reticle and has small crosshairs from 20 to 100 yards. (Not that I'd ever shoot game at that distance). It's pretty unique how it works. You can adjust the magnification as you would any variable scope but once sighted in you leave the power (speed) at that magnification. The power ring is marked for velocity and not magnification. If you have access to a chronograph you get the average speed for your set up and turn the power ring to that setting. You sight in at 20 yards which is the center of the reticle. You then move the target out to 30 or 40 yards and shoot a group and adjust the power ring accordingly. (if you're shooting low gradually turn the ring to a slower speed until you're hitting center). You can adjust any left to right with the scope's L-R turret. After shooting at 20 and 40 yards I went out to 50 yards and found that I was just a bit low so I turned the speed down a tiny bit. Its a nice scope and the illumination is really nice especially in low light or overcast conditions.