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Unitron Model 142 - 3" (75mm) Achromatic Equatorial Telescope

“among the first ’telescope-looking telescopes’ that many of us first aspired to own”

    A discontinued product, posted for information purposes by Company Seven and with a historical perspective about the company who made it.
    The Unitron illustrations here are from literature and show the Model 142 in Company Seven’s museum exhibit of telescopes.

Contents and Quick Links: click on the to return to top of this article
Red ball (924 bytes) Preface

Red ball (924 bytes) Background: Who Were Unitron, Polarex, Nihon Seiko?

Red ball (924 bytes) The Unitron 3 Inch Equatorial Telescope

Red ball (924 bytes) History: Start Of The Space Age

Red ball (924 bytes) Specifications Of This Telescope

Red ball (924 bytes) Pertinent Documents and Literature In Our Archives

Unitron 3 inch telescope, Model 142 displayed at Company Seven (87,379 bytes) Preface: in February 2011 Company Seven acquired the Unitron achromatic refracting telescope that is featured in this article for our collection. It was picked up by one of our technicians who on 1 May flew to Michigan to pack it securely there and then drive it safely to Company Seven. This is among several used or consigned Unitron telescopes that have crossed our threshold over recent decades, but this is only the second Unitron telescope to be selected for permanent retirement to our display joining our Unitron Model 114 a 2.4 inch (60mm) telescope.

Right: Unitron Model 142 - 3 inch (75mm x 1200mm) telescope with Sun Projection Screen attached. Note the optional: Unitron finderscopes, UNIHEX, DEUTRON, 2.4 inch (60mm x 70mm) photo guide telescope, electronic Clock Drive, and Gieseler Electronics AccuTrak Drive Corrector (76,120 bytes).
Click on image to see enlarged view (245,261 bytes).

In terms of mechanical quality, consistency, and comparative comprehensiveness of the system UNITRON was among the better telescope brands sold in the USA. These telescopes, mounts, and accessories were manufactured in Japan and distributed in the Americas from 1951 to about 1992. Their refracting telescopes were geared for the amateur astronomer and school science class markets. As Unitron prospered their offerings grew from the initial smaller models including the 2.4 telescope, up to massive 9 inch (225mm or 8.8 inch) telescopes made for permanent observatory installations. Unitron also came to offer microscopes and other scientific instruments, some that shared accessories or parts of accessories made for use with the astronomical telescopes. These instruments provide good performance in their day, beautiful appearance - they looked good just standing there, and were versatile given their well integrated system of accessories. While our community was saddened by the demise of the telescopes production, the Unitron company continues to distribute microscopes and other equipment. There are other companies bearing the Unitron name, including one distributing hearing aids, but these are not the Unitron that sold telescopes.

The owner of Company Seven has been on a mission for decades to quietly promote science education through astronomy. We do this by helping to develop and sustain regional astronomy clubs, by donating equipment and expertise to start new astronomy programs overseas for elementary and junior high school age children locally with our own observatory and showroom, where we conserve and display telescopes and other instruments that have been worthy of note for attracting youth to astronomy, particularly those that have had notable impact since the dawn of the Space Age.

Company Seven had been keen to acquire a Unitron 2.4 inch alt-az and also a Unitron 3 inch equatorial telescope for our exhibit since these are among the few landmark production telescopes that gave thousands of people their introduction to astronomy. While our Unitron Model 114 telescope represents the pinnacle of the smaller refracting telescopes, among the best that a beginning amateur throughout the 1950’s and into the 1960’s might have aspired to own, this Model 142 represents the most practical of the Unitron portable equatorial telescopes. In terms of prioritizing choices we were more interested in finding a 3 inch photo equatorial model more so than the 4 inch or larger models since the larger telescopes are so heavy and cumbersome that they tended not be used as often. The larger telescope likely did not fit (set up) in a typical room owing to their exceeding the height of most home ceilings. At Company Seven our ceilings can accommodate much larger telescopes, so we display or store several Carl Zeiss refractors and show modern state of the art Astro-Physics apochromatic refractors up to 206mm (8.15 inch) for example. In August 2014 we acquired a late production Unitron Model 132 4 inch (102mm) Equatorial Refractor, and later we added the more common Unitron Model 152 4 inch (102mm) Achromatic telescope to our exhibit; these 4inch telescopes are exhibited alongside our Model 142/145 for comparison and nearby our Model 114. We deem each of these to be significant enough to preserve and display.

Configurations Nihon Seiko, the manufacturer of Unitron, sold most of their transportable telescopes in either of two basic configurations: with an alt-azimuth mount suitable for terrestrial and visual astronomy use, or with a German Equatorial Mount that is better suited for astronomy uses. The 3 inch telescope was available as a package including eyepieces and with finderscope on their alt-azimuth mount with wood tripod as the Model 140, basically a larger version of the Model 114 a 2.4 inch telescope that we already show at Company Seven.

Unitron Model 142 - 3 inch Equatorial telescope from 1972 Catalog (54,097 bytes) The Model 142 differs from the Model 114 already in our display in two obvious notable respects, these justify including it in our display collection:

    1. the Model 142 telescope is provided with a German Equatorial Mount.

    2. the Model 142 system main optical tube assembly is built upon a larger diameter 75mm objective lens, with a longer 1,200mm focal length. The 75mm f/1,200mm objective (front) lens, about 114 times the light gathering power of the unaided human eye; this is about 1.56x greater than that of the next smaller Unitron 2.4 inch telescopes.

Unitron offered a visual system based upon the 3 inch telescope with their German Equatorial Mount, this was marketed as the Model 142 3 inch Equatorial Refractor. The set was provided with five eyepieces, Achromatic Amplifier (Barlow Lens), 8x 30mm Finder, and Sun Projection Screen.

Right: Unitron Model 142 - 3 inch Equatorial Refractor, as illustrated in the 1972 catalog (54,097 bytes).
Click on image to see enlarged view (280,156 bytes).

The 3 inch Photo-Equatorial telescope in our collection is among the later production examples. The telescope was ordered new in 1975 by the late Mr. Norbert E. Krieg of Saginaw, Michigan. Then the customers had a choice of standard accessories including either the 90 degree inclined Star Diagonal (for astronomy uses) or the UNIHEX accessory; this telescope was ordered with the Star Diagonal. Mr. Krieg added numerous optional accessories by Unitron including their ASTRO-CAMERA 220, and several other Unitron items described below, and some third party options too.

The German Equatorial Mount provides:

  • Manual geared controls to facilitate tracking objects as, owing to the rotation of the Earth, they appear to move across the night sky, this makes it less distracting than an Alt-Az mount to study an object. Furthermore, it is much easier to share the telescope with others over an observing session particularly if they are inexperienced in operating manual controls. These controls can be motorized to allow automated tracking of the celestial objects with precision good enough to allow photography of the objects and other projects that require precisely keeping the telescope optical tube pointed onto the target over time.

  • The capability to vary the payload on the mount over a greater span than the alt-azimuth mount by simply adjusting the quantity of and position of counter weight on the shaft that extends from the mount on the side opposite the payload.

  • Facilitates finding celestial objects overhead with the telescope by means of the provided setting circles. These are an aid to navigation whose moving numbered dials correspond to the two dimensional grid systems used to navigate the night sky.

The Model 142 and Model 145:

Unitron Model 142 - 3 inch Equatorial telescope from 1972 Catalog (50,907 and 261,476 bytes) Unitron also offered the 3 inch telescope with the German Mount, the Model 145 set was marketed as the 3 inch Photo-Equatorial Refractor. This configuration was provided with six eyepieces, choice of either the Star Diagonal or the UNIHEX, and with other components to facilitate film astrophotography. The set also includes an auxiliary 2.4 inch x 700mm focal length photo guide telescope, and an auxiliary 10x 42mm Finder; both smaller telescopes are attached in parallel alongside the 3 inch telescope. To help balance payloads at the rear of the main telescope a counterweight system is also provided, attached and parallel to the main telescope.

Left: Unitron Model 145 - 3 inch Photo-Equatorial Refractor with several options, as illustrated in the 1972 catalog. Note the standard De-Luxe model focuser (54,097 bytes).
Click on image to see enlarged view (280,156 bytes).

This Unitron Model 142 telescope in our display is unusually complete and intact consisting of the 3 inch (75mm) aperture f/16 achromatic refractor optical tube assembly (or OTA). The Unitron telescope optical tube assemblies are constructed from rolled and welded aluminum tubes, in the case of the 3 inch models these incorporate a tube of 3-116 inch diameter. The telescope optical tube accepts the lens cell at the front, and either a Unitron Standard Focuser or their De-Luxe rack and pinion Focuser at the rear. Either focuser can accommodate the then common visual accessories of 0.965 inch or 1.25 inch diameter.

