Unitron and the Mystery of the Green Lens
by Steve Franks

A Crown Jewel Unitron 4" Objective

The business waters had been placid and inviting for Unitron in the 1950s and 1960s when the company had no real competition in the refractor market. Indeed, Unitron expanded and prospered with its iconic line of high-end, quality refractors. 

But the 1970s brought several competitors to the fore. It seemed every major department store around the country began to offer some kind of refracting telescope. People could now buy a reasonably well made, entry level refractor up to 75mm (3") from Sears & Roebuck, Crowley's, Macy's, Montgomery Ward or Gimble's at a modest price. Names such as Tasco, Monolux, Mayflower, and Swift appeared in increasing number at catalog and large chain stores. Even house brands began to appear like Sear's Discoverer made by Towa, for example. These telescopes were manufactured in Japan and surprisingly well-crafted with aluminum tube assemblies, cast mounts, and remarkably good glass optics. They often included their own wooden cabinets.

The fierce competition from these Japanese made imports, and from American makers of other types of telescopes forced Unitron to fight for market share for the first time. They dropped their 1.6" model 127, and greatly increased the price of others like the 2" model 114 from $125 to $165! 

Unitron and its Japanese parent company, Nihon Seiko, continued to lose market share as the 70s rolled on. In-house cost cutting measures [at Nihon Seiko] began to affect quality control. The consequence of which some of their instruments began to suffer. Looking for cheaper outsourcing of its objective lenses caused some telescopes to be sold with serious astigmatism and spherical aberrations. Dealers reacted harshly with complaints and returned lenses. 

Realizing it was imperative to maintain their public image and restore faith among its dealership, Unitron [Nihon Seiko] looked for new and credible sources for their objective lenses like Jaegers, Nikon, or Pentax who knew how to make excellent objective lenses.

The Mystery of the Green Lens
The first Unitrons had barely perceptible coatings on their objectives. My model 142 3” objective, c.1954 for instance, looks uncoated except under the closest scrutiny. For the next thirty years a light blue, single-layer 1/4 wave, anti-reflective Magnesium Fluoride coating became the norm. The coating improved light transmission of these lenses from about 84% to 96%. But 1980 ushered in a spate of mystery objectives on their 4" models cast in a deep green tint. This lens was introduced as part of a newer style 1980s Model 150 4" alt-azimuth refractor. 

This dark green coating is believed by many to be the hallmark of the house of Pentax whose custom, at the time, was to coat their lenses with a 1/2 wave layer of Magnesium Fluoride. The characteristic dark green coatings are multi-layer coatings involving a more costly process. The end result is that they improve the light transmission to 98%. 

It is possible the green coated Unitron lenses were made from a different refractive index glass than earlier ones, hence the need for a greater thickness coating? 

It is interesting to note that these green coated 4" objective lenses also sported a serial number beginning with 5000. Respected sources has it that the #5000 series was from a small batch of especially good glass. Simon Brown, formerly of Unitron, had estimated that there were probably less than 100 of these made, most likely not more than 75.

Those who have had the ability to critically evaluate these mystery Unitron objectives rank them among the finest doublets ever manufactured. According to John W. Siple, of the Rose City Astronomers, optical designer Mike Palermiti confirmed his belief that Unitron [Nihon Seiko] subcontracted out some of its 4" f/15 objective lens orders to Pentax who cast, figured, and multi-coated them. It was they who likely memorialized this small batch with serial numbers. Unitron never bothered applying serial numbers to their own instruments.

John W. Siple, who chronicled Unitron's history with more than a few articles, devoted much time trying to trace the provenance of these first-rate objectives and uncovered the following facts in 2004:

1.)  They were produced in the early 1980s.
2.)  Less than 100 were ever placed on Unitron telescopes.
3.)  The majority are of 4" aperture.
4.)  There is a concentration of them in the Midwestern states, especially Michigan, where several major Unitron dealers were located.
5.)  The #5000 series will outperform other Unitron 4" objectives from the same time period. 
6.)  Rumor has it that the #5000 series was from a batch of especially good glass.
7.)  The #5000 series objectives increase the value of a Unitron refractor by, at least, $500 due to their rarity and superb optical quality.
8.)  Only one green coated 3" f/16 objective from the 1980s has appeared on the marketplace, and it was a replacement objective lens for a damaged original lens.
9.)  To date, less than 10 such #5000 series objectives are known, scattered throughout this country.
10.) 2.4" or 5" objectives with #5000 series numbers have never appeared.

