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This site contains a personal collection of astronomy images taken with various astronomical instrument in selected locations around the world.
"Astronomers say the universe is finite, which is a comforting thought for those people who can't remember where they leave things."—Woody Allen
"With every passing hour our solar system comes forty-three thousand miles closer to globular cluster M13 in the constellation Hercules, and still there are some misfits who continue to insist that there is no such thing as progress."—Ransom K. Ferm.
REFRACTORS
In today's amateur astronomical refractor market, we have seen a wide variety of such instruments offered, ranging from affordable achromats to exquisite, albeit expensive apochromats. Here, I will seek to discuss how the refractor market has evolved over the last decade(s) and also talk about the merits and character of these optical instruments.
The dawn of the telescopic instrument market for "hobbist" astronomers started in the late 1800s when a couple of English and Continental telescope makers, steming from family-based businesses, produced small refractors and reflectors for sale to the market, that came with simplistic tripod mounts and a selection of accompanying eyepieces. In the United States, an up-and-coming optical company, Alvan Clark and Sons (See footnote * on a little history), began to offer a line of amateur refractors mostly in the 2.4 to 4-inch aperture range, but at the same time offering bigger models up to 8-inches in diameter. Similarly, the company sold these with mounts, tripods, and eyepieces.
These mainstream Clark refractors were of simple yet nicely figured doublet achromats. As such, chromatic aberration is an inherent issue with these telescopes, however, the later generations of these refractors can still be found to this day, manifesting as the classic festive Christmas telescope with simple optics but poor build quality. Sadly, this also leads to the single most common cause of a rapid diminishing loss of interest in the hobby by the child who gets one for a present, or the parent(s) who tries to handle these telescopes. The Clark tradition of building a good but simple achromat for the American amateur market continue after the Second World War, with emerging companies such as Unitron (note that Alvan Clark and Sons closed its operation after the war was concluded), and again primarily manufacturing 2.4 to 3.5-inch aperture refractors. The accompanying simplistic mounts and eyepieces have also not advanced significantly over the Clark products of the turn of the previous century.
Today, these achromatic refractors (compared to the Christmas telescopes) can be had cheaply from a number of optical companies who market them, complete with modern coatings and improved mechanical features from several sources in China.
The real successors of Alvan Clark and Sons are the handful of small operations such as D and G, Unitron, and Parallax Instruments. They would offer the traditional long focal length achromats, in sizes up to and sometimes slightly larger than 8-inches of aperture. These long, but relatively light refractors are the last vestiges of the traditional high-end achromatic refractor market. With the now modern coatings inherent in such refractors, boasting hand figured accuracy adhering to the most current optical specifications, these telescopes produce great images with only a hint of false colour, which is often minimized further by special (but relatively inexpensive) optical filters. Unfortunately, such refractors are fast becoming rare and near extinction.
While there will also be a place for simple achromats, given price advantages for the novice or amateur astronomer on a strict budget, or those who want a larger aperture at a competitively reasonble price, they are no longer in the mainstream market anymore. These achromats are also becoming more and more rare not because of any inherent design flaw, especially when one considers the price trade-offs. D and G still has a waiting list for the classic, long focal length 4- inch ahcromats, in contrast with no wait lines for many reasonably priced and decent 4-inch ED refractors. The real reason for the emergence of the now popular apochromats (as the new darling of amateur astronomy) is the inherent benefits of their ability to provide colour-free (or close there to) views in a much shorter package, and therefore easier to mount and transport. A 4-inch F/20 achromatic refractor should provide a relatively colour-free view under all but the most extreme circumstances. But how long and cumbersome would that refractor be when a competing 4-inch F/6 apochromatic refractor will perform as well or even better, and get more use since it will be far easier to handle and transport during any observing session. Like it or not, it is clearly recognizable that today's apochromatic refractors have the advantage in every area other than price or perhaps nostalgia.
In another area, there was also the ATM movement, which begain to blossom in the United States back in the 1920s, eventually brought the reflector into widespread use, but it was a slow process.
For the source of the current 'state of the art' refractors, we would need to head to Germany during the period after World War I. The German optical industry has a long, and well-justified reputation for skill, innovation, and perfection of design and production of carefully crafted high-end products. In cameras and camera lenses, the names, Leica and Zeiss stand out above most others. These companies were the inspiration for and 'copied' and then matched and sometimes 'bettered' by several Japanese optical firms, including Canon, Nikon, Pentax and others. And, as with Zeiss, several of these Japanese companies also developed superb optics intended for amateur astronomers, following the lead of Zeiss.
