A scope is a device which can be attached to any ranged weapon. It works like an enchantment, though anyone can apply it to their weapon. Unfortunately, as mentioned above no enchantments have been found which can be applied to ranged weapons, aside from the occasional "Oh, look at me, how fancy, I don't need to use arrows" epic bow. And, sadder still, no enchanters have proven able (or willing) to apply such an enchantment to any other weapon. More's the pity. At any rate, only one scope can be attached to a weapon at a time, nor can they be removed. Applying a scope to a weapon will destroy any existing scope. The resulting bonuses applied to the weapon will be enjoyed by its owner (as applicable) so long as they have it equipped. All scopes can be used by laypersons unskilled in Engineering, so Engineers are able (and well advised) to sell or trade them to others.
Learning: Scoping Out the Trainers.
First we'll discuss the scopes you can learn from a trainer or purchase from a supplier. These are, of course, the most convenient scopes to learn. Some of them are more powerful than you might find out in the wilds, but always keep an eye peeled to trainers: better to know how, and never need, to make something. First you'll learn the Crude Scope from a trainer, quite early in your career. The lenses in the thing aren't too powerful, but at the level you'll be using one, every bit counts! Making the Crude Scope requires a Copper Tube, a Malachite, and a Handful of Copper Bolts. As you become more skilled, you'll learn the Standard Scope, also from a trainer. The Standard Scope, as you see, is slightly more refined than the Crude, but is still a fairly minor power magnification. Creating a Standard Scope requires only a Copper Tube and a Moss Agate for refraction. The next scope you'll learn easily is the Accurate Scope, a slight upgrade in magnification from Standard. Making an Accurate Scope requires a Bronze Tube, a Jade, and a Citrine. The next scope up, the schematic for which is sold by two vendors, is the Deadly Scope. The magnification here is a little increased over the previous models, as you see. Making one requires a Mithril Tube, a pair of Aquamarine, and two Thick Leather. The finest scope available from a trainer or vendor is the Adamantite Scope, providing a noticeable improvement in power magnification. The Adamantite Scope requires eight Adamantite Bars and two Golden Draenite, both quite easy to come by for a skilled picksman in Outland.
Finding: Scoping Out the Competition.
Once you've cut your teeth on a couple of the trainer/vendor scopes, you'll likely want to test your skill (and perhaps your aim) with some scopes more challenging to even learn, let alone make. As you travel the roads and dungeons of Azeroth and Outland alike, you might find some even more refined optical instruments you can learn. The first such scope is the Sniper Scope, whose schematic can be found in a wide range of places (including underwater, fishers!) The Sniper Scope requires a Mithril Tube, a Star Ruby, and a pair of Truesilver Bars.
A little harder to find, and deeper in the ground, too, is the schematic for Biznicks 247x128 Accurascope. This schematic is found in Molten Core, deeper than many care to go,.and is held solely by the lords of that place. The Biznicks requires two each Lava Core and Essence of Earth, four Delicate Arcanite Converters, six Dark Iron Bars, and a Thorium Tube. As you see from the plans, the Biznicks adds to the accuracy, rather than the damage, of the weapon.
Back on the surface, but on another planet, is the schematic for the Khorium Scope, held by the Sunfury Bowmen of Netherstorm. The Khorium Scope continues the progression of damage augmentation, which might not be preferable for those already looking through the Biznicks scope. The Khorium Scope requires a Hardened Adamantite Tube, four Khorium Bars, and two Dawnstones.
The most powerful scope available to us tinkers is the Stabilized Eternium Scope. The schematic for this device can be found on the corpse of Attumen the Huntsman, in the stable of Karazhan. He does not drop the schematic often, and engineers are reminded that Karazhan can only be entered once per week, and that only with a small raid group. Chief Engineer Geargrinder is difficult to engage in conversation on the topic after a year of attempts. Among the things he's known to say of the Stabilized Eternium Scope are words questioning how much hunting anyone gets done in a stable, likening horses in a stable to fish in a barrel, and then degenerating into highly unlikely speculation as to both the likely species and certain profession of Attumen's parents and entire matrilineal heritage. After that, Chief Engineer Geargrinder's commentary lapses into Gnomish profanity, Tauren drinking songs, and, lastly, quiet weeping about "another man's scope" and "shame of a generation."
That notwithstanding, the Stabilized Eternium Scope can be made with the mere expenditure of two Hardened Adamantite Tubes, six Felsteel Stabilizers, and two Stars of Elune. The critical strike rating applied is quite impressive, and noticeable.
Selling: Scoping Out the Market.
A common complaint of the Engineer is that we have little we can market to the common folk. What we can make to sell requires, in many cases, that the user be able to make it in order to use it. Scopes are a marked departure from that norm, however. They are in many cases easy to learn and cheap to make. They can be used by anyone, and therefore can move quite swiftly through the auction houses. The scope is less limited in its appeal than most of our devices. Healers have little use for explosives, but a scope can be used by anyone who wields a gun. Not just hunters, but also Warriors and Rogues, will often be interested in your optical enhancements. Those who only use their ranged weapon once or twice per fight might not be willing to spend a great deal, but those who rely on their ranged weapon entirely might pay through the nose horns to possess one.
As you learn various scopes, peruse your local auction house. With the rarer schematics, particularly the Biznicks and the Stabilized Eternium, you might want to make only one and see how they sell. Crafters of those scopes are rare, but those who can afford them might be rarer still. Remember hardly anyone will need two scopes of the same kind, so always sell your scopes separately.
Cleaning Up Shop: Scoped Out of Metaphors.
As is always the case, it is better to know how to make something you never need to make, than to need to make something and never know how to make it. Pass up no opportunity to learn. Chief Engineer Geargrinder has been lamenting the impossibility of raiding Molten Core since the Dark Portal reopened, and may never learn the Biznicks (additional weeping commences). Hoof and Horn recommends seeking out all schemata, particularly those which can be passed on through gift or commerce. Scopes are high on the list of marketable items, and are also often good to practice Engineering with anyway. Devices which are cheap yet challenging to produce are always welcome as an Engineer learns. This concludes the lecture on scopes.