Questar Birder, 90mm, broadband coatings, Zerodur mirror, 40/60x, finder, rapid focus, case

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This Questar Birder with broadband optical coatings and a Zerodur mirror is a “legendary” Questar Field Model specially optimized for birding in extreme climate conditions by the addition of a large aperture wide-field refractor-type finder, faster focusing, high light transmission broadband optical coatings and silver mirrors for the brightest possible images, and a thermally stable Zerodur ceramic mirror. It is the spotting scope everyone turns to when the identification of a distant bird hangs in the balance. The Birder has an ultra-sharp 40x eyepiece that converts to either a 60x eyepiece or a wide-field 8x finderscope at the flip of a lever. Other optional higher-power eyepieces are available, as well.

The large aperture 8x refractor-type finder has a wide 300’ field of view. The finder is built under the barrel of the scope, rigidly and permanently aligned with the main optics and located safely out of the way. The scope’s 40x eyepiece operates at 8x when viewing through the finder. A simple touch on a lever at the rear of the scope instantly switches between the 8x finder and the 40x main optics, so you never have to move your head from one eyepiece to another and chance losing the bird as you do with scopes that have a separate finder. Touch another lever and the magnification instantly increases to 60x. The Birder also includes the 24-turn fast focusing mechanism that’s normally optional with the Field Model. The faster-acting 24-turn focusing is a helpful feature for more quickly tracking moving birds and wildlife. The Birder has quickly-removed soft black plastic dust covers for the objective lens, finderscope lens, and eyepiece.

This broadband-coated Zerodur Birder includes high transmission/low reflection broadband dielectric multicoatings on both sides of its objective lens for a light loss of less than 1/10th of 1% per surface for the brightest possible images. This multicoatings package also includes high reflectivity silver mirror coatings with a protective overcoating of thorium fluoride instead of standard aluminum coatings with a silicon monoxide overcoat. The broadband coatings package gives you a full 22% gain in light transmission and contrast that’s very useful for twilight viewing and photography. The thermally-stable Zerodur ceramic mirror is perfect for critical photographic situations that don’t allow focus changes during wide temperature swings. This is helpful for use in difficult locations such as the Arctic or Sahara, but is usually not needed in the continental United States or Hawaii, as well as in most of Canada. The Zerodur mirror offers no other optical advantage, other than the thermal stability, so this Zerodur version of the Birder would be a case of overkill for most birders. The somewhat less expensive broadband coatings/Pyrex mirror version of the Birder (Questar model #QBB) will be more than adequate for 99% of all birders.

However, the broadband coatings package (either this Zerodur mirror version or the Pyrex mirror version) is not recommended if you live full time on ocean-front property, or spend much of the year birding at the seaside. Constant exposure to salt air can adversely affect the silver mirror coatings. Occasional visits to the shore are not a problem, only extended stays (particularly if the scope is not packed away in its case when not in use). If prolonged exposure to salt air might be in your spotting scope’s future, consider the Birder with standard optical coatings (Questar model #QB), rather than this broadband-coated version. You will lose some light transmission, but will gain a measure of optical coating longevity. Adding a few packets of desiccant (silica gel or similar, available at most camera stores) to the case of any spotting scope to absorb moisture when near large bodies of salt water would be a helpful preventative measure in any event.

All other basic specifications and features of the Field Model remain the same with this Birder – a built-in Barlow lens to increase eyepiece magnification at the flip of a lever, a slide-on metal lens shade, a basic camera coupling set (needs a Questar T-ring), waterproof carrying case, etc.

So, just how good is the basic Field Model that this scope is based on? One of our customers from Nebraska called up shortly after he received his Questar 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!” (The exclamation point is 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 and a high power finderscope to let you locate those distant birds. The supplied standard equipment eyepiece gives you a basic 40x magnification. A built-in 1.5x Barlow lens increases that power to 60x at the touch of your finger on a lever at the rear of the scope. Another lever instantly converts the 40x eyepiece to an 8x finder with a wide 5.7 degree field of view (300’ 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.

For those birders who prefer higher powers, an optional 53x eyepiece is available that provides 80x when the built-in Barlow is used. The 53x eyepiece can be substituted for the standard equipment 40x eyepiece at no extra cost, if the substitution is requested at the time your scope is ordered. The 53x 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. (The standard 40x eyepiece has a good 15mm of eye relief, however.)

