Those who want big optical performance for terrestrial (and astronomical) observing in a small package should consider the 5" aperture Celestron C5 Schmidt-Cassegrain spotting scope. Despite its long 1250mm focal length (effectively 49"), the C5 is physically only 13.75" long with eyepiece in place (only 11" without eyepiece). This makes it easily transportable.
Its 127mm aperture gathers nearly four and a half times as much light as a 60mm spotting scope (and almost two and a half times that of an 80mm) for truly exceptional low light capability. It has more than twice the resolution of a 60mm scope as well, and more than 50% better resolution than an 80mm.
The C5 has Starbright XLT advanced antireflection multicoatings (the finest optical multicoatings available from any commercial manufacturer) on both sides of its corrector lens and a Starbright XLT multicoated enhanced aluminum mirrors. The very high light transmission of this coatings and mirror package markedly extends your observing time in the low light of early morning and dusk.
The supplied 50x eyepiece has a 53' field at 1000 yards that is well suited for detailed medium and long distance birding and nature studies. The long 22mm eye relief of the eyepiece allows comfortable eyeglass use. Other optional eyepieces are available for powers ranging from 31x to 125x (the highest power routinely usable for long distance birding with this size scope under good seeing conditions, although higher powers are available under superior seeing conditions.) 75x to 90x might be a more reasonable useful maximum power range on an everyday basis.
The C5 has a 6 x 30mm erect image crosshair finderscope mounted on the top of its rear cell to help center the high power main scope on distant objects. The finderscope combines a good 6x magnification with an exceptionally wide 7° field of view (368' at 1000 yards). The supplied straight-through finderscope and comfortable 45° viewing angle eyepiece holder both yield erect and right-reading images (so that printing is correctly oriented and readable). This makes it extremely easy to follow subjects in motion, as their direction of travel is the same whether you are using your unaided eye, the finderscope, or the 50x eyepiece.
The Celestron C5 is a Better View Desired Online BVD "Starred" product - a product considered to be in the same class as the category's "Reference Standard," but which some birders might prefer. Since the Reference Standard in the catadioptric spotting scope category is a $4000+ Questar Birder, that puts the C5 in some very high quality company.
In its review of the C5, BVD Online said, "In the field, at medium powers (40-60X), the C5 provides the kinds of views you have only dreamed about. It is one of the few scopes on the market that actually gives the impression of giving you a better view, brighter, richer, more detailed, at those powers than you get through your binoculars at 8X, and there seems to be no upper limit to the amount of detail you can see at higher powers.
"The C5 resolves finer detail than my test chart shows at 36 feet with the lines very sharply defined. There is little or no sign of the line blurring that results from aberrations in the optical design. Outside, the C5 still resolves the finest lines on my chart at 66 feet, and might go a bit beyond. That translates to a resolution of 0.71 arc seconds, a fifth of an arc second better than theory, and more than twice the resolution of the best refractor that I have tested. You just can't get much better resolution than that!
"If you regularly need extreme high power to reach across a lake or tidal flat, I would have no hesitation in recommending the C5 as your best choice. Even if you are only going to use the scope at moderate powers, you really can not buy a better view at any price."
The C5 easily converts to a very high power 1250mm (25x) f/9.84 telephoto lens by simply adding optional camera adapter #7930 and an optional T-ring. The 32-turn focusing knob at the rear of the scope is extremely precise for critical, but relatively slow, focusing as close as 20'. The multicoated Celestron C5 is a big-performing spotting scope - at a size and price that are not so very big. Because of its high power capabilities, the C5 needs a very substantial tripod for acceptable tremor-free operation.
In addition to having 1/4"-20 thread holes for mounting it on a photo tripod, the dovetail bracket on the underside of the C5 body allows the scope to be mounted on a variety of astronomical mounts (such as the Celestron Advanced Series German equatorial go-to mount). The C5 comes in a soft-side foam-padded carrying case.