The earlier production Model 142 and Model 145 optical tubes were provided with the same basic focuser, but either telescope could be ordered with the optional De-Luxe Focuser. The De-Luxe version differs from the standard focuser by incorporating manually operated locking clamps so that the user can secure the drawtube at any extended distance; this feature can prevent the weight of an attached payload from inadvertently shifting focus while observing or taking astrophotos. The De-Luxe was an upgrade focuser offered for the Model 142 and Model 145 telescopes made since the 1950’s, later (certainly by 1972) this focuser was provided as standard equipment on the Model 145, or the focuser could be purchased separately for other Unitron telescopes or by telescope-making amateurs for their own project.

The Model 142 telescope acquired by Company Seven arrived with the De-Luxe Focuser installed, although initially we could not explain how it came to be on this telescope. Later in 2012 the family of the original owner found the Unitron Standard Focuser stored away, that had been sold with this Model 142 in 1975 so we concluded the former owner bought then retrofit the current De-Luxe Focuser onto this telescope as he progressed into astro-photography.

As the Unitron telescopes entered the market in the 1950’s, a drive system to automate tracking along the Right Ascension (R.A.) axis of the German Equatorial Mount was not provided as standard equipment but was optional. This was also the case with either the Model 142 or Model 145 sets, although this could be ordered later with either telescope marketed as the Model 142C or Model 145C; the C suffix should not be confused with that of the late production folded refractor telescopes (Models 131C, 132C, etc.). This is an AC powered synchronous drive, that could be powered either from AC current (choice of 115 or 220 volt AC) or through an optional third party Drive Corrector that permitted operation of the motor from either AC or 12 volt DC sources. Most telescope Drive Correctors of the period permitted the user to make fine adjustments to the tracking speed by dialing to a Sidereal, or Solar and or Lunar rate. The more sophisticated Drive Correctors included a hand held controller that made it easy for the user to make momentary corrections of Right Ascension (and Declination if the telescope mount had the second drive) that might be necessitated by the worm gear error or by slight Pole Alignment errors.

The Unitron 75mm telescope set we display includes the 142/145 series Equatorial Mount with Wood Tripod. The Model 142 set originally included a 8x 30mm finder telescope, choice of either a UNIHEX or 90 degree Star Diagonal, Sun Projection Screen (6 x 6 inch), Sunglass, Pocket Eyepiece Case, Dewcap, Dustcap, an assortment of eyepieces with prism diagonal or UNIHEX eyepiece holder, wooden cabinets, instructions sheets. Also included was a set of five (5) eyepieces to provide a range of useful magnifications with the telescope. All of the components fit neatly into either wood case. The Model 142 telescope in our collection also includes the Unitron AC Clock Drive and with a Gieseler Electronics AccuTrack Model 2117B Single Axis Drive Corrector, that provides square wave AC power to the Right Ascension motor. Gieseler Electronics, founded by Time Gieseler went on to sell third party telescopes too and in time branched out into the selling of imported telescopes bearing the Orion Telescopes brand.

The telescope we show here was sold new in May 1975 as a Model 142. However, presently this set includes
all the accessory features of the Model 145 including the upgraded focuser, and with many more options too.

Unitron 3 inch Photo Equatorial telescope right side view (53,541 bytes) Unitron 3 inch Photo Equatorial telescope right rear view (57,581 bytes)

Unitron 3 inch Photo Equatorial telescope right side view (47,119 bytes) Unitron 3 inch Photo Equatorial telescope right rear view (54,454 bytes)

Above: Unitron Model 142 3 inch Equatorial Telescope with optional 2.4 inch photo guide telescope,
AC powered clock drive, auxiliary finderscopes, UNIHEX, DEUTRON (each image Appx. 50 kbytes).
Click on each image to see enlarged view (each image Apprx. 240 kbytes).

This system is so lightweight that an adult can pick up carry the assembled telescope and mount, however it is too cumbersome to carry for any distance or through an average doorway. Alternatively one could employ a wheeled dolly to facilitate rolling the set in and out of a garage or porch for example.

The system consists of the basic telescope with numerous options, most listed below, including the UNIHEX accessory that permits the user to store as many as six (6) eyepieces at the rear of the telescope dialing in one eyepiece after another thus varying the magnification at will. The telescope set also includes an optional DEUTRON, an accessory that allows one or two observers to simultaneously observe the same object through the telescope. For astrophotography there is an optional ASTRO-CAMERA 220 too. The UNIXEX, DEUTRON, and ASTRO-CAMERA 220 are each provided with their own separate fitted wood boxes.

* Prices listed did not include shipping, or Sales Tax if applicable.

** Prices listed when first known, introduced after 1956.

Prices* Over The Years Of The Unitron 3" Equatorial Telescope And Our Accessories
Item Price In 1956 Price in 1974 Price in 1985
Model 142, 3" Equatorial Telescope cased set $435.00 614.00 1,298.00
Model 145, 3" Photo-Equatorial Telescope cased set
listed for comparison only
$550.00 905.00 N/A
De-Luxe Rack & Pinion upgrade $15.50 15.50 10.00
UNIHEX A $24.75 35.25 80.00
DEUTRON A $23.50 41.00 84.00
Second 8x 30 Finder (Incl. Mounting Rings) $10.75 21.50 65.00
10x 40 Finder (Incl. Mounting Rings) $18.00 33.75 90.00
Synchronous Motor Drive 115v, with hardware $60.00 115.00 167.00
2.4" photo guide Telescope (Incl. Mounting Rings) $81.00 123.00 230.00
Extra Counterweight to Balance photo guide Telescope $4.75 9.80 15.00
ASTRO-CAMERA 220 $69.50 155.00 N/A
UNIBALANCE Tube Weight System $15.50 26.00 57.00
3" UNICLAMP Piggyback Camera Bracket $3.75 14.75 31.00
Sun Diagonal (Hershel Wedge), 0.965 inch Model A $17.50** 29.00 63.00
Sun Diagonal (Hershel Wedge), 1.25 inch Model B $22.50** 37.25 95.00
40mm MONOCHRO, 1.25 inch eyepiece $14.75 21.00 38.00
Telescope objective lens cleaned and installed into cell (36,869 bytes)

Above: this Price List of Sep 1974 is among the documents provided with our Model 142 telescope.
Click to download the 3 page .pdf file (4,067,035 bytes)

The optics of this telescope and of all the mechanical components are original, intact, and functioning well. Cosmetically, in terms of overall appearance we would rate this set a B on the scale of A to F; the set has only modest signs of normal and careful use.

Close inspection of the objective lenses of both the main 3 inch telescope and of the 2.4 inch photo guide telescope revealed fungus was growing in the narrow air gap space between the crown and flint elements. This required careful disassembly, professional cleaning, and reassembly. Throughout the process there must be a disciplined and proper technique; we will not explain how to do this work here because we do not recommend tampering with or disassembly of these lenses by those who are not trained in the work. Fortunately, we arrested the progress of the fungus and were able to restore both objective lenses to an as-new appearance. In fact our alignment process resulted in even better performance than when the telescopes were first evaluated at Company Seven, with the clear and concentric Newton’s Rings interference pattern delighting all who were allowed to observe them.

Fungus in telescope objective lens, as it was acquired (47,329 bytes) Telescope objective lens, removed from cell (41,820 bytes) Telescope objective lens cleaned and installed into cell (36,869 bytes)

Above left: Fungus in between telescope objective lens elements, as acquired (47,329 bytes).
Center: Telescope objective lens, removed from cell (41,820 bytes).
Right: Telescope objective lens cleaned and installed into cell (36,869 bytes).

There is some flaking of the black paint on the tripod leg tips, but this seems to be the norm as the tips of many Unitron tripods were not well primed before painting. Unfortunately there are no easily accessible serial production numbers on these telescopes, but our telescope is well documented and so we know when it was sold even if we can not say for sure when it was made. Even if some of the accessories dates to about 1972, an accessory could have been interchanged among other telescopes, or replaced years after the telescope was sold. The solid wood telescope and mount cases arrived in good condition, with no damage of note to the support braces inside as is often seen in other examples. The cases needed only some cleaning and conditioning before being added to the display. Since our general policy is to conserve antiques - to clean and protect them from decay, we display this telescope among our collection at our showroom cleaned and assembled but otherwise as it arrived.

Unitron 3 inch Photo Equatorial telescope optical tube case closed (76,172 bytes) Unitron 3 inch Photo Equatorial telescope optical tube case open (90,386 bytes)

Above: Unitron 3 inch Photo Equatorial telescope optical tube assembly wood case (76,172 and 90,386 bytes).

Unitron 3 inch Photo Equatorial telescope mount head case closed (31,819 bytes) Unitron 3 inch Photo Equatorial telescope mount head case open (50,430 bytes)

Above: Unitron 3 inch Photo Equatorial telescope mount head wood case (31,819 and 71,604 bytes).
Click on each image to see enlarged view (85,720 and 164,270 bytes).

Seiko Unitron and Polarex logos (113,246 bytes)

Unitron 2.4 inch telescope, Model 114 displayed outside Company Seven (309,461 bytes) Background: the telescopes marketed in the Americas under the trademark UNITRON were produced by Nihon Seiko Kenkyusho, Ltd. of Nozawa, Setagaya-ku, Tokyo, Japan. This company and its affiliates manufactured telescope and other scientific instruments. We have no substantial information about how Nihon Seiko Kenkyusho came to be, or when they developed their line of fine achromatic refracting telescopes. However, the company was established at least as far back as the the mid 1930’s, then furnishing fine achromatic telescopes of at least up to 125mm aperture to universities under the POLAREX and SEIKO SCOPE trademarks. By 1951 the company had emerged from the ashes of the war and offered an their first assortment of what was to become an extraordinarily well integrated and accessorized line of telescopes, mounts, and accessories.

Right: one of the first models offered by Unitron; a 2.4 inch Model 114 telescope of the Company Seven Museum Collection.
This instrument has the UNIHEX A accessory attached holding the four provided eyepieces (309,461 bytes).
Click on images to see a striking enlarged view (1,014,604 bytes).

Japan had become the butt of 1950’s quality control jokes, “made in Japan” was generally not considered a compliment. But Japan’s industries improved, they became innovators, and the Japan of the late 1960’s into the 1980’s came to dominate the production of small moderate to excellent quality optics including telescopes, cameras and microscopes. Unitron appealed to the more demanding clientele, a limited portion of the marketplace. And over the years Unitron was to stay loyal, one could argue mired, to their principles.

The aspect of their history in the USA commenced when United Trading Company acquired the rights to distribute the Nihon Seiko telescopes and their accessories. United Trading was founded by Lawrence Fine with offices and a shop at 204 Milk Street, Boston 9, Massachusetts. Soon after going into business United became United Scientific Co. and developed an acronym under which the telescopes might be more readily recognized, the trade name UNITRON.

Simultaneously the telescopes continued to be marketed in western block nations of Europe and most Commonwealth nations (Australia, New Zealand, etc.) under the trade names UNITRON and or POLAREX. In Japan and in some countries these sold under their trade name Seiko Scope; this particular 3 inch telescope is among those listed in the Nihon Seiko catalog under the Seiko Scope Equatorial series. Some smaller quantity production lots of telescopes were made by Nihon Seiko Kenkyusho under other trade names including WELTBLICK (World View), but these are not anywhere near as common as those bearing UNITRON or POLAREX trade names.

The astronomical telescopes product line offered initially included models built upon the 1.6" (40mm) and 2.4" (62mm) optical tube assemblies. The product line would include Altazimuth heads, German Equatorial heads, wood tripods for portable use, steel piers for permanent installation of the larger models, eyepieces and accessories. Gradually the line expanded to offer 2 inch (50mm) and 3 inch (75mm) models. In May 1953 the 4 inch (102mm) models were announced soon followed by the observatory class 5 inch (125mm) and 6 inch (150mm) optical tube assemblies.

New accessories and minor adjustments continued as the telescope line got its legs in the marketplace. In May 1955 “UNIHEX” was announced as the name for Unitron's new six position rotary eyepiece holder; the competition to come up with the name was won by three amateur astronomers and each was awarded a UNIHEX. While each entrant in the competition was sent as a gift The Nature of the Universe by Fred Hoyle.

Adjustments to the line included changes of minor accessories availability, and of designations. For example 2.4 inch models are usually referred to as 2.4 inch or occasionally as 60mm in the literature, but at least some of the telescopes of 1954-55 are engraved D 62mm F 900mm, by the mid 1950’s this would be changed and remain D 60mm F 900mm. Some earlier production telescopes may have no information about the telescope make or size on the lens front cell, only listing the basic UNITRON along with aperture and focal length on the focuser. In time the diameter, focal length, and UNITRON (or UNITRON) were painted onto the front cell in simple thin block lettering. But by the mid to late 1950’s the contemporary scheme of painting the front cell with this information, as is on our telescope, had become standard.

On our 1970’s production 3 inch telescope the provided objective lens covers slipped onto the front; these are embossed with UNITRON in lettering. The older telescopes might be a simple unmarked cover, or these could be a white painted cover with lettering in red (mid 1950’s). But in the late 1950’s Unitron settled into black with white painted lettering, this would be the norm through the late 1960s. Most were minor changes, but none that made one component or the other obsolete.

Given the limitations of the crown and flint glass available then, in order to provide good performance the better refractors made from the 19th through the mid 20th century are lengthy beasts, typically with focal ratios on the order of f/15. This is the ratio of their lens diameter to their focal length, hence 2.4 x 15 = 36 inches or about 900mm. So even our comparatively small Unitron Model 114 - 2.4 inch telescope is challenging to work around with when housed within a six foot diameter observatory dome, as we display it at Company Seven. While the even longer 3 inch f/16 equatorial telescopes, as featured here, stand so tall that they will just fit into a typical room.

There was little in the way of true innovation with the telescopes, Nihon Seiko accumulated wisdom from other accomplished makers then integrated these ideas into their production - and did so with class. What Nihon Seiko did manufacture was made after careful thought, with a high degree of precision, and made of appropriate materials smartly engineered to work well and save weight. Each component was assembled by caring craftsmen who obviously took pride in their work. Nihon Seiko developed an integrated system with a good selection of optional accessories. These accessories increased the versatility of the telescopes, while some of these items simply made it easier or more comfortable to use the telescope. These telescopes were produced in quantities large enough so that the economies of scale with Japanese labor allowed their prices to remain below that of the most highly regarded competing refractors (Zeiss, Goto, Tinsley, etc.). With numerous quality control steps throughout the process the factory insured every telescope made would be a garner admiration and confidence, as well as high performance for the new owner.

    One amateur posted a comment that nicely puts these instruments into perspective in contemporary times:

"Unitrons, you spend more time looking at them than you do through them"

Throughout production changes to the equipment were not arbitrarily made and so parts support remained excellent even beyond the formal demise of the telescopes distribution, for those who choose to restore any Nihon Seiko telescope. It is not uncommon to find parts bearing the various logos on one used telescope since especially in the years following the discontinuation of production owners salvaged parts from damaged telescopes. So for example one might find a POLAREX labeled 1980’s telescope with a 1950’s Seiko labeled lens cover and with other parts labeled UNITRON.

The first United advertisement announced their 1.6 and 2.4 inch aperture telescopes bearing the heading "At Last! - A Telescope You Can Afford!". This was submitted late in 1951 for placement into the October issue of Sky and Telescope, soon after this was followed by ads in other issues and in Scientific American magazines too.

United Trading Co. telescope advertisement 1951 (116,544)
At Last! - A Telescope You Can Afford!

Precision Refractors at
Unbelievably Low Prices
Three models to choose from. Each is made from the finest materials and imported
from one of the world’s largest manufacturers of optical instruments.

    - LENSES are FULLY CORRECTED for spherical and chromatic aberration and are COATED for maximum brilliance and clarity of image.
    - Each model is equipped with a sturdy TRIPOD and SLOW-MOTION device, low-power VIEW FINDER, STAR DIAGONAL, RACK AND PINION FOCUSING, TWO EYEPIECES, a SUNGLASS for solar observation, and comes complete with WOODEN CARRYING CASE. In addition an ERECTING PRISM SYSTEM for terrestrial observation in included with Models NS 114 and 128.
    - These accessories are included with your telescope.... There are no costly extras to buy. If these instruments were manufactured in this country, they would cost at least twice our low price.

204 Milk St, Sept. T-10, Boston 8, MAss
Fully Guaranteed
Telescopes Shipped Express Collect
25% deposit required on C.O.D. shipments

Above: Advertisement from October 1951 introducing the first three telescope models to the US Market.
The US distributor was then marketing as United Trading Co., before UNITRON became the registered trademark (116,544 bytes).
Click on image to see enlarged view ((192,267 bytes).

April 1952 announcement in <i>Sky and Telescope</i> Unitron introducing the Model 142 (98,669 bytes) In the April 1952 issue of Sky and Telescope Unitron introduced the Model 142, 3 inch Photo-Equatorial model as "Coming Soon"; the same ad appeared in the May issue. This half-page advertisement did not announce any pricing information about the new telescope, but the ad invited inquiries from prospective customers. The June issue of Sky and Telescope carried the nearly identical half-page advertisement mentioning the price of the Model 142 as $435.

Right: April 1952 announcement in Sky and Telescope Unitron introducing the Model 142 (98,669 bytes).
Click on image to see enlarged view (191,602 bytes).

A curious change between the two introductory advertisements and those subsequent ads that followed is that in the first two ads the Model 142 telescope is pointing to the right, while in following ads the same photo is reversed so that the telescope points to the left.

In time Unitron ads would appear in other publications too including Popular Mechanics and Science Digest too.

In 1952: the cost of this telescope set with two eyepieces and a standard diagonal (before the UNIHEX was available) was $125 plus shipping. This was a long time ago; President Harry S. Truman was still in office, the Korean War was still on. So to gain some understanding about the times and how the cost of this telescope compared to other typical expenses of 1952:

  • Cost of a new Unitron Model 114 - 2.4 inch telescope with simple Alt-Az mount = $125

  • Average cost of rent per month was $80.
  • The average cost of gasoline was 20 cents per gallon.
  • Average cost of a new car was $1,700.
  • The median family salary (wages before taxes) per week was $75.

In 1952 the Model 114 telescope cost the average household nearly two weeks salary! If we refer to the U.S. Government Consumer Price Index Inflation Calculator we see $125 in 1952 had about the same buying power as $1,029 in 2010, when this telescope arrived at Company Seven. Incidentally, the $585 of 1985 corresponds to $1,186 in 2010. So even their entry level telescopes were quite an investment for the average consumer.

The Model 142 telescope we display is better accessorized than the basic Model 145. Ours includes accessories that were not sold in the 1950’s, in fact the 3 inch telescopes were was not yet available in 1952. But if we consider the base price of the Model 145 telescope in 1956 for example, then we find:

  • Cost of a new Unitron Model 142 - 3 inch Equatorial Refractor telescope = $435 ($3,596.84 in 2011 per CPIIC)
  • Cost of a new Unitron Model 145 - 3 inch Photo-Equatorial Refractor telescope = $550 ($4,547.73 in 2011)

  • Average cost of rent per month was $88.
  • The average cost of gasoline was 22 cents per gallon.
  • Average cost of a new car was $2,100.
  • The median family salary (wages before taxes) per week was $85.60

In 1956 the Model 145 telescope cost the average household more than six weeks pre-tax salary!

credit card (39,593 bytes) By 1952 the first and only credit card in widespread use, Diners Card, had only about 40,000 card holders; this is a small percentage of the some 41 million families in the US at the time. So merchandisers offered other ways to help consumers buy their product. In 1954 Unitron instituted both their “Easy Payment Plan” and ̶Layaway Plan”. The offer

  • Easy Payment Plan: was a form of credit granted to customers who completed a simple credit application and were qualified by Unitron. These customers placed their order for a telescope accompanied with a minimum payment of 25 percent of the balance due. Optional accessories amounting to $50 or more could also be bundled into this payment plan. The customer received the telescope and accessories, then paid the balance due plus a 6 percent carrying charge over the next 12 month period. Customers who could pay the balance due in less than 12 months would receive a proportional refund of 4 percent of the original carrying charge. The first payment was due 30 days after the instrument was delivered, and if the customer sent payment for the remaining balance then no carrying charge would be applied at all.

    As explained in the 1956 catalog “If your choice is the UNITRON Model 152, the 4" Equatorial priced at $785, the required down payment is only $196.25 with 12 monthly payments of $52.”

  • Layaway Plan: the customer ordered the telescope but the order was held at Unitron. In the meantime the customer made payments (at least $10 each in the 1950’s) and when the total had been paid then the telescope would be sent to the customer. Aside from the cost of the equipment and shipping there was no additional interest, carrying charges or fees.

Getting The Points Across: During the mid 1950’s the most noteworthy competitors of Unitron’s refracting telescopes were the Newtonian style reflecting telescopes and parts including those made by Cave Optical Company, Criterion Co., Edmund Scientific. So in 1955 Unitron unveiled a new part of its sales strategy that included humorous cartoons lampooning those bulky and heavier telescopes, and some competing refractors too. These are a few of those cartoons drawn for Unitron sales literature by the talented and acclaimed illustrator Ken Muse (b. 28 Apr. 1925, d. 19 Jun. 2010):

mocking the inconvenience of the Newtonian telescope (38,353 bytes)
Mocking the inconvenience of
reaching the eyepiece of a Newtonian telescope
giving up bulky and heavy for easy to use (43,524 bytes)
Giving up awkward and heavy for
comfortable and easier to use
don't look through a Unitron (38,401 bytes)

Above: cartoons drawn in 1955 for the Unitron catalog and other sales literature by illustrator Ken Muse (38,353 then 43,524 and 38,401 bytes).
Click on images to see enlarged views (in order 204,980, 225,445, and 203,227 bytes).

Unitron developed comprehensive catalogs and hand-out literature focused on the more popular models. Unitron published their first Observers Guide and Catalog explaining each of their telescope models, their accessories, and with a brief observing guide for amateur astronomers. This was followed in 1956 by a revised and updated a forty-one (41) catalog that appeared similar but that also included customer testimonials and astrophotographs taken by Unitron owners. When we look at Unitron literature we are struck by the lack of information about the optical tubes and mounts weights and dimensions; it leaves us wondering how many people ordered a Unitron only to be shocked upon arrival by its size.

By the late 1960’s plans were in the works to build even larger observatory based instruments and the first of these was the 8" (200mm) model. The largest model was developed in the late 1980’s and these were the 225mm (8.86) telescopes.

The Unitron 3 Inch Equatorial Telescope
Unitron 3 inch (75mm) objective lens (49,728 bytes)
Objective Lens: Throughout the 1950’s and into the 1960’s many lens makers offered achromatic telescopes, but no other western bloc nation had a manufacturer that offered a telescope as well made and functional, so well accessorized, and with a price as moderate (given the performance) as these made by Nihon Seiko. The Nihon Seiko achromatic refracting telescope objective (front lens) employ an air spaced two lens, one group arrangement. The design derives from the Carl Zeiss E-Objektiv, a refinement of the original doublet achromatic lens that was developed by German optician Joseph von Fraunhofer (b. 6 Mar 1787, d. 7 Jun 1826). This lens employs one element made of BK7 (borosilicate crown) glass precisely matched to work with the SF10 (a high index flint) glass component. In order to attain acceptable performance the focal ratio is f/16.1, fairly long by todays standards. By the 1920’s Zeiss production included E-Objektiv 60mm telescopes similar to our Model 114 complete with gear driven altazimuth mounts, wood tripod, case, and in the customer’s choice of either f/14.2 (Telex Codeword Asedabais, No. 511071) and in f/17.5 (Asalven, No. 511071).

Right: Objective Lens of our Unitron 3 inch telescope. Note the aperture engraved reads 75mm, and has red anti-tampering paint (49,728 bytes).
The same lens may be found bearing the same lens information but with the Polarex trademark, these were usually sold outside the Americas.
Click on image to see enlarged view (195,976 bytes).

The two lens elements are kept apart at the nominal distance from one another by aluminum foil coated paper spacers. The three spacers are laid in at the edges and between the lenses, 120 degrees apart and have no perceptible adverse impact on performance. The spacer is of the thickness determined by the lens design prescription, but when looking at a lens outside the cell then at first glance it is hard to see any air gap between the lenses. The lens elements and spacers are carefully slipped into a cylindrical lens cell and this is all held together by a retaining ring, the retaining ring is held in place by three bolts. As an anti-tampering measure each is dabbed with red paint so that if anyone tampers with the screws then the paint will be marred thus voiding any warranty. Signs of tampering giving one pause to consider whether or not the lens orientation may have been changed so that it may no longer be working at its best. The entire lens cell slips onto the optical tube, and is bolted into place by surrounding flat head screws.

Chromatism: this achromatic lens design provides a good degree of perfection of color correction (chromatism) due to the two types of glass used. It is the type of glass used that largely determines how well the color correction can be, while it is the prescription and how well the manufacturing meets that prescription that determines the other aspects.