Because of its high power and its ability to focus as close as 20’ (although with a very shallow depth of field at that close a distance), the Birder 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 40x magnification, subjects 20 feet away appear the same size as they would if you could get your eye within a mere 6” of them, with a field only 4.6” 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 Birder comes with a quickly-removed heavy black vinyl protective dust cap. Similar caps are provided for the finderscope’s objective lens and eyepiece. 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 Birder 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.

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 58’ 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.

A foam-fitted waterproof hard case is standard equipment.

Ten-year Questar warranty (two-year warranty on the focuser, five years on the broadband coatings).

As the review in Audubon concluded simply, “Questar is superb.” If you want the world’s very best spotting scope, a Questar is it. Period. Case closed.

Magnification is the ability of a telescope to make a small, distant object large enough to examine in detail. If you look at the Moon (250,000 miles away) with a 125 power (125x) telescope, it's essentially the same as looking at it with your bare eyes from 2000 miles away (250,000 ÷ 125 = 2000). The same telescope used terrestrially will make an object one mile away appear to be only 42 feet away (5280 feet ÷ 125 = 42).
The magnification of a telescope is determined by dividing the focal length of the telescope (usually in millimeters) by the focal length of the eyepiece used (again, usually in millimeters; but in all cases by the same unit of measurement used for the telescope focal length). For example, a 2000mm focal length telescope and a 10mm focal length eyepiece will give you a magnification of 200 power (2000 ÷ 10 = 200). The same 2000mm telescope with a 20mm eyepiece will give you 100x (2000 ÷ 20 = 100).
40 & 60x
Field of view 1000 yards:
58' @ 40x
Near Focus:
Eye Relief:
Eye relief is the distance from the last surface of the eye lens of an eyepiece to the plane behind the eyepiece where all the light rays of the exit pupil come to a focus and the circular image is formed, sometimes called the “Ramsden Disk.” This is where your eye should be positioned to see the full field of view of the eyepiece. If you must wear glasses because of astigmatism, you’ll usually need at least 15mm of eye relief or longer if you want to see the full field of view with your glasses on.

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.

15mm @ 40x
Exit Pupil:
The circular image or beam of light formed by the eyepiece of a telescope. To take full advantage of a scope's light-gathering capacity, the diameter of an eyepiece exit pupil should be no larger than the 7mm diameter of your eye's dark-adapted pupil, so that all of the light collected by the telescope enters your eye. (The eyepiece exit pupil diameter is found by dividing the eyepiece focal length by the telescope focal ratio.) Your eye's ability to dilate declines with increasing age (to a dark-adapted pupil of about 5mm by age 50 or so). For those in this age group, eyepieces with exit pupils larger than their eyes can dilate to simply waste their telescope's light-gathering capacity, as some of the scope's light will fall on their iris instead of entering their eye.
2.2mm @ 40x
Twilight Factor:
A number used to compare the effectiveness of binoculars or spotting scopes used in low light. The twilight factor is found by multiplying the size of the objective lens (in mm) by the magnification and then finding the square root of that result. The larger the twilight factor, the more detail you can see in low light. A twilight factor of 17 or better if usually required for reasonable low light use.
59.7 @ 40x
This is the diameter of the light-gathering main mirror or objective lens of a telescope. In general, the larger the aperture, the better the resolution and the fainter the objects you can see.
A binocular or spotting scope whose body is clad in rubber or polyurethane armor is said to be armored. Armor can be applied for looks, a better grip, noise-proofing, etc. An armored body does not guarantee that a binocular or spotting scope is waterproof, although most waterproof optics are armored.
Photographic Focal Length:
The effective focal length of a spotting scope/camera adapter combination when the scope is used as a telephoto lens. The photographic focal length divided by 50 will give you the magnification of the combination compared to your standard camera lens.
Photographic Focal Ratio:
The photographic “speed” of a spotting scope/camera adapter combination when used for photography. The smaller the “f/ratio,” the faster the exposure (to capture birds in motion), or the dimmer the light level in which you can successfully shoot.
10 years
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Questar - Birder Model, 90mm broadband coatings, Zerodur mirror, 40/60x, finder, rapid focus, case

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Questar - Birder Model, 90mm broadband coatings, Zerodur mirror, 40/60x, finder, rapid focus, caseImage showing the control box at the rear of the scope.
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This is it. The broadband-coated/Zerodur mirror Questar Birder is the ultimate spotting scope . . .

. . . our 38th year