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Early Production Questar 3-½ Telescopes: 1954 and 1955An overview of the first production Questar 3-½ telescopes.
Here we will look at some of the earliest Questar telescopes made, and discuss how as refinements were devised these first or 'early production' telescopes and their accessories differed from mid, later and current production models.
Right: a first production model Questar 3-½ of 1954 cased at left, and in Pole Aligned mode at right (119,017 bytes). As explained in our article How to Choose Your Questar 3-½:
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Over the first year and a half of production Questar production grew to average five or six units sold per month. Between 1956 and the middle of 1961 sales increased to average almost eighteen units per month. The number of new instruments delivered between commencing production in the first five years was doubled over the following two years. The increase of sales parallels the growing increase in space prompted by the early manned space flight missions, an increase in science education and awareness of Eclipse events, and the growing recognition that the Questar was a unique and valuable instrument.
Since its introduction Questar has been immortalized in film and in books by respected people including Johnny Carson a national television icon, and renaissance man Arthur C. Clarke who wrote "the finest small telescope ever built--the 3-1/2 inch Questar, a jewel of precision optics which has produced close-ups of the moon that could easily be mistaken for Mount Wilson photographs". Among three Standard Questar telescopes made for the US Army Redstone Arsenal in May 1959 was one that was used by Dr. Wernher Von Braun; this telescope remains in service with the Kennedy Space Center amateur astronomy club.
The Questar is considered such a high accomplishment that one special 1965 Questar Standard 3-1/2 now resides in the collection of the Smithsonian Museum of Technology in Washington, D.C.; it is a unique cut-away instrument that reveals the various innovations unique to the Questar. These basic principles of the telescope remain unchanged, even after nearly sixty years in production.
Basic Configuration: the production 3-½ astronomical telescopes of the 1950's and those of today incorporate optics that are some forms of the Maksutov-Cassegrain optical design. Drawings and prototypes were in development from 1946 until finally entering commercial production in 1954 as a variation of the Maksutov-Cassegrain design the 'Denny Triple-Passage Meniscus' arrangement. This was suggested late in 1949 by Braymer's attorney Joseph Denny to avoid patent conflicts with established Maksutov-Cassegrain designs of the time. The design was ray traced and optimized by Braymer's friend, optical designer Norbert Schell.
The optical tube assembly mated to a dual tine fork mount and base. These early telescopes consisted of some 238 components, many of them unique to the Questar, provided by 103 subcontractors and suppliers. As shown to the right in the image at the top of this page, the astronomical Questar 3-½ telescopes are provided with a lightweight but rigid tripod so the mount can be Pole aligned and the drive will track celestial objects as they appear to move across the sky. The mount also incorporates features to help one learn and navigate the night sky.
These telescopes incorporate a Primary Mirror made of Corning Pyrex®. The Primary and Secondary Mirrors were coated with reflective aluminum, then overcoated with Silicon Monoxide (AlSiO) a hard protective coating to prevent oxidation of the aluminum. The thick meniscus Corrector Lens of these telescopes is made of borosilicate crown glass. This lens and the internal optical elements in the Control Box are antireflection coated with Magnesium Fluoride (MgFl) to increase transmission by up to ninety eight percent per surface. By 1958 Questar customer would be offered the choice of the standard Pyrex® Primary Mirror or at extra cost the more thermally stable Quartz Primary Mirror substrate. By the 1970's optional Broad Band coatings that improved throughput of the entire system would be among the available options.
The Fork Mount and Base assembly supports the telescope rigidly, and allows the user to point the telescope up or down in altitude or in astronomical terms 'Declination' motion. The motion is smooth and is controlled by a manual friction drive control knob on the side of the fork. The fork mount Base also permits the assembly to be rotated left or right by means of the manual friction drive control knob on the top of the fork base.
As the Earth rotates these objects appear to move across the sky in an arcing direction referred to as Right Ascension. This Base houses an AC current powered synchronous motor and drive gear set. The motorized drive provides when the telescope mount is Pole Aligned parallel to the Earth's axis of rotation, the mount will drive the telescope to track celestial objects at a Sidereal rate; this is moving one full rotation in 23 hours 56 minutes and 4 seconds. The drive Base is furnished with a 120 Volt A.C. (or 220 volt optional) motor with a power cord that plugs into a socket at the bottom cover of the Base. The 2.7 watt motor is made by Cramer, ½ RPH with a sealed and lubricated gear train. Since the AC motors rotation is not reversible Questar provided a motor with the correct voltage and rotation to be used at the customers location either in the North or the Southern Hemisphere, the motor could be changed for those traveling to another hemisphere.
The tripod is an arrangement of two fixed length side legs that slide into the holes along the side of the Base casting, and one adjustable length center leg which threads onto the center of the Fork Mount Base. In order to align the axis of rotation of the mount with that of the Earth one tilts the fork mount atop a tripod so that the center leg parallels the Earth's axis of rotation and the imaginary line running through the center of the leg and up through the fork mount points to the Celestial Pole. To Pole align the mount the mount is moved left or right to point the fork towards the Pole, while the length of the Center leg is adjustable from between 10-5/8 to 18-11/16 inches to permit the user to adjust the tilt of the Fork Mount and Base. Each leg has a protective non-marring and non-slip black rubber tip so that it will not mar a tabletop. For the Questar astronomical telescopes made through the late 1960's both fixed length legs slip into the Base casting, while the center leg slides into a socket in the base. The two tripod leg ports on the side of the Base casting are provided with gasketed removable plugs.
When properly Pole aligned and tracking then the mount's tracking motion counters the apparent motion as Earth rotates about its axis so that these objects appear motionless and suspended in space at the eyepiece. The Questar can keep the objects in the field of view of an eyepiece or camera thereby removing the distraction and difficulty of manually trying to follow objects precisely across the sky. The tracking feature also facilitates sharing the telescope with young or inexperienced observers. The manual and mechanical mechanisms are friction drives so there is no periodic error (as there will be with worm gear drives) and this facilitates employing the telescope for astrophotography.
With the provided functional Moon Map and Star Chart on the telescope barrel and Dew Shield, and by using the Declination and Right Ascension setting circles the user of the Questar can learn much about celestial navigation, and how to find the otherwise unobservable objects that might otherwise go unnoticed. These early charts incorporated features to make the more readable in low light including embossing and texturing so that the major features into the metal covering. The aluminum stock was provided by Alcoa, not always meeting the standards required by the Metal Etching Corporation who made the star charts and moon maps. This manufacturing technique would be discontinued by the late 1960's when the charts became silk screened. The original style embossed charts would be brought back as a feature of the deluxe 50th Anniversary Model telescopes released in September 2000.
The Declination Setting Circle is made of machined steel stock, with the degree numbers and hash mark increments engraved and painted black. The Declination Setting Circle is provided on the left side of the fork mount, the circle on the right side is a component of the elevation friction drive.
The distinctive flared cylindrical Base is cast from corrosion resistant aircraft grade virgin aluminum 356-T6 heat treated alloy then is hand turned, then machined. As 356 alloy will not color anodize this is hand polished to a pewter sheen, over time the natural metal finish can be renewed simply by polishing. As described by Lawrence Braymer:
The 5/8 inch (15.75 mm) diameter tripod legs are made of lightweight Aluminum 61 S-T3, each is centerless-ground to 0.0001" then anodized. The tripod hole plugs in the Base of Questar telescopes made from 1954 to the late 1960's served two functions, one as hole plugs and the other as attachment screws for hanging the telescope onto a suitable panel such as a half open car window. This is a most precarious looking arrangement, but one that worked for some people for terrestrial observing. The rotating capability of the barrel allows the eyepiece to be rotated to away from the car to facilitate access. This is pictured on page 7 of the 1960 edition Questar booklet available for download at our Questar Notes & Interesting Articles on line archives.
Right: left rear view of 1955 Questar 3-½ in Company Seven's Museum Collection (103,682 bytes).
The controls and components are:
The Finder in the telescope consists of an ⅛ inch thick elliptical pick off mirror attached onto a 45 degree inclined support brace, this assembly is attached to the bottom of the Control Box. Light comes from the distance into the mirror then is deflected up and through the Finder Objective Lens located at the bottom of the Control Box. The light is focused by this lens into the area of the eyepiece Field Stop. The early Questar telescope eyepieces are a two piece threaded assembly so that the lower section threads onto the eyepiece holder, while the eyepiece upper section (housing the optics) can be rotated up or down to reach focus at the finder setting.
2. An Amici image erecting prism is built into the Control Box of these early Questar telescope. When the Finder/Telescope selection dial is rotated counterclockwise so that the lever points up, then the prism slides into place at the center inside the Control Box so that when light comes out of the telescope's main optical tube into the Control Box the prism diverts the image so that it will appear at the eyepiece. The Amici prism corrects the image orientation so that it will appear right side up and correct left to right.
The Amici image erecting prism was built into Questar telescopes made between May 1954 to May 1959. To provide improved resolution this was changed in June 1959 so that every Control Box is provided with a Star Diagonal prism so the image at the eyepiece appears right side up, but reversed left to right.
3. A magnifying (Barlow) lens that can be dialed in or out by the topmost knob on the Control Box. Rotate the control dial counterclockwise to move the Barlow lens off line, or clockwise to engage the Barlow when observing through the main telescope. Note, the Barlow is incompatible with the Finder operation - eyepieces will not focus if the Barlow is in line while attempting to look through the Finder.
4. The focus control of the telescope is by means of an internal arrangement where the Primary Mirror moves forward and back within the telescope thus there is no change of physical length when focusing. Focus us controlled by the knob below and to the right of the Axial Port. Turning the focus dial clockwise moves toward infinity and beyond, while dialing counterclockwise moves to focus onto objects closer and closer to the telescope. On these early telescopes the knob has two diameters thereby facilitating a form of coarse or finer focus control, this changed in 1959 to the button style that remains in production to this day.
5. Thread on eyepiece adapter tube at the top of the Control Box. The two eyepieces provided from the 1950's into the late 1960's differ from modern Questar Brandon eyepieces in their attachment mechanics and thus are not interchangeable. The eyepiece adapter tube can be unthreaded from the top port of the Control Box and then attached onto the Axial Port for in-line work.
6. Axial Port at center of the Control Box, this accepts optional hardware including Camera Adapter. With the telescope set to Finder mode the light will pass from the main telescope tube to the Axial Port, and with the cap removed the light will continue out to an optional camera or other device. On Questars made from 1954 to the late 1960's this port is 0.95 inch diameter, later production telescopes will have 1.2 inch diameter ports for better performance when imaging and with some other optional accessories. We do offer adapters to permit the use of newer accessories onto the early Questar telescopes, although there may be vignetting of some modern accessories.
The Control Box casting of the Questars is made of an aluminum-silicon alloy, this inherently provides good corrosion resistance. And the expansion coefficients even at subzero temperatures are some ten to twenty percent lower than those of pure aluminum. The focus knob, dials and Axial Port cover are machined from aluminum 24S-T4 heat treated corrosion resistant alloy, the dials feature stainless steel levers. These parts too are hand-turned on turret lathe.
Above: early production Questar telescope completed in 1955.
Early Production Models: incorporate a Maksutov-Cassegrain optical design that provides a nominal effective focal length of 1,070 mm at f/12. This difference between the optics of the early models and those of 'mid production' telescopes and late production models with longer focal lengths that followed is difficult to tell simply by looking at or through the telescope.
However, those telescopes made between 1954 and into early 1956 can be most readily differentiated from the later production telescopes because of the red, silver and blue "Questar" declination axis cover plates. These are affixed to either side of the Fork Mount arms with contact cement. The plates read "42" APOCHROMAT F:12", Questar, NEW HOPE PA•U•S•A•" (yes there was a time when tangible items were made in the USA). These early discs are glued onto the ridge of the circle on the Fork Tine thus it is more likely to snag or be knocked off than the later example where the disc is glued in but recessed below the ridge level of the casting, so the mid and later production telescopes are less likely not to have lost their Fork bearing cover disc.
Looking for these covers on an older Questar is not always a reliable way to judge the age of the telescope since during the course of routine use and transport or during servicing visits these original disc could be snapped off and they may have been replaced by later versions. Close inspection of the cover in the image above right shows signs that someone pried this cover thereby marring the edge, this likely happened during servicing. Over the recent years we have become more careful to preserve the historic integrity of older Questars by employing time consuming methods to remove the covers but without damaging them so that the originals can be attached into place after the servicing.