Egret image showing chromatism (124,684 bytes) When observing at moderate magnifications then the primary three colors of the spectrum will appear to be at focus to the eye. However, the two types of glass used to make theses lenses can only bring two of the three primary colors to focus since not all the wavelengths pass through the lens similarly. Achromatic objectives can bring either red and green or green and blue to focus. In this lens design red and green are at focus, while blue is slightly out. So when observing contrasting objects at very high magnifications such as the limb of the Moon, a bright star against a background of space, the dark branch of a tree contrasted against a light blue sky, then the areas where dark and light objects meet will appear with a slight violet halo. The planets for example do not appear as natural in color as they might with a more advanced apochromatic objective; Jupiter and Saturn appear a bit yellowish than when viewed through the achromat than with an apochromatic system (refractor or reflecting) where they may appear milky white.

In photography too, in color or even in monochromatic (black and white) imaging sharpness is undermined, and bright stars will appear a bit bloated. This caused by the halo of secondary color that does not focus within the same area of the disc as does the red and green components.

Left: zoomed-in Digiscope of an Egret taken with a pocket camera. Before zooming in onto the Egret the image appeared well, but just lacking some snap. As the camera zoomed in then the image shows chromatism (violet false color) more and more obviously, especially pronounced where light and dark areas contrasts exist. The violet cast overall and the color fringing come from the lens of the pocket camera used to take the picture (124,684 bytes).
Click on the image above to view enlarged close up of the Egret where the violet fringing will be more apparent (132,351 bytes).

Regardless, chromatism was a common issue for most refracting telescopes and telephoto lenses manufactured into the 1970’s since the apochromatic refractive systems up to this time were costly and complicated to make - and even the best of the time could not equal what was to follow.

Optical Performance Of The Unitron 3 Inch x 1,200mm Objective
Coma Spherical
40 nm 20 nm 2140 nm 0 nm 449 nm 590 nm 0 nm

Above: Table above expresses optical properties including color correction in Nanometers at various Fraunhofer color lines (C to G).
The G violet color is farthest from focus; this is why contrasting objects observed at high magnification appear with violet halo.

For additional information about where the Fraunhofer lines correlate on the spectrum see below:

Focal Ratio: as light passes through a glass lenses it is refracted, gradually bent by one lens so that it is no longer a parallel beam of light coming in from the distance but is tapering to a point within the telescope optical tube. As light passes through the first lens element it is again bent slightly by the air in the space between the lenses; note how stars twinkle as light passes through moving air layers of varying density. Then the light passes through the second element and is bent yet again. So light has to deal with four surfaces and an air space, in addition to passing through two elements of glass (Crown and Flint). The steepness of the curves of the glass impact the properties at the image plane, the point of focus. The steeper the glass curves are then issues can develop including curvature of field, spherical aberration where light from the edge of the lens may not come to focus at the same plane as light from near the center. There are modern techniques to deal with these issues (improved glass types, computer aided production of complex even aspheric curves, etc.) but up into the 1970’s lens makers preferred to keep the lens curves spherical and able to acclimate to temperature changes. This was accomplished by using thinner lenses with shallower curves thus resulting in longer focal ratios - and very long telescope tubes!

The Nihon Seiko lenses are so smoothly figured and polished to meet the nominal prescription that the final degree of spherical aberration of these Nihon Seiko achromatic lenses is quite good so visual images appear sharp and clear so any residual false color is not that problematic to the novice observer.

AR Coatings: prior to 1935 all refractive lenses were made with no protective or anti-reflection treatments; the bare glass was exposed to the air or cemented to other lens components. So up to this time a notable amount of the light (4 to 6 percent per surface) approaching a lens was reflected off each lens surface - front AND back too! Consider an easy example for a moment - what do you see when you walk by a window pane? Your reflection! There is enough light reflected off that glass surface so that you can discern the image. The same thing was happening in telescopes, eyepieces, camera lenses - but worse. Since optical instruments and lenses consist of multiple elements of glass, there was the tendency not only to reflect light off the first lens surface but also to reflect light back and forth between uncoated air-spaced elements in the system. This not only decreased overall light throughput, but often resulted in ghost’ or secondary images showing up on film or to the eye; an astronomer might be seeing a star in the field that was not really there.

Dr. Alexander Smakula (b. 9 Sep. 1900, d. 17 May 1983) led the team at the Carl Zeiss AG company at Jena that developed T-optic, the first anti-reflection coatings process devised for lenses. This was patented on 1 Nov. 1935 but kept a military secret throughout the following year. The first generations were a purplish tinted microns-thin layers of magnesium fluoride (MgF2) a metallic salt. When precisely applied in a vacuum chamber to the lens surface this reduces the amount of light reflecting off of a glass surface and thereby increases cumulative light throughput. These coating reduce undesirable reflections of light between glass elements thus increasing contrast and reducing the potential for ghost images. This was a noteworthy achievement in optics, and it kept Zeiss camera lenses and more sophisticated optics at the forefront of technology in the 1930’s. Initially only the more critical optics were treated, some of these are marked T for transparenz. Over time even optical lens components of devices intended for routine uses (eyeglasses, binoculars, etc.) were coated.

By the mid 1940’s the MgF2 coatings technology was implemented in routine production of most better optical components by manufacturers world-wide. The early Nihon Seiko telescopes predate their adoption of the MgF2 coatings, so when looking into the lens from outside the telescope one can see the whitish reflections clearly. Gradually the MgF2 antireflection coatings were adopted as the standard treatment for all their objective lenses, their eyepieces, and accessories (UNIHEX, DEUTRON, etc.). Some of these coatings may appear almost invisibly, given away only by a subtle violet tint while other lenses have a much more pronounced violet tint. We at Company Seven can not be sure of why there were differences, though we speculate it might have to do with changes of sourcing for parts or changes of coatings laboratories hired over time, or it could be a coater was inconsistent. We occasionally experience inconsistencies even today, particularly with some of the more sophisticated mirror and lens coatings.

The OTA Mechanical Aspects - This Is What A Refractor Should Look Like.

Nihon Seiko Model 132 - 4 inch Equatorial telescope profile (33,923 bytes) The optical tube assemblies of the Nihon Seiko telescopes, going back at least to the 1930’s, are fully constructed of rolled metal with cast focuser and front cells. The components have been painted in the traditional color schemes of black and white. Some very early examples with brass focusers for example may have left the factory in their natural finish. But the Nihon Seiko telescopes we usually see have a white painted optical tube with black painted front and rear cell, and focuser castings. The interior of the optical tube assembly from the inside of the slip-on Dew Shield, down the length of the baffled interior and focuser along with the provided extension tubes were painted with a flat black paint. This interior treatment contributes to the high contrast of these systems, systems where the background of space might appear as black as the blackest velour. The black dust cap (lens cover) slips onto the open Dew Shield, and this bears the UNITRON trademark in white on older models or has UNITRON molded into the front on later production models. Our 3 inch telescope and its 2.4 inch photo guide telescope covers have the embossed UNITRON.

Left: A profile of perfect proportions! Nihon Seiko (Unitron) Model 132 - 4 inch (102mm) Equatorial Refractor.
Note this shares the standard De-Luxe model focuser of our Unitron Model 142 telescope marketed in the USA (33,923 bytes).

The long focal ratio and precision machining of the optical tube and lens cell make it a fairly simple matter to assemble the mechanical components, install the lens, and have it be suitably collimated at the factory. Thus the smaller 60mm telescopes have no push pull lens cell or other means to adjust the lens alignment to the tube. The larger telescopes including our 3 inch model do feature collimatable a lens cell; this is also desirable because it facilitates removal of the objective lens for cleaning or transport and for precise installation.

The optical tubes of the early production small telescopes were bolted directly onto the mount saddle; this can be seen in the advertisement from 1952 shown above. These early production telescopes can be distinguished from later production (about 1955 and later) where the telescopes are attached onto the mount by means of detachable hinged mounting collar. Having mounting rings or a collar allows the user to loosen the collar enough to slide the OTA back and forth to compensate for changes of payload, this balances the instrument on the mount and results in smoother movement and less risk of damage if a clutch is accidentally loosened. The Unitron Model 142 in our collection employs the mounting collar.

Nihon Seiko sold telescope components to third parties too. One of the better known examples are the pale blue painted optical tube assemblies (OTA) sold by Don Yeier’s Brandon Company in the mid 1980’s. These 5 inch Brandon telescopes incorporate an f/8 standard Christen Triplet Apochromat objective lens (yes made by Astro-Physics Co.) mated to a shortened Nihon Seiko 5" telescope optical tube with the 2 inch focuser.