In the years after Word War I, Zeiss introduced a growing line of amateur optics, lens cells, and complete telescopes for the optics market. Originally high -end achromats, very much in the Clark mode of operation, using its own research in the development of optics for the scientific and government markets, Zeiss introduced the first apochromats to be commercially available in any 'production series'. Today, these refractors can still be found, albeit rarely and at a very dear price, as the Zeiss APQ series (See footnote *2 on prior refractors made by Zeiss other than the APQs). These APQ apochromats were fluorite-based triplets built to the very highest standards (note that Zeiss also built superb doublets as well). Using what was then the most advanced scientific testing methods, each optical set was vigorously tested before release.
Indeed, quality control was maintained at the very highest level by Zeiss and this affirmed their subsequent reputation in the optics market. It was ever mentioned by a long-time Zeiss employee that each APQ refractor was given its final test by a senior optician who took every telescope out to check its performance on the night skies. If the refractor did not meet his standards, regardless of preliminary test reports, it would be rejected in the most emphatic manner as he would put it on a bench and smash it with a hammer! It was believed that Zeiss would never take the chance of having a single sub-standard refractor with its name on it and leaving the factory.
The Zeiss APQ series was limited up to 6-inches of aperture. This largest of all the Zeiss apochromats, if it appears on the market today, commands a healthy five figure price tage and even then rarely lasts on the market for more than a day. And the fact that the APQ is still not that far behind as compared to today's apochromats, is a tribute to its excellence when completed.
The Zeiss APQs are the ancestors of today's apochromats. Several current designers trained in the Zeiss 'school' with Roland Christien at the Astrophysics building upon this heritage, both as to design and emphasize on the highest possible standards of optical performance and strict quality control. These same principles also found their way into the early Japanese apochromats, which would be discussed next.
What is still relatively little known is that the Japanese optical industry also produced not only the infamous 1950s and on 'Christmas Trash Telescopes' - this was pre-China trade days - but also some serious and superbly designed refractors, almost like the Zeiss APQ series. The Japanese companies, especially Nikon, produced a similar product line to Zeiss, mostly very nice doublet achromats or better corrected semi-ED types, which were sold locally or under other labels for the world export market.
Nikon and Pentax also built a series of outstanding ED doublets, including the Nikon 100/1200 that offered optics that were figured by a master optician that many believed was a close match to the finest built anywhere in the rest of the world. Refractor reviewers such as Ed Ting and others later tested these long focal length ED refractors and were astonished at the views and the figure accuracy of these lenses. Optical tests performed on these then out-of-production lenses showed the visual impressions were accurate, the Japanese opticians who carefully crafted these optics produced world class products just as they had done with their camera lenses, now the standard by which others must be judged.
Alas, Nikon left the amateur optics market with its 4-inch masterpiece refractor. The last vestige of Nikon in the field was their 120mm large, fork mounted binoculars, an alternative to the just a bit large but just as spectacular Fujinon 125x150. Those too are no longer in production.
Another Japanese early entrant into the amateur refractor market was Pentax. Like Nikon, Pentax began in the camera field before it begain to produce refractors. Their production has always been larger than Nikon, with this company showing far greater interest in this market. Similar to Nikon, Pentax offered a line of ED doublets that were just as well designed and produced. Unlike Nikon, they have remained in the market for a longer period, only until recently that they stopped production of their refractors entirely. They have produced state of the art apochromats ranging in sizes from 75 to 125mm in aperture. Their optics are, again, superb but also very expensive, with the Nikon tradition of fine craftmanship followed which results in a product that is priced accordingly. Their 75mm has a built quality that makes it a work of art and a pleasure to simply hold and to look at. Looking through it provides on eof the finest example of a 3-inch apochromat, and excels particularly as an imaging tool.
Pentax also offered some 100 and 125mm refractors that are equally well- built with optics that are just as fine. They were sold in small quantities all over the world primarily as imaging platforms.
The Japanese company that will be next discussed in this section is Vixen. While there are a number of other Japanese manufacturers who also produced refractors, they never exported under their own name in significant numbers and no longer survive or have left the market. Vixen, however, is still with us and still active. Vixen has long produced a very broad range of products for the amateur astronomy market. In addition to long standing product of refractors ranging from 'Christmas Trash Telescopes' (and rarely under the Vixen label when these toys were built in Japan before Taiwan and later China took over) to very well-built ED doublets and fluorite doublets up to 5-inches in aperture. Vixen has and continues to build reflectors, and binoculars in a very large variety. The scale of Vixen's production, both as Vixen and for many years under the Orion label in the United States, matches and exceeds all of the other Japanese makers and is second to only Meade and Celestron.
Vixen quality has always been good, although in my opinion, never matching the Pentax or Nikon refractors. The pinnacle of Vixen's refractors were the fluorite doulets that topped out at 100mm and today still command a good price in the second-hand market. Vixen deserves praise for offering these excellent telescopes and the 'lesser' refractors as a reliable source to our community of sound, carefully built and inspected products.
Today, Vixen has stepped back a bit from the top range of the market. The fluorite series is no longer in production. Many of the Vixen products are now manufactured for them in China. Only a few of their refractors are built in Japan, and even then, whether their optics are produced in Japan or simply assembled there after they are built in China is an open question. Their telescopes today are a solid value, but no better optically than most other ED doublets with perhaps slightly better mechanical 'fit and finish'. Nonetheless, an early Japanese maker that had a substantial hand in building today's market.
That leaves one very unique Japanese company to deal with in the next section, one that has carved out a significant place in this hobby and one that continues to offer superb and sometimes unique refractors, Takahashi.
Takahashi is known to the domestic Japanese market and the greater world to be a reputed high-quality apochromatic refractor maker. Some has matched its optical and mechanical excellence to that of the Nikon and Pentax refractors, or perhaps even better. In the earlier days (1960s, 1970s), Takahashi produced semi- apochromats which were mostly long focus in nature, thereafter producing the back then, legendary of its time, the FC series of refractors which were based on the Steinheil design and utilized fluorite glass (technically it is in crystalline form!). This design required a thick and heavy rear fluorite element since the Steinheil design had steeper curvature of radii. The steeper curves may also have led to the increase of spherochromatism of the design for a given focal length.
The FC series was then subsequently further revised and taken over by the current FS series (Fraunhofer design), whereby with its less steep curvature of radii, the fluorite element used was less expensive (as compared to the older FC series). However, the use of the Fraunhofer design in the FS series (with the fluorite element placed in front) did require Takahashi to start using a hard- coating on the fluorite element to protect it, presumably adding some expense to its production. The FS 128 and FS 152 were then stopped in production and was replaced by the TOA triplet series - TOA 130 and TOA 150. As to why there was a this TOA series, it might have been due to economic production reasons for these larger aperture apochromatic refractors. That the continual use of fluorite crystal (which is about five times more expensive per weight than FPL glass) proved to be a challenge in polishing successfully as fluorite is soft and fragile. Takahashi has thus chosen FPL53 glass (from the manufacturer Ohara) for use in its TOA series since it is cheaper than fluorite and these TOA triplets allow for faster refractors and better colour correction in the violet end of the light spectrum for CCD imaging.
Lastly, Takahashi also made the petzal quadruplet FSQ series for 106mm aperture, and lately a 85mm version which excelled superbly in visual and imaging applications. These telescopes were known for its high contrast character and versatility in imaging.
Footnote *: Alvan Clark and Sons began from a skilled and self-trained former portrait artist who then taught himself to make and figure refractor lenses. His sons worked with him and outlived him slightly. The family business brought in some talented help, especially the Lundins, father and son team who survived into the early 20th Century when others took over until the company folded along with the end of World War II. There were even smaller companies Brashear, Fecker, Tinsley, Mogey, etc) who did not even have a 'line' of standard, commercially available telescopes and mounts, and their productive output was always strictly based on a 'one off' or build-to-order business, on a much smaller scale.
Footnote *2: A long-time before Zeiss came up with the APQ refractor series, there was the AS refractors, called Astro Spezial, which were designed by August Sonnefeld back in 1926. It consisted of a doublet objective with a KzF2 front element and a BK7 as the rear element. This design was manufactured from 1926 up to 1994. Zeiss made several sizes: 63/840, 80/840, 80/1200, 100/1000, 110/1650, 130/1950, 150/2250, and 200/3000. Note that the first number is the aperture and the second is the focal length, both measured in millimetres. Reference found in Jurgen Kosts webpage but is in the German language. Zeiss also built a far larger number of achromats and semi- apochromats (early ED styled doublets) that survive in large numbers even till today. Examples of these can be seen at Markus Ludes, APM website.