The telescopes made in 1954 can be distinguished from late 1954 and 1955 production by the Finder pick off mirror bracket. The 1954 production employ an angled steel support to suspend the Finder mirror at the lower six O'clock portion of the Control Box, this bracket is tilted at forty five degrees so that the image is directed from the mirror up to the Finder objective lens. This arrangement can be seen in the illustration at top right of this page. It soon became apparent to Questar that the Achilles Heel of this otherwise durable instrument was the support bracket of the Finder pick off mirror. This original arrangement exposed the pick off mirror to dirt and the protruding bracket was prone to snagging or bending by impact that would produce a misalignment of the mirror thus rendering the Finder inaccurate if not completely useless. Later in 1954 this arrangement was changed so that the pick off mirror is provided improved support and protection. In this arrangement the mirror is glued onto a pivoting plate. The mirror and tilt plate are attached onto the Base of a 'U' shaped steel housing by four screws, the screws adjust the tip and tilt of the mirror so that the image shown in the Finder is centered in the view through the main telescope. The entire assembly is attached to the bottom of the Control Box by four short bolts. In time Questar modified the production lacquering the steel pick off mirror housing to prevent oxidation.
The change of design of the Finder pick off mirror housing would spur the development of yet another innovation in the late 1960's: the installation of a Solar Filter for the Finder. This Solar Filter mechanism is hinged so that the user could swing the filter element over or away from the Finder lens (between the mirror and the lens). By having this in place one completely eliminated the risk of accidentally switching from viewing through the main telescope with its Solar Filter attached to the Finder mode that up the then had no solar filter protection. To this day no other manufacturer has been so thoughtful to provide such a convenience built-in to their telescope!
Other distinctive aspects shared by the early production telescopes are the scalloped hand knobs attached onto either side of the Fork Mount. On these the attachment bolt at center is visible. These knobs control the elevation lock and elevation motion fine control. The knobs of Questar telescopes made since late December 1955 are similarly machined from solid aluminum 24S-T4 stock however the center is solid and not machined out as on these early telescopes, and these are attached by a bolt threaded from the inner side of the fork so no attachment hardware is visible.
The Control Box casting of the Questars made from 1954 into early 1956 has a natural, polished metal finish. Production models from early 1956 to the present day will have the Control Box but the exterior is hand sanded, primed, then painted silver.
For models made from 1954 into 1956 information including the telescope Serial Number, Questar patents information, the voltage and cycles of the motor installed in the Base were hand engraved onto the cover at the bottom of the Base. This engraving is usually located between the center opening for the tripod leg and the AC wall plug socket. On these early telescopes one will read something like this:
The use of a Synthane backplate complicates alignment and other servicing these early telescopes since it is not practical to remove the optical tube barrel from the Synthane backplate. As mentioned above, these telescopes incorporate an image erecting Amici prism in their Control Box.
In time Questar discovered the threads tapped into the Synthane backplate wear out from the friction of the honed stainless steel threaded shaft. The wear progresses so that 'mirror shift' while focusing becomes more and more pronounced, the smoothness of focusing degrades, and eventually the threads wear out altogether so the user can not focus until the back plate is replaced. So Questar gradually moved away from using Synthane and instead relied on machined aluminum for these components.
The accessories provided as standard with these early telescopes for $795 included:
1. 40X Eyepiece
Into 1956 the early Questars were shipped in a protective Leather Carrying Case (described below) but with no Lens Cover since it was assumed the case could provide satisfactory protection of the Corrector lens. The only provided accessory for the front of the telescope was the Solar Filter (shown above at center) that snapped into place held by three gasketed tabs pressing against the Synthane front cell's inner radius. Questar changed the design of the optical tube front cell so that the 95 mm diameter radius was threaded to accept a new lens cover or the provided revised Solar Filter. Questar simultaneously devised a thread on Lens Cover to protect the Corrector Lens of the telescope. The lens cover was made with the black disc made of the lightweight Synthane material with a lightweight aluminum alloy edge trim glued onto the Synthane. The center is covered with a Questar logo disc glued into place.
The fork tines of early to mid production Questar telescopes feature gloss reflective polished edges with the recessed areas on the face of the fork tines painted silver. By the mid 1980's the quality of the castings being provided caused the company to change from polished edges to a fine vertical milling that leaves a satin appearance.
As mentioned above, the early production Questars like this one also have an etched and filled Moon Map, Star Chart, and Right Ascension Setting Circle instead of the silk screened versions produced for later production units.