The Focuser: that was originally provided with our Model 142 telescope was upgraded by the original owner to the De-Luxe Focuser as he progressed into astro-photography. The De-Luxe Focuser was an upgrade offered for the Model 142 and Model 145 telescopes made since the 1950’s, later this focuser was provided as standard equipment on the Model 145 or could be purchased separately for other Unitron telescopes or by telescope-making amateurs for their project.

Either focuser is built upon a body made of cast aluminum and with a diagonal-cut rack and pinion drawtube arrangement that is smooth when clean in routine use. As provided it included an 36.2mm (1.4 inch) diameter focusing sleeve, this is an extension section to be pulled out of the drawtube as needed to reach focus. At the tip of the focusing sleeve is a friction sleeve into which 0.965 inch diameter eyepiece could be inserted. The friction sleeve could be replaced with one to accept 1.25 inch sleeve. Or the entire drawtube was removed to accept the UNIHEX with its own provided drawtube. The focuser body is painted black, and tastefully engraved with the engraving inlaid with white paint.

But to reach focus could be tedious since the focuser drawtube alone could not provide enough extension to accommodate as broad a range of accessories as was offered for these telescopes. So one needed to loosen the clamp at the end of the focuser drawtube (without letting the clamp fall off), then insert the appropriate focusing sleeve, then slide the focusing sleeve in or out of the drawtube and lock it in place (after you find the clamp that fell off) so that the accessory could then be attached and drawn in or out to reach focus by turning the pinion hand knob.

On the earlier production smaller telescopes, including our 2.4 inch Unitron, there is no drawtube lock provided. There is no way to quickly adjust the tension on the drawtube or the amount of effort needed to turn the pinion control knob. Most of these telescopes sold for astronomy were shipped with the smallest model of the UNIHEX, and this accessory alone adds some 3/4 lbs. (334 g) of pull on the drawtube, adding the eyepieces adds somewhat more. So one needs to rely on having the focuser pinion tension set so that it does not allow the drawtube to slide back (drawing the image out of focus) when pulled upon by heavy loads. The De-Luxe focuser of our Model 142 telescope incorporates provisions for locking the focus at any setting; a must for astrophotography, particularly when used with a heavy camera attached. The lack of a drawtube lock can be a deal breaker for anyone seeking to buy a Unitron and interested in astrophotography, so look for one of the focuser models that incorporate a focus lock.

The focus control knobs of these telescopes were originally precision machined out of aluminum alloy, then anodized into a natural metal finish. However, between 1959 and 1961 Nihon Seiko transitioned their telescopes models over to attractive yet still durable black plastic knobs.

In the 1950’s it became common to hear the term “Made In Japan” being associated in a derogatory way with products exported from Japan since many items originating from there early after the war were poorly made or inconsistent. In an effort to promote and improve Japanese made products for export the government established trade groups to police manufacturers of goods for export; those manufacturers who complied with the quality and consistency requirements of the association could have their products bear an approval certificate or sticker. There were optical police too, so the better telescope manufacturers of Japan were affiliated with the Telescope Inspection Institute, hence the focuser of most telescopes made from the 1960’s into the early 1980’s may bear a sticker reading either “JTII̶a; or “Passed, Japan Telescope Inspection Institute”. The latter is the sticker affixed to the original focuser of our telescope too.

original Unitron 3 inch telescope standard/ focuser (56,233 bytes)
Unitron 3 inch telescope De-Luxe focuser (60,799 bytes)

Above Left: The focuser that was originally provided with our own and with all earlier production Unitron Model 142 telescopes. This remains in our collection (56,233 bytes).
Click on image to see enlarged view (134,978 bytes)

Above Right: De-Luxe Focuser, ordered by the original owner and installed by him onto our Model 142 telescope, shown with drawtube extended and with the extension installed.
Note both setscrew locks. This is the type of focuser provided with the Unitron Model 145 telescopes (60,799 bytes).
Click on image to see enlarged view (213,237 bytes)

One final observation; when a customer ordered an upgrade focuser from Unitron then it was not always guaranteed that the focuser body would have the telescope information engraved. The original owner of this Model 142 ordered the upgrade focuser and received one with no telescope OTA information, hence unlike the original focuser shown above right that is labeled "D 75mm F 1200mm", while the De-Luxe focuser is only engraved with the UNITRON name.

Finder Telescope: this instrument was originally furnished with one 8x 30mm aperture finder telescope. The finder assembly is attached to the main telescope barrel by two brackets bolted onto the tube wall. Most telescopes that are comparatively high magnification designs are furnished with a smaller, wide field of view auxiliary telescope. With the 3 inch f/16 telescopes not being able to see any more than about 1.1 degrees field of view (about two diameters of the Moon), the finder is an essential aid to point the main telescope onto the target quickly. The original owner of this telescope realized that particularly when operating with a German Equatorial style mount, it is helpful to have at least one additional Finder telescope attached along the area opposite of the original 8x 32mm finder. So he ordered not only one optional larger 10x 40mm finder, he also ordered a second auxiliary 8x 30 finder.

Each cast aluminum bracket has three support screws used to tip and tilt the finder so that it is aligned parallel to the line of sight of the main telescope. To focus the finder pointed the telescope onto an easy to find distant object, while looking through the finder eyepiece rotate the eyepiece to focus the dual line crosshairs. Finally, focus the finder onto the distant object by pushing in or pulling out the eyepiece and drawtube assembly to reach focus.

Unitron Model 142 Mount Head roller bearings, main and worm gear, shaft, and other drive components (49,348 bytes) Mount Head and Tripod: among the attractive aspects of the entire product line was the value they provided with their attention to precision, rigidity, and appearance in the design of the mounts that support the telescope optical tube assembly. In these areas the Nihon Seiko products stood alone for decades. Nihon Seiko made German Equatorial Mounts and Altazimuth Mounts so most telescopes were offered in the customers choice of either mount. The mount heads are built upon machined aluminum castings that incorporated finely crafted roller bearings, worm and main gears, and other components of stainless steel. Customer who preferred a telescope dedicated to astronomy would not only have the choice of the telescope on a German Equatorial Mount, but also had the choice of more sophisticated Photographic Equatorial ensembles. The larger telescopes can barely be accommodated, even for static display without special consideration of their height. An even more impressive memory is seeing a large Unitron telescope set up and with an amazing array of finder/guide/auxiliary telescopes attached to (almost smothering) the primary telescope.

Right: Unitron Model 142 Mount Head Right Ascension axis main and worm gears set, roller bearings, shaft, and other components (49,348 bytes).

Competing systems then marketed to the consumer tended to incorporate less finely made gears sets, fewer precision bearings (if any at all), and their tripods tended to lack the rigidity of the products. While the Nihon Seiko mounts incorporated fine geared smooth controls, precise bearings, and clutches to allow precise manual control motions (up or down, left or right) of the mounts. One could set up the Nihon Seiko mount quickly, then track a planet across sky observing at high magnifications smoothly and with no jitter or point the telescope onto a distant ship and follow it across the horizon.

The equatorial telescopes were offered with a sturdy and attractive wood field tripod, these are fixed in their angle of leg spread. The tripod provided with the mounts made to support the telescopes of up to 3 inch were articulated, made to fold about in half for more compact stowage as is that of the Unitron Model 142 telescope we show. The larger 4 and 5 inch telescopes were offered with the choice of either the fixed height wood field tripod or with a metal pier for permanent installations; these legs too were provided with wood storage cases and could rival a telescope case in length overall. Later in production the tripod made to support some of late production 4 inch telescopes was made to fold in half too, similar to the storage arrangement of the smaller 3 inch tripods. The folding legs on a 4 inch Equatorial set are uncommon, this is another interesting aspect of the Model 132 telescope selected for exhibit at Company Seven. The 6 inch and larger telescopes mounts were offered only with the metal pier, there was no field tripod offered as they were not likely to be moved about.

For the customer who intended to use the telescope primarily for terrestrial applications and for casual visual astronomy then the altazimuth mount suffices. Furthermore, the altazimuth mount is simpler to set up and a less costly proposition. The altazimuth mounts were made available only with a matched portable wood field tripod. The wood tripod was intended to be folded quickly with the lower section rotating about the hinge at the middle of the leg, then rotating the lower section to store it neatly in between the upper leg spans. When extended the legs were supported in their proper disposition by means of a metal brace attached to the top of the lower section of each leg.