Just Playing With the Numbers
It should be noted that to find a 3" f/16 lens with a #5000 serial number engraved on the inner cell is very unlikely (like winning the lottery), since Unitron sold far more 3" refractors than 4" models. However, it appears the odds of getting one were fairly high in the 1980's when the basic 3" model 142 was priced at an exorbitant $2000. 

According to Barry Simon (founder and moderator of the Yahoo/Unitron forum), Unitron sold (est.) 25,000 units in its forty-year history of telescope production. So far, [the known] upper limit on #5000 serial numbers is 5058. Therefore only (58)/(25,000) X 100 = 0.23%, or 1 in 430 telescopes may have an inner cell marked with a serial number. 

And, if Barry Simon's guess about the number of 4" Unitrons made in the company's forty-year history is correct (a few thousand), this makes the 5000 series a rarity indeed. A ROUGH percentage would be (100/2000) X 100% = 5%. This means that (approx.) 1 in 20 4" Unitrons might have a serialized pedigree. 

To Summarize
One of Unitron's subcontractors (many believe Pentax) in late 1979, or early 1980, produced an especially fine glass mix with ideal optical properties for that era. It is agreed that this batch produced some the finest performing objective lenses Unitron had ever sold. A greenish multi-coating was placed on these objectives, and the inner cell was marked with a #5000 sequential serial number. The #5000 series objectives have long been considered Unitron's "Crown Jewels" in optical performance. Only 1 in 430 Unitrons, in their forty-year history, has such a pedigree. A serialized objective adds at least $500 to the overall value of a Unitron refractor.

The Plot Thickens 
John W. Siple's investigations in 2004 determined that this particular run of Unitron objectives was in the early 1980s since all units sold appeared in the early to mid-1980s. However, my 160 4” Unitron was purchased July 1980 and it has a serialized objective number 5053. This shifts the production date to more likely around 1979. This would allow for the necessary lead time for Nihon Seiko to receive the objectives, assemble and package the telescopes, crate, and ship the finished telescopes from Japan to Unitron in New York.  

Long after the very lively Yahoo/Unitron forum discussions about the mysterious green objective in 2004, I have discovered a model 152 Unitron with the serial number 5061 in December 2014. This extends Barry Simon's original upper limit of serialized lenses by three more objectives. It is owned by a Mr. K. Hooper, an amateur astronomer, in Arkansas. We now know for an absolute fact that at least sixty-one lenses exist. Not fifty-eight.

I have had a 3" Unitron tube assembly in the back of my closet for about twenty-seven years waiting for some unmaterialized project. In November 2013, I purchased a used (c.1954) model 142 3" Unitron. It was only then I discovered the old OTA possessed a green tinted objective! Comparing it with the 142’s original lens, which is very good, proves it to be the most perfect objective lens I have ever seen. But it bares no serial number. A few other green tinted objectives, sans numbers, have been reported. All were sold in the late 1980s. It is rather doubtful they are from the original batch. Could these have been from a second and unmarked batch by the same source? Though unmarked, these lenses appear to be just as perfect as the serialized objectives. 

And, when we speak of Unitron throughout this story we must remember it was actually Nihon Seiko, the Japanese firm that made the instruments imported to the USA under the name Unitron. So if it was actually Nihon Seiko who did the subcontracting, what of their European Unitron counterparts marketed as Polarex? Do any green tinted Polarex objectives exist? Are they serialized? 

Were the serialized, green coated lenses, in fact, made by Pentax as many believe? Until  some hard evidence like an old invoice turns up, that may have to remain a part of the Unitron mythology. 

Storyline by Steve Franks - 2014

sfranks2@sbcglobal.net

References:
Classic Telescopes - Neil English
https://groups.yahoo.com/neo/groups/UnitronTelescopes/info