Questar 3.5" Standard, Magnesium fluoride coatings


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Optical theory says that a Questar should not be able to resolve lunar craterlets and rilles under 1.3 arc seconds across - yet there are countless Questar owners and Questar photos that prove optical theory wrong . . .
Our Product #: Q3
Questar Product #: 10114
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Product Description

In 1950, Questar introduced the first truly portable, lightweight, 3.5" astronomical telescope. Regarded as the finest personal telescope in the world, the 3.5" Questar Standard Maksutov-Cassegrain was legendary for its resolution, flatness of field, and contrast. While today's 3.5" Questar outwardly appears virtually identical to the 1950 original, natural evolution and new technologies have improved even its legendary performance. Today, as in 1950, Questar once again sets the highest standard for optical performance in a truly portable personal telescope, with integrated features that are unavailable with other telescopes.

What is it about a Questar that makes it the best?

Simply this: a fanatical devotion to hand-crafted accuracy.

Hundreds of hours of painstaking, skilled effort and the finest materials available go into producing this optical and mechanical masterpiece. As a Rolls-Royce is to automobiles, so is a Questar to telescopes - the very finest hand-crafted optical performance that money can buy.

What are costly options with other scopes - a glass solar filter, a premium Barlow lens, two premium eyepieces - are all standard with a 3.5" Questar. Also standard are amenities that are simply unavailable on other scopes - a glass solar filter for the finder, an accurate star chart on the self-storing dewcap that slides forward to reveal a useful map of the Moon on the optical tube itself, and a velvet-lined carrying case.

The 3.5" Questar is a complete telescope in a seven pound package. Remove it from its luggage-quality Naugahyde case (or optional leather case), attach the tabletop tripod legs stored in a pocket in the door of the carry case, place it on a table, and you have all the user-friendly controls of a great observatory scope at your fingertips.

Unscrew the dust cap, and you can begin to appreciate the attention to detail lavished on a Questar - for the dust cap is not flimsy press-fit plastic, but solid machined aluminum that threads into the barrel to afford absolute protection to the optics.

Look into the Questar's premium 24mm Brandon eyepiece and you're looking into a 4x finder with an exceptionally wide 12° field. A finger touch on a convenient lever at the rear of the scope changes the finder into a 53x telescope for observing the Moon, nebulas, and star clusters. Touch a second lever and a built-in Dakin Barlow instantly increases that eyepiece power to 80x for closer observing. Exchange the 24mm eyepiece for the supplied 16mm Brandon eyepiece and you extend the power range still further, to 80x and 120x. And optional higher and lower power eyepieces are available, for magnifications as low as 40x and as high as 320x. For observing comfort, a rare thing with many scopes, the eyepiece tilts from side to side to the most convenient observing position.

Observe through a Questar, and you'll appreciate the attention to detail even more. The gearless 25:1 ratio slow motion controls operate with a smoothness and freedom from backlash unmatched by any other amateur telescope. The drive gear diameter is fully half the length of the telescope itself, for tracking precision that must be experienced to be believed. No tiny levers need be thrown to disengage the drive for manual operation, as a butter-smooth internal clutch made from micro-rolled discs of stainless steel lets you move the telescope at will. The large setting circles are not merely painted on, but are engraved and then paint-filled, to remain visible even after years of use. 'Jewel-like precision' may be an overworked term, but it's the only one that does justice to a Questar.

Plug a Questar into a 110 volt 60 Hz household AC outlet and its built-in drive smoothly tracks the Moon, planets, star clusters, galaxies, and a host of other deep space objects across the heavens for you. During the day, the Questar will also track the Sun, allowing you to observe sunspot patterns. You'll do it in complete safety, as standard equipment glass solar filters provide complete protection against the Sun's fierce radiation for both your eye and your telescope.

An optional Powerguide III DC drive system and drive corrector will power the Questar drive motor for up to 50 hours from a single 9 volt transistor radio battery, freeing you forever from the need to stay near an AC outlet to observe the skies. Pushbuttons on the quartz-controlled Powerguide III hand control allow single axis guided astrophotography with drive corrections at 1.4x and 10x the sidereal rate. Dual axis drive correction is possible by adding an optional declination motor. Other buttons control a built-in map light and the brightness of an optional illuminated reticle guiding eyepiece, and select either a lunar or sidereal drive rate. Another button selects northern or southern hemisphere operation, allowing you to use the Questar anywhere in the world without having to worry about finding the proper power frequency or voltage, or the right kind of AC plug. The Powerguide III hand control stores neatly into a pocket in the door of the carrying case when not in use. With a Powerguide III, the Questar is truly a use-anywhere/use-anytime telescope!