The mount included with the Model 142 telescope set is a German Equatorial mount with wood field tripod. Some of the details include the Setting Circles, and Clock Drive option:

Unitron Model 142 Mount Head Right Ascension Setting Circle (61,248 bytes)

Right Ascension Setting Circle: Resolution to 1 Arc Minute

Unitron Model 142 Mount Head Declination Setting Circle (69,645 bytes)

Declination Setting Circle: Resolution to 5 Arc Minute. Note the Decl. Axis lock/tensioning nut at the bottom, just above the Counterweight Shaft locking nut

Unitron Model 142 Mount Clock Drive Motor (34,569 bytes)

Clock Drive Motor, Linkage and Support Tray

Above: Unitron Model 142 mount details as it arrived at Company Seven; even after decades it inspires confidence and pride of ownership.
Click on images to see enlarged views (in order 187,530 then 185,918 and 199,956 bytes).

Assembly of the Mount and Telescope:

Extend the tripod leg extension sections, then attach the legs brace/accessory tray to keep the legs from accidentally spreading out under load. The tips of the tripod legs are of sharp and pointed steel, these will readily dig into the ground and stand fast. However, when setting up on very soft or wet ground Company Seven recommends placing a disc of plywood on the ground and under each leg tip to spread the load around a larger area. This will reduce the likelihood of the tripod settling in the ground, or even freezing into mud if the temperature drops through the observing session. For display indoors an optional caster pad under each tripod leg tip can protect your flooring.

We recommend setting up on level ground, alternatively you may put some block(s) under one or more legs to better level the set. Many owners employ a bubble level set onto or permanently affixed to the mount head, this to help judge when leveling. Next attach the mount head onto the tripod.

The Counterweight Shaft of the Unitron 142 mount head is an eleven (11) inch long fully machined bar, threaded ⅝ inch - 11 TPI (thread per inch) along its entire length. Of this about two inches threads into the female threaded socket of the mount head Declination Axis, leaving about nine inches extending from the mount to accommodate thread-on counterweights. Thread the Counterweight Shaft onto the mount, then secure the shaft in place by tightening the sole ⅝ inch - 11 nut against the Declination Shaft housing threads, this is at the point where the shaft enters the mount socket. Then thread the weights onto the shaft leaving the mount in a shaft-heavy configuration, at least to start off. Now the mount is ready for the telescope. This type of threaded rod is sold at most hardware stores, so it a simple matter to replace the shaft should you come across an incomplete Unitron mount. Even if you lack the original Unitron threaded counterweights you could drill a third-party counterweight to fit the shaft, then attach ⅝ inch - 11 nuts and washers above and below the slide-on counterweight.

Attach the telescope optical tube mounting collar onto the mount saddle (the topmost flat section of the mount), attaching this by means of two hand knobs. The telescope was set onto the collar and slid towards the front or back along the saddle until the optical tube reaches a nominal working balance point. Then swing the collar upper half down and over the telescope, secure the collar upper half to the lower half in place with the hand knob at the side of the collar.

The UNIBALANCE is a counter weight set made to balance the telescope along its Declination Axis, this resembles those sets historically provided for many refractors including those made by Carl Zeiss Jena for example. The UNIBALANCE set consists of a 13-¼ inch long x 0.3 inch (8 mm) diameter shaft with one threaded end that attach onto the fixture atop the UNICLAMP bracket. The set is provided with one sliding 337 g. (11.9 oz.) counterweight that can be locked at any position along the length of the shaft. Attach the UNIBALANCE set to the optical tube since this will facilitate changing accessories on the optical tube reducing the need to loosen the optical tube mounting collar to adjust the telescope position on the saddle.

Next loosen the clutches for Right Ascension and balance the telescope in that axis. Do the same for declination. To make fine adjustments in either axis first tighten the clutches, then turn the black hand knobs on either side of the rear of the mount head. The Right Ascension has a worm gear mechanism, so one can move the telescope throughout the RA axis with no interruptions, though care is taken to avoid binding the lengthy optical tube against the tripod. The Declination manual geared controls are spring loaded tangent style drives, and so the mount can only be moved so far by these controls without loosening the clutches to manually reposition the telescope, an unwinding the manual geared controls before resuming the tracking. When using the smaller Unitron Alt-Ax telescopes it was a simple matter while at the eyepiece to reach forward to turn these controls to track an object, but mounts such as this and for the 4 inch and larger telescopes incorporated flexible cables or steel rods to facilitate this.

Pole Aligning The Mount:

Proper operation of a German Mount requires the Right Ascension (R.A.) axis of rotation be aligned to be parallel to the axis of the Earth’s rotation. To achieve this at locations that you will frequent, Company Seven recommends you first level the tripod. By leveling when you first Pole Align the mount head you will not need to change the latitude setting of the mount again unless you travel north or south to other locations.

Loosen the azimuth (left to right, or longitudinal) adjustment clamp of the Nihon Seiko mount head assembly, this permits the user to smoothly rotate the assembly atop the field tripod and direct the mount head R.A. axis to point towards the Celestial North (or South) Pole. Then tighten this clamp. There is no fine adjustment mechanism to fine tune centering the mount in azimuth since the movement is smooth and can be refined easily enough.

Unitron 3 inch Photo Equatorial telescope mount latitude fine adjustment mechanism (66,794 bytes) Since this elevation adjustment motion involves working against gravity, the mount head is fitted with a latitude fine adjustment mechanism to attain a more precise pole alignment. The latitude adjustment mechanism consists of a hardened stainless steel threaded worm (male) and hexagonal sleeve (female), similar to a turnbuckle, to drive the mount head tilt up or down precisely.

Right: Model 142/145 German Mount with latitude adjustment mechanism circled (66,794 bytes). The installed set shown and circled in green accommodates operation at latitudes of between approximately 25 to 40 degrees, the shorter mechanism shown removed at right is for higher latitudes of Approx. 50 degrees.
Click on image to see enlarged view (183,869 bytes).

Adjusting the mount head tilt up or down when Pole Aligning involves first making certain the large stainless steel bolt that joins the Right Ascension axis housing to the mount head base post is adjusted just enough so that this joint may be articulated by hand but that this is not too loose either. When the mount head left the Nihon Seiko factory the nominal tensioning of this bolt would have been set. But if the mount had been used by someone doing astrophotography, or if used by someone not familiar with proper technique, then this bolt may have been tightened too tight to allow changing the latitude.

Next turn the latitude adjustment mechanism, this control can be turned by hand and is easier to do if while turning the hexagonal sleeve with one hand you gently support the telescope with your other hand doing so in a manner to reduce the load on the mount elevation bearing. The latitude adjustment mechanism has only a limited span of travel, this is dependent on the lengths of the two threaded components. So when the mount was sold new the distributor provided the appropriate mechanism for the user’s intended latitude. This was fine if you lived in one latitude range such as along the northern states of the USA or in the United Kingdom for example. But if you relocated to Florida for example, then you would need to change the assembly with one that is suitable for the lower latitude.

If you acquire a mount that is lacking the correct Nihon Seiko latitude adjustment components, a suitable replacement may be fabricated by a machinist with some guidance and using the original as a conceptual model. Alternatively one or two tripod legs can be shimmed, a wood block can suffice, to allow the mount head to reach the optimum tilt in latitude - of course insure this is not so excessive a tilt that the set becomes unstable.

The latitude adjustment mechanism is not designed for use near the Equator, nor could the mount be aligned in Arctic regions owing to interference between the Right Ascension setting circle and the mount head post.

Finally, the Setting Circles are indexed either by using reference stars or by other techniques.

Owing to the long length of the telescopes and fixed height of the tripod legs, people learned to work around the telescope standing when looking towards the horizon and possibly sitting on a low seat when observing objects overhead. This posed no major issues for most people and children when using telescopes of 3 inch and smaller. But by the time the design was scaled up to a 4 inch model, then when observing objects low in the distance shorter people would need to use a short step ladder to reach the eyepiece. But that is all part of the fun of having such a long optical tube to work around.

Unitron eyepieces including those provided with our Model 114 telescope

Eyepieces: a telescope is a light funnel that gathers light and forms one image. Eyepieces are basically magnifying lenses that are attached onto the focuser of a telescope to enlarge the image. The working magnification, numerous qualities of the image (field of view, clarity, degree of chromatism, etc.), and the comfort of the user while observing (eye relief) are determined not only by the qualities of the telescope but also of the eyepiece.

Right: five eyepieces provided with our Model 142 alongside two 2 inch diameter eyepieces for comparison in our display (95,568 bytes)
Click on the image to see enlarged view (100,004 bytes).

