Questar Field Model, 90mm, broadband coatings, Zerodur mirror, 53/80x, case

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With all due respect to the other spotting scopes shown on this site, there can only be one "best spotting scope in the world." This Questar Field Model is it . . .
Our Product #: QFBZ
Questar Product #: 10310

Product Description

With all due respect to the other spotting scopes shown on this site, there can only be one "best spotting scope in the world." This Questar Field Model with Broadband coatings and a Zerodur mirror is it. Its resolution is truly remarkable, exceeding the theoretical limits for a 3.5" aperture scope. While optical theory predicts 0.33" resolution at a distance of half a mile, a Questar can routinely resolve much thinner bicycle spokes at the same distance, and show you leaf stems at a distance of one mile!

One of our customers from Nebraska called up shortly after he received his Field Model to say his scope clearly showed the power line into his neighbor's house. We didn't think that was all that impressive - until he told us his neighbor lived three miles away! As a review in Audubon magazine noted, "Brighter than reality, the Questar has unbelievably sharp resolution and an extremely flat field. It shows every feather from a half-mile away!" (Exclamation point theirs.)

A Questar has no astigmatism or chromatic aberration - no optical problems of any kind - to detract from your enjoyment. The Audubon review added, "the Field Model is unrivalled as a catadioptric spotting scope. It sets the highest standards for both optical performance and convenience of use."

A review in Cornell University's Living Bird magazine said, "The legendary Questar. There's no question that for the right application this is a fantastic scope."

And just what is the right application? According to the Living Bird review, "there are times when the Questar is indispensable. During the World Series of Birding, the Lab team spied a white blob on an old water tower. Rick put his trusty Bushnell Spacemaster on it at 22x - still a white blob. Kevin tried the Kowa TSN-4 at 60x and saw a white blob that might be a large bird. Finally Todd trained the Questar on it, flipped to 80x, and got a crystal-clear image of a roosting barn owl."

What is the right application? It is any birding challenge where you need absolutely razor-sharp views of distant birds. The supplied standard equipment eyepiece gives you a basic 53x magnification. A built-in Barlow lens increases that power to 80x at the touch of your finger on a lever at the rear of the scope. Another lever instantly converts the 53x eyepiece to a 4x finder with an exceptionally wide 12 degree field of view (630' at 1000 yards). You never risk losing your subject as you move your eye from finder to eyepiece, because finder and eyepiece are one and the same. (Both provide erect but reversed mirror images.)

For those birders who prefer lower powers and a wider field for close-in birding, an optional 40x eyepiece is available that provides 60x when the built-in Barlow is used. With the optional 40x eyepiece in the eyepiece holder, the 4x finderscope magnification drops to 3x, but with an even wider field of view (14 degrees, which is a very wide 735' at 1000 yards). The 40x eyepiece can be substituted for the standard equipment 53x eyepiece at no extra cost, if the substitution is requested at the time your scope is ordered. The 40x eyepiece is also available for separate sale, to give you a total of four separate magnifications from only two eyepieces (using the scope's built-in Barlow lens to increase the power of each eyepiece). A rolldown rubber eyecup is provided on all eyepieces for eyeglass use, although eye relief is relatively limited at higher powers.

Because of its high power and its ability to focus as close as 8' (although with a very shallow depth of field at that close a distance), the Field Model is a marvelous long distance microscope for close-up studies of subjects that are too small or too dangerous or too fragile to examine at close hand - ant hills, bee hives, spider webs, etc. At its standard 53x magnification, subjects 10 feet away appear the same size as they would if you could get your eye within a mere 2.2" of them, with a field only 1.8" wide filling your eyepiece! Imagine your views of gape-mouthed chicks being fed in nearby nests, hummers at feeders, and more!

The black and satin-finished aluminum Field Model comes with a 3/16" thick machined thread-on metal protective dust cap. A slide-on metal lens shade improves both visual and photographic contrast. Other standard equipment includes a camera coupling set that lets you use the Field Model as a razor-sharp 1400mm (28x) f/16 telephoto lens by adding an optional Questar brand P-thread T-ring to fit your particular camera body.

The Field Model has extremely precise 50-turn knob focusing. (We Questar owners soon learn to roll the side of our finger along the side of the focusing knob to speed up focus changes, rather than turn, turn, turn with our fingertips.) Faster-acting 24-turn focusing is available as a factory-installed option for more quickly tracking moving birds and wildlife (although at the cost of increasing the close focus distance to 25' from the standard 8').

An optional roof prism image erector, #6351, is available to allow straight-through viewing (from inside a car being used as a mobile blind, for example, using an optional car window mount). There is a loss of field when the image erector is used (from 54' down to 47' with the 40x eyepiece), the lever that changes from finder to a high power view is disabled, and you can only change powers by changing eyepieces, as the Barlow and finder optics are no longer in the optical path.

This broadband coated version has high transmission/low reflection broadband multicoatings on its objective lens, rather than the standard Field Model's single layer magnesium fluoride antireflection lens coatings. In addition, the mirrors are coated with high reflectivity silver, rather than the aluminum coatings of the standard Field Model. Compared to the standard #QF Field Model, this broadband multicoated version gives you a full 22% higher light transmission and increased contrast that's very useful for twilight viewing and photography. Broadband coatings are not recommended for those who live full time at the seashore, however, as a constant exposure to salt air can cause the silver mirror coatings to deteriorate. Occasional exposure to salt sea air on vacations or field trips is not a problem.

In addition, a thermally-stable Zerodur ceramic mirror is used in place of the standard model's Pyrex mirror for critical photographic situations that don't allow focus changes during wide temperature swings. (If the temperature differential between indoors and outdoors is 30 degrees to 40 degrees Fahrenheit or more, occasional minor refocusing will be required with the standard Field Model as its Pyrex mirror gradually cools down to reach the outdoor air temperature.) A Zerodur mirror eliminates such minor refocusing in the Arctic or Sahara, but is usually not needed in the continental United States or Hawaii, as well as in most of Canada.

A foam-fitted waterproof hard case is standard equipment.

The Field Model has a ten-year Questar warranty (with a two-year warranty on the focuser mechanism and a five-year warranty on the broadband coatings).

As the review in Audubon concluded simply, "Questar is superb." If you want the world's very best spotting scope, this Questar Field Model with broadband coatings and a Zerodur mirror is it. Period. Case closed.

Tech Details

Aperture 3.5"
Armored No
Exit Pupil 1.7mm @ 53x
Eye Relief 8mm
Field of view 1000 yards 46' @ 53x
Length 11"
Magnification 53/80x
Near Focus 8'
Photographic Focal Length 1400mm
Photographic Focal Ratio f/16
Twilight Factor 68.7 @ 53x
Warranty 10 years


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Supplied Accessories

  • High transmission/low reflection broadband multicoatings
  • Low expansion Zerodur ceramic mirror
  • Eyepiece
  • Built-in 1.5x Barlow and 4x finder
  • Lens shade
  • Camera adapter
  • Dust covers
  • Hard case