The 10 x 42mm Granite’s field is commendably flat. Images stay in focus from one side of the field to the other. Barrel distortion, the curving of straight lines at the edge of the field, is minimal. There is some minor chromatic aberration at the very edges of the field, but it is unnoticeable during most observing.
Is the Celestron Granite ED mechanically and optically the equal of the most expensive high end/high-power roof prism binoculars? Not quite. But it comes surprisingly close at a fraction the cost.
Features of this binocular . . .
Roof prism optics. Open bridge H-body roof prism design with internal center focus. High quality BaK-4 prisms for unrestricted light transmission.ED glass. ED (Extra-low Dispersion) glass is used in the objective lenses to deliver excellent edge-to-edge sharpness and color correction, while essentially eliminating chromatic aberration during every day use. The eco-friendly glasses used throughout this Celestron Granite binocular are lead and arsenic free.Broadband multicoated optics. Fully coated on all air to glass optical surfaces with multiple layers of ion-deposited broadband antireflection materials for high light transmission and contrast, even in low light.Phase-coated high transmission prisms. The image-erecting roof prisms are made of high quality BaK-4 glass, with high transmission multicoatings to minimize light loss for the brightest possible images. In addition, special phase-correcting coatings are applied to the roof prisms for peak contrast, color fidelity, and resolution. The resulting improvement is easily seen when looking for color and detail in the shadowed areas of a silhouetted or backlit bird.Open bridge magnesium body. The open bridge body design allows the fingers of your hands to wrap naturally around the binocular body for a secure grip in all weather conditions, even when using a single-hand grip. The body is made of magnesium, which is both much lighter than aluminum and more rugged to absorb accidental abuse without flinching.Waterproof and fogproof. Dry nitrogen filled and O-ring sealed to be waterproof and fogproof in all temperature and climate extremes. Designed to operate reliably in rain forests and deserts alike.Armor. Black rubber armor absorbs noise and the bumps and thumps of everyday use and provides a good grip when wet. Thumb recesses and ridges where your fingers naturally fall assure a secure grip.Wide field. The field of view is 6.5° (340’ at 1000 yards), quite good for a 10x binocular.Twist-up eyecups and good eye relief. The eyecups (metal for long life, not flimsy plastic) are rubber-rimmed for comfort. They twist up to block ambient light and increase contrast for those who don’t wear glasses. They retract for eyeglass or sunglass use. Click stops provide three distinct eyecup heights to let you match the individual eyecup height to your eyes. Eye relief is specified at 15mm, although it typically measures a mm or two less due to the recessed position of the eye lens (from where the eye relief is typically measured). This provides only mildly vignetted viewing for sunglass wearers or those who must wear eyeglasses when observing.Eyepiece rainguard and lens covers. A rubber eyepiece rainguard is standard equipment, to keep eyepieces dry in sudden showers. It can be attached to the binocular neckstrap to hang down out of the way to one side when not in use, without danger of its getting lost. Tethered objective lens covers protect the optics during travel or storage. They flip off the optics and hang down under the binocular tubes to stay out of the way when not in use, but can be removed completely if so desired.Close focusing. About two turns of the ribbed rubber focusing knob moves from a good near focus of 8.2’ out to the horizon and beyond. Shallow rubber ribs inset into the metal focus knob make it easy to turn the focus knob, regardless of the weather. An 8.2’ close focus is surprisingly useful for woodland birding.Rotary diopter correction. A continuously variable metal diopter ring on the right eyepiece allows you to match the binocular optics precisely to your individual eyesight for a sharp image.Tripod adaptable. For extended no-hands observing, a protective cover on the front bridge unscrews, revealing a 1/4"-20 thread hole for mounting the Celestron 10 x 42mm Granite on an optional photo tripod using an optional tripod adapter #11107.Standard accessories. A one and a half inch wide neoprene-padded neck strap for comfortable all-day use and a water-shedding lightly padded Cordura-style nylon and vinyl carrying case with a wide woven shoulder strap are standard equipment.Free binocular harness. An unexpected but welcome no-charge bonus is a binocular harness that permits no-hands carrying of the binocular, in addition to taking the strain off your neck by distributing the weight of the binoculars to your shoulders and torso.
A note on our eye relief figures: Quite
often, our eye relief figures will differ from those of the
manufacturer. This is because we measure the “usable” eye relief, while
the manufacturers specify their usually-longer (but technically correct)
“designed” eye relief.
The eye lens of the eyepiece is normally
recessed below the rubber eyeguard or rubber rim of the eyepiece to keep
the lens from being scratched during use. An eyepiece might have a
“designed” eye relief of 15mm (and the eye relief will truly measure
15mm from the eye lens to where the image forms). However, if the eye
lens is recessed 3mm below the eye guard, the Ramsden Disk forms only
12mm above the eyepiece body (the 15mm “designed” eye relief, less the
3mm of eye relief made unusable by having the eye lens recessed into the
body of the eyepiece). This “usable” eye relief of 12mm (measured from
the rolled-down eyeguard – the closest point you can get your eye to the
eye lens – to where the image forms) is the eye relief figure we would
measure and list in this website.
Why is it important to list the “usable” eye relief? For
those people who don’t wear eyeglasses while observing, a few mm
difference between the eye relief they expect from the manufacturer’s
literature and the shorter eye relief they actually get in real life
doesn’t mean a lot. They can simply move a little closer to the eyepiece
to see the full field, and never realize that the eye relief is a
little shorter than they expected. However, some people must wear
eyeglasses while observing, because of severe astigmatism. These
observers can’t move closer to the eyepiece if the eye relief is shorter
than expected because their glasses get in the way. For these people,
the real life “usable” eye relief is more important than the technically
correct but sometimes not fully usable “designed” eye relief. We
measure and list the actual usable eye relief so that people in the real
world can pick the eyepieces that will work best for them.