The eyepieces designs provided by Unitron included the Ramsden (sometimes termed Modified Achromatic), a design formulated in 1782 by scientific instrument maker Jesse Ramsden. The Kellner (designed b Carl Kellner in 1849) is another popular choice, basically an improved Ramsden. Both the Ramsden and Kellner are economical general purpose eyepieces that when made well satisfy most novices however, the Ramsden introduced perceptible false color that some people may wrongly attribute to originating in the telescope objective lens. Given the f/15 to f/16 focal ratios of the Unitron telescopes makes less demands of an eyepiece than faster designs, these eyepieces were suitable for most amateurs. For the more demanding clients there were optional Orthoscopic (design devised by Ernst Abbe of Carl Zeiss in 1880) eyepieces available too. The Orthoscopic is highly regarded for its uniformity of magnification (lacking distortion) across the entire field of view when used with systems of f/7 and longer. When made well the Orthoscopic provides superb contrast and definition thereby making it an optimum choice for high resolution applications including observing the planets, double stars, the Moon, etc.

The UNITRON 1.6, 2.4, and 3 inch telescopes could accept interchangeable eyepieces of either 0.965 or 1.25 inch in diameter, although the standard four eyepieces provided with the set were 0.965. The 0.965 inch standard was referred to as the “Japanese” standard in some literature however, this standard was typical for telescopes made in the late 19th and early 20th centuries and predated Japan’s involvement in optics.

When originally introduced the 60mm Altazimuth telescopes were sold for $125 and furnished with two 0.965 inch diameter eyepieces: the 9mm and 18mm. The standard drawtube tip fitting would accommodate 0.965 accessories (diagonal, etc.). By 1956 most of the telescope sets, including the 3 inch model shown here, were provided with a set of four eyepieces as standard equipment: 9mm Achromatized Symmetrical, 12.5mm Kellner, 18mm Kellner, and 25mm Huygens. Telescopes equipped (as this one) with the UNIHEX or with a 1.25" diagonal would accept one optional 1.25 inch eyepiece. By 1963 Unitron included a new Achromatic Amplifier with the telescopes, this is a negative or Barlow lens that could be attached onto the barrel of the UNIHEX or the standard extension sleeve. When installed the Achromatic Amplifier increased the effective focal length of the telescope by a factor of about 2x, thus doubling the magnification of each eyepiece.

By the late 1980’s most new amateur telescopes, even introductory models, were built to accept at least 1.25 inch diameter eyepieces. Companies including Celestron that offered “Cometron” series telescopes with 0.965 targeted to the entry level consumer found the American customer and reviewers showed disdain for the old reliable standard in favor of the larger 1.25 inch eyepieces. The more advanced amateur and professional telescopes (not that too many professional astronomers ever look through a telescope anymore) incorporate focusers that can accept the even larger 2 inch diameter eyepieces. The attraction of the larger and larger eyepieces has to do with: 1. the potential for wider fields of view, and 2. improved eye relief.

In addition to magnification and quality of the image presented, the eyepiece determines the actual field of view; the area that can be seen. The field of view most accurately can be calculated when knowing diameter of the opening within the eyepiece barrel where the telescope image plane and eyepiece planes meet (Field Stop). Company Seven’s measurements of Unitron eyepieces show how the differences in maximum area that can be observed compare among the three popular eyepiece standards:

  • 2 inch diameter eyepiece can show as much as 2.9x the area seen in a 1.25 inch eyepiece, or 5x the area of a 0.965 eyepiece
  • 1.25 inch diameter eyepiece shows 1.7x the area of a 0.965 inch eyepiece
  • 0.965 inch eyepieces can show almost two thirds the area that can be seen in 1.25, and one fifth the area that can be seen in 2 inch eyepieces

As the industry changed to 1.25 eyepieces the sources of 0.965 eyepieces (Carton Optical Industries Ltd. for example) gradually discontinued production of the older standard. By this time telescope sales at Unitron were winding down anyway so there was no need to source new stock of the 0.965 eyepieces. By the mid 1980’s Unitron offered a greater selection of 1.25 inch diameter eyepieces than they offered 0.965 inch models.

M40 eyepiece profile from Company Seven archives (20,747 bytes) Optional eyepieces in the Unitron line from 1955 included: 0.965 - 4mm Orthoscopic, 0.965 - 5mm Orthoscopic, 0.965 - 6mm Orthoscopic, 0.965 - 7mm Achromatized Symmetrical, one 1.25 inch eyepiece the 40mm Kellner-Monochro*, and one 2 inch 60mm Kellner. While the provided focal lengths of the eyepieces never varied by much over the years the mix of models varied slightly, for example in most years the provided 25mm was a Kellner but later this was substituted for with a Ramsden. The offerings varied somewhat over the years but the choices for the larger telescopes in particular included 2 inch diameter eyepieces including their 60mm Kellner, the upscale 55mm Plossl and 32mm Erfle wide angle eyepieces. By 1985 the 2 inch offerings continued to show only one, the 60mm Kellner, being available. But by the mid 1980’s none of these eyepieces could compete for the attentions of dedicated observers against superior and more versatile eyepieces by competitors, most notably Brandon and Clave as well as the innovative TeleVue Optics.

    * this was a 1.25 inch diameter 40mm Kellner-Monochro eyepiece, because of this larger diameter barrel it could be employed on the 3 inch and smaller aperture telescopes only with the UNIHEX attached.

Left: One of the more interesting eyepieces ever distributed by Nihon Seiko in profile (20,747 bytes). From design in Company Seven’s Archives.

Each air spaced element was treated with magnesium fluoride anti-reflection coatings to improve light throughput and to reduce the possibility of ghost images. Later production telescopes featured slightly improved multilayer antireflection (AR) coatings, usually presenting with a greenish ting. The AR coatings subdue undesired reflections, otherwise it was possible to have one brighter star reflect back and forth between eyepiece elements thus giving the misleading appearance as though there were other stars in the field of view. The curves of these lenses are so subtle that ghosting could only rarely become a concern in practice. The interior of each eyepiece barrel is painted anti-reflection black.

While the provided focal lengths of the eyepieces never varied over the years, the mix of models varied slightly. For example in most years the provided 25mm eyepiece was a Kellner design but this later this was substituted for with a simpler Ramsden design eyepiece. The telescope in Company Seven’s collection was acquired with the original five 0.965 inch diameter eyepieces (described below).

Eyepieces Offered By Unitron Exhibited at Company Seven:
Unitron 0.965 and 1.25 inch diameter eyepieces provided with telescopes exhibited at Company Seven Unitron 2 inch diameter eyepieces acquired for exhibit at Company Seven
                • Field of View is actual field of view as calculated for our Unitron 3 inch refractor based on our eyepiece design data and testing.
                • Unitron 2.4 inch 3 inch refractor telescopes could accept only 0.965 inch diameter eyepieces, or 1-1/4 inch eyepieces with the UNIHEX.
                • Our Unitron 3 inch Model 142 telescope included five .965 inch eyepieces: R25mm, K18mm, K12.5mm, SYM ACH 9mm and SYM ACH 7mm.

                • The ER32 eyepiece was made to either slip fit into 2 inch port of a Super UNIXEX or thread-on to the Super Focuser drawtube.
                • The 55 Plössl eyepiece was made to slip fit into 2 inch port of a Super UNIXEX.
                • The ER32 eyepiece was made to either slip fit into 2 inch port of a Super UNIXEX or thread-on to the Super Focuser drawtube.
                • We missed adding the K.13mm eyepiece to the set for the photo shoot, sorry.

Make Model Dia. Mag. Design Field of View
UNITRON MONOCHRO.40mm 1.25" 30X Mononchromat 1.13°
UNITRON # MONOCHRO.40mm 1.25" 30X Mononchromat 1.13°
UNITRON R25mm .965" 48X Ramsden 0.76°
UNITRON K18mm .965" 67X Kellner 0.52°
UNITRON K13mm .965" 92X Kellner 0.60°
UNITRON K12.5mm .965" 96X Kellner 0.38°
UNITRON K12mm .965" 100X Kellner 0.38°
UNITRON SYM. ACH. 9mm .965" 133X Achromatized Symmetrical 0.29°
UNITRON SYM. ACH. 7mm .965" 171X Achromatized Symmetrical 0.22°
UNITRON OR 6mm .965" 200X Orthoscopic 0.19°
UNITRON OR 4mm .965" 300X Orthoscopic 0.16°
UNITRON K60 25X 2" Kellner 1.52°
UNITRON 55mm 27X 2" Plössl 1.45°
UNITRON ER32mm 61X 2" Erfle 1.28°