Eyepieces and Magnifications: the early and mid production telescopes were engineered to accept either of two provided Questar eyepieces. Each eyepiece consists of a knurled barrel that threads onto the telescope eyepiece holder, and the upper assembly housing the optical elements and Field Stop. To focus the eyepiece onto the Finder of the Questar simply rotate the eyepiece upper assembly clockwise or counterclockwise thus bringing the eyepiece Field Stop closer to or farther from the Finder's objective lens. The provided eyepieces are:
1. Questar 40X: 26mm König lens design with a 50 degree apparent field of view (18.03 mm Dia. Field Stop), and
2. Questar 80X: 12mm Erfle a five element wide angle lens claiming a 75 degree apparent field of view (16.55 mm Dia. Field Stop).
The Barlow lens built into the Control Box of these telescope was represented as providing an amplification factor of about 2X. Our acceptance testing at Company Seven over some decades during the course of delivering new Questars, and while servicing Questars indicates the magnifications provided from production lot to lot may vary.
The original optical design for the early Questar telescopes did not envision them operating them at magnifications much higher than 200x. The optical design of these telescopes has the Secondary Mirror deposited onto the front surface of the Corrector Lens so that this original arrangement combined with some other factors produced a system that is not as able to provide images as clear at higher magnifications or as bright as modern Questars. And yet under a critical star test a well adjusted early Questar can show a nice diffraction pattern since the optics shop making the optics then (as now) hand matched each set of optics to assure proper figuring. Late in the 1960's the design of the optics would be modified, overall specifications made more stringent, and improved materials and coatings offered. These changes along with new choices of Brandon eyepieces would provide the later production telescopes with truly amazing high magnification performance.
The case is designed to hold the Questar telescope with all its standard accessories. The accessories provided with the telescope are stored in leather pouches sewn onto the interior of the door lid. This arrangement is illustrated by the image at the bottom right of this article.
Right: Original Questar Leather Case in Company Seven's Museum Collection (74,161 bytes).
The case is laid out well and is compact, light weight (especially compared to modern Questar cases), and is beautiful. There are some aspects that are unusual:
The door lid is secured by two nickle plated steel spring loaded keyed laches, these are made by Cheney in England. But do keep in mind these locks only serve to keep the honest person honest.
First Class mail rates remained at 3 cents for a one ounce letter from July 1932 until August 1958. So the cost of postage for sending this Questar to its original owner in 1955 amounted to $1.77, as can be seen on the image of the original address label this was made up with three 50 cent stamps, one 20 cent stamp and one 7 cent stamp. This included basic postage for delivery, insurance for the full value of the telescope, return receipt including the 3 cent stamp for the return receipt card.
A common measure of inflation in the U.S. is the Consumer Price Index (CPI), which has a long-term average of 3.1 percent annually, from 1925 through 2008. Adjusted for inflation the postage charged $1.77 in 1955 should be about $14.26. But of course gasoline then only cost 29 cents per gallon so it is not entirely fair to expect the modern Post Office to deliver a new Questar based these figures.
What is most amusing about these labels is how they, as does the Questar telescopes described here, reflect America at an entirely different time when life was affordable on a one income earner's salary.
Right: carrying case interior arrangement with standard accessories: Solar Filter, Aperture Stop, 40X Eyepiece (the shorter of the two) is installed, the 80X Eyepiece is stored in case lid pouch, AC Power Cord (wrapped as provided), Tabletop Tripod Leg set. The keys and a spline wrench are in the pouch (84,199 bytes). Telescope is shown at Company Seven's Museum Collection.
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These early production Questar telescopes incorporate some components made of Synthane, a dimensionally stable and lightweight Bakelite tube made by the Synthane Corporation. Synthane sheets consist of a laminate of fibrous sheet materials such as cellulose or asbestos paper, or a cotton or asbestos or glass fabric, saturated with a thermo setting resin. This is cured over time under high temperature and pressure. These components included the Corrector Lens front cell, the optical tube assembly backplate (the wall between the Control Box and Primary Mirror), and the cover at the bottom of the Base.
Postage: we at Company Seven are frequently amused to meet people who have kept virtually every shred of paperwork that ever was involved with their early production Questar telescope. Maybe the kind of person who was more likely to by a Questar in the 1950's was more meticulous? After all $795 in 1954 adjusted merely for inflation alone would be in 2010 some $6,400. So it came as not too great a surprise to find the original shipping labels with postage affixed included with some of these old telescopes that we have acquired.