High transmission/low reflectivity magnesium fluoride coatings on both sides of the BK7 corrector lens are standard on a Questar. An additional option of broadband dielectric multicoatings to the corrector lens during manufacture (which also includes a change of mirror coatings from aluminum to silver) is also available. This option gives you 22% greater light transmission for deep space viewing, and higher lunar and planetary contrast. (Broadband coatings are not recommended if you live by the seaside, as the silver mirror coatings can be adversely affected by constant exposure to salt air.)

A thermally stable Zerodur ceramic mirror is available as an option to the Questar's standard Pyrex mirror for situations involving large temperature swings. As with any Pyrex mirror telescope, if the difference in temperature between indoors and outdoors is 30 degrees or more Fahrenheit when a Questar is taken outside, minor refocusing will be required as its mirror contracts while cooling down to the outdoor air temperature. Although the 3.5" mirror of the Questar cools down much more rapidly than a larger mirror, some people find the need for even an occasional refocusing to be annoying. Since a Zerodur mirror exhibits virtually no expansion or contraction as temperatures change, this option eliminates the need for refocusing, should this be a concern.

This Questar is protected by a ten-year Questar warranty (two-year warranty on the focuser mechanism).

Absolutely pinpoint resolution, total freedom from spurious color and distortion, with an image clarity and contrast in a class all its own - a Questar is truly the Rolls-Royce of telescopes. If you want the best small telescope in the world, Questar is it. Period.

Tech Details

Aperture 3.5"
Binary and Star Cluster Observation Good
Focal Length 1300mm
Focal Ratio f/14.6
Galaxy and Nebula Observation Fair
Heaviest Single Component 7 lbs.
Highest Useful Magnification 162x
Lunar Observation Great
Weight 7 lbs.
Planetary Observation Good
Resolution 1.3 arc seconds
Telescope Type Maksutov-Cassegrain
Visual Limiting Magnitude 12.2
Warranty 10 years


Review by:
I've owned Questars for decades now. A great scope -- razor-sharp images, impeccable engineering,, light and easy to use. The small aperture is a limitation, of course, but lunar and planetary observing it's a small gem. As a portable scope it's hard to beat. It's beautiful to look at and a joy to operate. (Posted on 7/22/2019)
Review by:
The Questar 3.5inch maksutov is a gem. Every part of it's construction is an example of the finest craftsmanship you can fine. Something simple like the smoothness of motion as the starchart dewshield as it moves over the OTA just exudes quality. Optically it is as good as it gets for a 3.5 inch scope. The fact that it is a maksutov makes it as portable as you can get. My father and I spent many nights doing planetary and lunar observation and photography. We would run power cables from the house out to a Concrete stabilized pier mount put in place for this purpose. Photography through the scope by prime focus was easy to set up- in those days with a 35mm film camera. The tracking system worked flawlessly assuming proper alignment - and the ability to flip the levers on the back of the scope to switch between eyepiece viewing and photographing, as well as the built in barlow made it so easy to focus on what is important about astronomy - viewing the night sky. Planetary and lunar viewing was outstanding and helped to ignite in myself a life long interest in astronomy. (Posted on 1/4/2019)
Review by:
Questar is to Astronomy what Leica is to Photography: An optical jewel in a outdated and timeless craddle.
If you like M3, manual gearbox, vinyl record, lever espresso machine, this is for you.
Can do planetary and DSO astrography with effort and pugnacity (Posted on 11/19/2018)
Review by:
So few things these days are made the very best they can be without regard to cost. Thankfully the Questar is still one of them. Everything about it is a joy to look at and use. The view is superb, as long as one remembers it is a 3.5-inch telescope and is not going to gather the same light as an 8-inch scope. Planetary views are wonderful. (Posted on 10/6/2018)
Review by:
In my opinion the Questar is the best portable telescope you can buy. While expensive, it is beautifully designed, manufactured to high precision and very easy to use. Optically it is as good a scope of its aperture as can be made. Easily airline portable, I have traveled thousands of miles with mine. With the built-in Barlow and the supplied eyepieces and solar filter you have a complete, compact observing package. (Posted on 8/4/2017)
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Supplied Accessories

  • 1.25" 16mm and 24mm eyepieces (54x to 120x, depending on eyepiece and whether built-in 1.5x Barlow is used)
  • Built-in 4x finder (6x when 16mm eyepiece is used)
  • Aluminized and overcoated pyrex mirror
  • Magnesium fluoride coated optics
  • Built-in star diagonal
  • Dual arm fork mount
  • Setting circles (r. a. circle power driven)
  • Sidereal rate AC motor drive (2.7 watts)
  • Manual slow motion controls
  • Thread-in dust cap
  • 1.5" aperture off-axis solar filter
  • Solar filter for finder
  • Tabletop tripod legs
  • Locking hard case
  • Self-storing dewcap with embossed star chart
  • Embossed Moon chart on scope barrel
  • Ten-year warranty (two years on drive and focuser).