Download Document 9044958

http://www.company7.com/library/unitron/unitron_142.html
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 of the Model 142 in
Company Seven's museum display collection of telescopes.
Contents and Quick Links: click on the to return to top of this article
History: Start Of The Space Age
d: Who Were Unitron, Polarex, Nihon Seiko?
Specifications Of This Telescope
n 3 Inch Equatorial Telescope
Pertinent Documents and Literature In Our Archives
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
since the beginning of the Space Age.
Company Seven had been keen to acquire a Unitron 2.4 inch alt-az and a Unitron 3 inch
equatorial telescope for our display since these are among the few landmark production
telescopes that gave thousands of people their introduction to visual 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 moreso 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 productionUnitron
Model 132 - 4-inch (102mm) Equatorial Refractor telescope to our exhibit, and this is
displayed alongside our Model 142/145 for comparison.
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.
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 altazimuth 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 also offered the 3 inch
telescope with the German
Mount, the Model 145 set was
marketed as the 3 inch PhotoEquatorial 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 3-1⁄16 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.
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.
Item
Pri
ce
In
195
6
Pr Pri
ice ce
in in
19 198
74 5
Model
142, 3"
Equato
$43 61 1,2
rial
5.0 4. 98.
Telesc
0 00 00
ope
cased
set
Model
145, 3"
PhotoEquato
rial
Telesc
$55 90
ope
0.0 5. N/A
cased
0 00
set
listed
for
compa
rison
only
DeLuxe
Rack
15
$15
10.
&
.5
.50
00
Pinion
0
upgrad
e
UNIH
EX A
35
$24
80.
.2
.75
00
5
DEUT $23 41 84.
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)
RON
A
.50
.0
0
00
Secon
d 8x
30
21
Finder $10
65.
.5
(Incl.
.75
00
0
Mount
ing
Rings)
10x 40
Finder
33
(Incl. $18
90.
.7
Mount .00
00
5
ing
Rings)
Synchr
onous
Motor
11
Drive $60
167
5.
115v, .00
.00
00
with
hardw
are
2.4"
photo
guide
Telesc
12
$81
230
ope
3.
.00
.00
(Incl.
00
Mount
ing
Rings)
Extra
Counte
rweigh
t to
Balanc $4. 9. 15.
e
75 80 00
photo
guide
Telesc
ope
ASTR
15
$69
O5.
.50
CAME
00
N/
A
RA
220
UNIB
ALAN
CE
26
Tube
$15
57.
.0
Weigh .50
00
0
t
Syste
m
3"
UNIC
LAMP
Piggyb
14
$3.
31.
ack
.7
75
00
Camer
5
a
Bracke
t
Sun
Diago
nal
(Hersh
el
$17 29
63.
Wedge .50 .0
00
),
** 0
0.965
inch
Model
A
Sun
Diago
nal
(Hersh
$22 37
el
95.
.50 .2
Wedge
00
** 5
), 1.25
inch
Model
B
40mm
MON
21
OCHR $14
38.
.0
O,
.75
00
0
1.25
inch
eyepie
ce
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.
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.
Above: Unitron 3 inch Photo Equatorial telescope optical tube assembly wood case (76,172 and 90,386 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).
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.
At Last! - A Telescope You Can Afford!
Precision Refractors at
Unbelievably Low Prices
Three models to choose from. Each is made from the finest materia
from one of the world’s largest manufacturers of optical inst
- LENSES are FULLY CORRECTED for spherical and chromatic
COATED for maximum brilliance and clarity of image.
- Each model is equipped with a sturdy TRIPOD and SLOW-MOT
VIEW FINDER, STAR DIAGONAL, RACK AND PINION FOCU
EYEPIECES, a SUNGLASS for solar observation, and comes com
CARRYING CASE. In addition an ERECTING PRISM SYSTEM
observation in included with Models NS 114 and 128.
- These accessories are included with your telescope.... There are n
If these instruments were manufactured in this country, they would
low price.
UNITED TRADING CO.
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).
In the
April
1952
issue
of Sky
and
Telescop
e Unitro
n
introduc
ed 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 pretax salary!
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):
king the inconvenience of
yepiece of a Newtonian telescope
Giving up awkward and heavy for
comfortable and easier to use
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
Self-explanatory
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
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.
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
Aberrration
40 nm
20 nm
Chromatic
Aberration:
G
F
E
D
C
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:
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.
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.
Mount
Head and
Tripod: a
mong 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:
g Circle: Resolution to 1 Arc Minute
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
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:
Clock Driv
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 weight set made to
balance the telescope along its Declination Axis. The UNIBALANCE set consists of a
13-½ inch long x 5/16 inch diameter shaft with 5/16-18 TPI threaded ends that attach
onto the tube brackets. The set is provided with one sliding 670 g. (1 lb. 7.7 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.
Since
this
elevation
adjustme
nt 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.
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.
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: