Questar 3.5″ Telescope Duplex, Broadband coatings, Zerodur Mirror, Factory Installed Powerguide III

Description

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.

A Questar Powerguide III DC drive system/drive corrector is factory-installed into this Questar Duplex. It replaces the AC motor and 110V power requirement of the standard Duplex. The Powerguide III has a DC servo quartz drive that powers the scope’s drive motor for up to 50 hours from a single 9 volt transistor radio battery. This frees you forever from the need to stay near an AC outlet to observe the skies. The Powerguide III smoothly tracks the Moon, planets, star clusters, galaxies, and a host of other deep space objects across the heavens for you, keeping them centered in the eyepiece all night long. 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.

Pushbuttons on the quartz-controlled Powerguide III hand control allow single axis guided astrophotography with 1.4x and 10x sidereal guiding rates in right ascension (dual axis with 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 Duplex anywhere in the world without having to worry about finding the proper power frequency or voltage, or having the right kind of AC adapter. With the factory-installed Powerguide III, the Questar Duplex is truly a use-anywhere/use-anytime telescope!

This broadband-coated Questar Duplex includes ultra-high transmission/low reflectivity 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 compares with a light loss of 1% per surface with standard magnesium fluoride antireflection coatings. 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, for an additional improvement in light transmission of 10% per surface. The broadband coatings package gives you a full 22% overall gain in light transmission and contrast that’s very useful for photography and low light terrestrial observing and for viewing faint deep space objects at night.

This broadband coatings package is not recommended if you live full time on ocean-front property, or spend much of the year 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 scope’s future, consider the Questar Duplex with standard optical coatings (Questar model #QD3PG), 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.

The scope’s thermally-stable Zerodur ceramic mirror eliminates the minor need to refocus the scope as it cools to ambient temperature in situations involving large temperature swings. With a conventional Pyrex mirror telescope, if the difference in temperature between indoors and outdoors is 30 degrees or more Fahrenheit when the scope 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, the Zerodur mirror in this scope eliminates even the need for minor refocusing when the optical tube is taken outside in cold temperatures for a quick terrestrial photography session, or the complete scope is taken out during a winter’s night for some star-gazing, should this be a concern or an inconvenience.

This Questar is protected by a ten-year Questar warranty (two-year warranty on the focuser mechanism, five years on the broadband coatings).

Absolutely pinpoint resolution, total freedom from spurious color and distortion, total freedom from temperature-related focusing issues, with an image clarity and contrast in a class all its own, the multifunction ability to convert in seconds from an astronomical telescope to a terrestrial spotting scope and telephoto lens, AC cord-free battery-operated operation – this Questar Duplex with broadband coatings and a Zerodur mirror is not only the “Rolls-Royce” of telescopes, it is the “Swiss Army Knife” of telescopes. If you want the best and most flexible small telescope in the world, this Questar Duplex is it. Period.

Tech Details:

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)
• VHR silver coated and overcoated Zerodur glass ceramic mirror
• Broadband dielectric multicoated optics
• Built-in star diagonal
• Dual arm fork mount
• Quick disconnect optical tube with built-in photo tripod adapter for terrestrial use
• 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).