1. This first thing to know about crossbow sights, is understanding their function, which is, all crossbow sighting systems give you a point of aim on any target thus increasing the accuracy of the crossbow.
2. The second thing to know in crossbow sights, is that all crossbow sighting systems compensate arrow drop or the (arrows trajectory).
3. The third thing to know in crossbow sights, is that a arrow constantly drops once leaving the crossbow, the arc that it drops in, is the arrows trajectory.
Telescopic Sights / Crossbow Scopes:
Telescopic sights consist of a tube and crosswire sight or crosshair mounted internally and the tube is mounted on the crossbow. Telescopic sights are magnified to make targets appear closer aiding in more precise shot placement within crossbow range.
Crossbow telescopic sights generally improves a crossbow hunters efforts in gaining the true accuracy potential of their crossbow by adding some magnification to the sight picture. With a scoped crossbow, sighting game is easier, quicker, and very precise simply because everything appears larger and closer do to magnification.
Crossbow hunters with less than perfect vision will find they are aided by the use of magnification usually 1 1/2x - 4x fixed power are good choices. A heavy duplex reticle is a good choice on crossbow scopes because they are much easier to see.
The crossbow scope should have it's parallax adjusted to around 35 - 50 yards as this is where most game animals within crossbow distance will be. A wide field of view is a good choice as this will aid in quicker target acquisition.
Note: When buying rings and or mounts for your crossbow be sure of the size of the clamp mount as to whether it is standard weaver or 3/8" dovetail such as a rimfire scope.
All Barnett crossbows and cheaper taiwan manufacture Barnett knock-offs use 3/8" dovetail mounting.
Note: Bushnell makes a good Rimfire Riflescope that the parallax is adjusted for 50 yards that is a 1" tube x 32mm for good light gathering capabilities and comes with the rings that will bolt right up to the Barnett crossbows for around $50.00.
Trajectory Compensating and Range Finding Reticle.
The trajectory / range-finding reticle is an excellent choice as well once you understand how simplistic this system is. Range-finding feature is simplistic as the average white-tailed deer is approximately 36" from brisket to rump, you simply move the scope up and down till the deer fits between the heavy stadia wires and you have the deer ranged then you simply select the crosshair that is that range hold dead on and shoot.
The dot sight really has an advantage in extremely low light conditions as the aiming point is illuminated, the disadvantage is in really bright light the dot can almost be rendered useless as the brightness washes out the lit sight. This type of sight has another disadvantage as well, the battery powering the sight might just go dead at the most critical time.
Trajectory Compensating Dot Sight.
The latest innovation from truglo for crossbow hunters is their holograghic dot sight that allows you to select your crossbow arrow speed to space the dots for trajectory compensation correctly at given yardages. Non-magnified, parallax corrected at 30 yards.
Peep and Pin Sights:
The peep and pin sight is the most common crossbow sight and they are quite comparable to the sights found on most hand bows. The real advantage of these sights is in foul weather, rain, snow, there are no glass lenses to worry about keeping dry and clear. The disadvantage with this sight is if your eyes are having a hard time of focusing such as when you get older you can not get a sharp clear sight picture rendering this sight useless.